Composites and Alloys Based on the Al-Ce System

*David Weiss*

## **Abstract**

Aluminum alloys containing small amounts of cerium have been investigated to improve the grain refining, casting characteristics, and mechanical properties of aluminum alloys. These additions were usually made at levels of 1% or less but did not produce appreciable improvements. Recent work has shown that additions between 4% and the approximate eutectic composition of 10% improve the high-temperature performance of aluminum alloys. Corrosion performance of aluminum alloys can also be improved through the addition of Ce. Traditional aluminum alloying elements such as magnesium and silicon can be used to control casting characteristics and thermal and physical properties. Cerium oxide is the predominate oxide in rare earth mining. Much of it is discarded after separation from the heavy rare earth oxides containing Nd and Dy. The beneficial use of Ce should reduce the cost of the more desirable rare earths. Results of using Ce as an addition to aluminum in multiple manufacturing methods such as additive manufacturing, extrusion, and casting are explored. The results show significant strengthening and improved mechanical property retention at higher temperatures than in other aluminum alloys and, in some compositions, show complete recovery of mechanical properties at room temperature when exposed to elevated temperatures as high as 500°C for 1000 hours.

**Keywords:** aluminum-cerium alloys, aluminum-cerium composites, casting, extrusion, additive manufacturing

### **1. Introduction**

Auto manufacturers are under commercial and regulatory pressure to improve engine efficiency. Potential solutions include direct fuel injection, higher compression ratios, and turbochargers. All these solutions can cause higher operating temperatures and pressures. Al-Si-Mg or Al-Si-Cu-Mg alloys, typically solution treated and aged, are used for automotive products because of their good mechanical properties at room temperature and easy processing. However, these alloys rapidly lose strength above their aging temperature, typically around 155°C. For engines to be able to operate between 180 and 300°C, a different paradigm for alloy design is needed. The requirement for high-temperature lightweight alloys is not restricted to automobile components. Aerospace and military sectors, as well as commercial sectors such as trucking and industrial equipment, all require alloys that meet the increased demands of new fuel-efficient designs.

Several strategies have been employed to improve the performance characteristics of aluminum alloys. The addition of Cu generally improves both room temperature and high-temperature strength, although there can be an impact on corrosion

because of a greater change in electrode potential with variations in the amount of copper in solid solution and the presence of nonuniformities in solid solution concentration [1]. The addition of transition metals such as Zr, Mn, and V is being used to stabilize the precipitates in alloys of the Al-Cu-Mg and Al-Si-Mg system. Many types of metal matrix composites have been developed that will generally improve modulus, yield strength, and elevated temperature properties although the composites are generally less ductile and are more difficult to process.

Cerium addition can improve the performance characteristics of both solid-solution-strengthened and precipitation-strengthened aluminum alloys, particularly at elevated temperatures.

## **2. Background and history**

Mondolfo [2] reviewed the aluminum-cerium and the aluminum-ceriumiron system and reported that small additions of Ce do not produce appreciable improvements and that the alloys did not have a wide application. He reported that a eutectic is formed with 13% Ce at 638°C. In a later work [3], he reported that an increase of strength without loss of conductivity and improved machinability had been claimed for cerium additions to aluminum alloys. He referenced sources that claimed an Al-CeAl4 eutectic at approximately 12% Ce.

An analysis of the Al-Ce-Fe system produced via powder metallurgy showed extraordinary strengths in an Al-8Fe-4Ce alloy at temperatures up to 343°C [4]. There was no documented attempt to cast these materials.

There has been some experimental work to use Ce as a component of cast aluminum alloys. Shikun [5, 6] reviewed the effect of cerium additions on the cast microstructure and solidification range of an Al-4.5Cu alloy. He concluded that the addition of cerium improved castability but the mechanical properties were not studied. Belov [7] explored Ce for the development of creep-resistant aluminum alloys in combination with transition metals such as Zr, Mn, Cr, Fe, and Ni. Later [8], Belov focused on the Al-Ce-Ni system. He concluded that alloys of the Al-Ce-Ni ternary eutectic system had high mechanical properties at room and elevated temperatures along with good casting characteristics.

Al-Si alloys are the most important Al-based foundry alloys. They have good mechanical properties, narrow solidification ranges, and good fluidity. Gröbner [9] considered aluminum alloys containing up to 25 at.% Ce and 45 at.% Si and studied several Al-Ce-Si systems where the aluminum was held at a constant 90 at.% and the concentrations of Ce and Si varied between 0 and 10%. He showed that small Ce additions could provide high-temperature stable AlCeSi phases in equilibrium with Al-Si-rich melt. He concluded that Ce between 1 and 5 at.% could be used as a grain refiner.

The development of Al-Ce casting alloys is driven by the increasing demands for high-temperature-tolerant aluminum alloys and the use for the excess cerium that was available as a by-product of the production of the heavy rare earths.

### **3. Metallurgical aspects of the Al-Ce system**

The equilibrium diagram, Ce-Al crystal structure data, and Ce-Al lattice parameter date were reviewed in 1988 [10], and a eutectic composition of Al and Al11Ce3 was shown at 4 at.% Ce at 640°C. This reference confirms the Al-rich compound had previously been incorrectly identified as Al-CeAl4. Recently calculated Thermo-Calc data predicted a eutectic of Al11Ce3 at 580°C at 10 wt.% [2.09 at.%] [11].

**59**

**Figure 2.**

*Ce solubility in aluminum.*

**Figure 1.**

*Composites and Alloys Based on the Al-Ce System DOI: http://dx.doi.org/10.5772/intechopen.89994*

Al2Cu in 200 series.

Typical microstructures of the Al-Ce binary composition are shown in **Figure 1** [12]. The as-cast microstructures show a very fine interconnected Al11Ce3 eutectic microstructure in a pure aluminum phase. The intermetallic can be as small as 50 nm wide at permanent mold cooling rates. These structures are stable up to the melting point of the aluminum phase. The intermetallics cannot dissolve since Ce has extremely low solubility in the aluminum matrix. A solubility diagram for the binary Al-Ce system is shown in **Figure 2**. Yield strength retention is about three times conventional alloys when tested at 300°C. When Ce is used with solid solution strengthening elements such as Mg or Zn, room temperature properties remain stable regardless of exposure times with exposure temperatures up to 400°C. The data in **Figure 3** shows an actual increase in room temperature properties after exposure at 400°C. This is due to the homogenization of magnesium that is not uniformly distributed because of low and variable cooling rates in the cast structure. In solid-solution-strengthened alloys, there are no phases that dissolve or coarsen such as the Mg2Si in 300 series alloys or the

Load partitioning studies in compression conducted by Oak Ridge National Laboratory at their Vulcan Beam Line show unusual load sharing behavior between the matrix and the Al11Ce3 intermetallic. As illustrated in **Figure 4**, as the compressive stress increases, a higher proportion of that stress is transferred to the intermetallic. An extensive analysis of the strengthening mechanisms and microstructural

*(A) As-cast microstructure of Al-Ce8 binary alloy. (B) Al-Ce8 binary showing sub-micron width laths.*

analysis of the Al-Ce system can be found in Ref. [11].

*Composites and Alloys Based on the Al-Ce System DOI: http://dx.doi.org/10.5772/intechopen.89994*

*Aluminium Alloys and Composites*

particularly at elevated temperatures.

claimed an Al-CeAl4 eutectic at approximately 12% Ce.

There was no documented attempt to cast these materials.

temperatures along with good casting characteristics.

**3. Metallurgical aspects of the Al-Ce system**

**2. Background and history**

because of a greater change in electrode potential with variations in the amount of copper in solid solution and the presence of nonuniformities in solid solution concentration [1]. The addition of transition metals such as Zr, Mn, and V is being used to stabilize the precipitates in alloys of the Al-Cu-Mg and Al-Si-Mg system. Many types of metal matrix composites have been developed that will generally improve modulus, yield strength, and elevated temperature properties although the

Mondolfo [2] reviewed the aluminum-cerium and the aluminum-ceriumiron system and reported that small additions of Ce do not produce appreciable improvements and that the alloys did not have a wide application. He reported that a eutectic is formed with 13% Ce at 638°C. In a later work [3], he reported that an increase of strength without loss of conductivity and improved machinability had been claimed for cerium additions to aluminum alloys. He referenced sources that

An analysis of the Al-Ce-Fe system produced via powder metallurgy showed extraordinary strengths in an Al-8Fe-4Ce alloy at temperatures up to 343°C [4].

There has been some experimental work to use Ce as a component of cast aluminum alloys. Shikun [5, 6] reviewed the effect of cerium additions on the cast microstructure and solidification range of an Al-4.5Cu alloy. He concluded that the addition of cerium improved castability but the mechanical properties were not studied. Belov [7] explored Ce for the development of creep-resistant aluminum alloys in combination with transition metals such as Zr, Mn, Cr, Fe, and Ni. Later [8], Belov focused on the Al-Ce-Ni system. He concluded that alloys of the Al-Ce-Ni ternary eutectic system had high mechanical properties at room and elevated

Al-Si alloys are the most important Al-based foundry alloys. They have good mechanical properties, narrow solidification ranges, and good fluidity. Gröbner [9] considered aluminum alloys containing up to 25 at.% Ce and 45 at.% Si and studied several Al-Ce-Si systems where the aluminum was held at a constant 90 at.% and the concentrations of Ce and Si varied between 0 and 10%. He showed that small Ce additions could provide high-temperature stable AlCeSi phases in equilibrium with Al-Si-rich melt. He concluded that Ce between 1 and 5 at.% could be used as a

The development of Al-Ce casting alloys is driven by the increasing demands for high-temperature-tolerant aluminum alloys and the use for the excess cerium that

The equilibrium diagram, Ce-Al crystal structure data, and Ce-Al lattice parameter date were reviewed in 1988 [10], and a eutectic composition of Al and Al11Ce3 was shown at 4 at.% Ce at 640°C. This reference confirms the Al-rich compound had previously been incorrectly identified as Al-CeAl4. Recently calculated Thermo-Calc

was available as a by-product of the production of the heavy rare earths.

data predicted a eutectic of Al11Ce3 at 580°C at 10 wt.% [2.09 at.%] [11].

composites are generally less ductile and are more difficult to process. Cerium addition can improve the performance characteristics of both solid-solution-strengthened and precipitation-strengthened aluminum alloys,

**58**

grain refiner.

Typical microstructures of the Al-Ce binary composition are shown in **Figure 1** [12]. The as-cast microstructures show a very fine interconnected Al11Ce3 eutectic microstructure in a pure aluminum phase. The intermetallic can be as small as 50 nm wide at permanent mold cooling rates. These structures are stable up to the melting point of the aluminum phase. The intermetallics cannot dissolve since Ce has extremely low solubility in the aluminum matrix. A solubility diagram for the binary Al-Ce system is shown in **Figure 2**. Yield strength retention is about three times conventional alloys when tested at 300°C. When Ce is used with solid solution strengthening elements such as Mg or Zn, room temperature properties remain stable regardless of exposure times with exposure temperatures up to 400°C. The data in **Figure 3** shows an actual increase in room temperature properties after exposure at 400°C. This is due to the homogenization of magnesium that is not uniformly distributed because of low and variable cooling rates in the cast structure. In solid-solution-strengthened alloys, there are no phases that dissolve or coarsen such as the Mg2Si in 300 series alloys or the Al2Cu in 200 series.

Load partitioning studies in compression conducted by Oak Ridge National Laboratory at their Vulcan Beam Line show unusual load sharing behavior between the matrix and the Al11Ce3 intermetallic. As illustrated in **Figure 4**, as the compressive stress increases, a higher proportion of that stress is transferred to the intermetallic. An extensive analysis of the strengthening mechanisms and microstructural analysis of the Al-Ce system can be found in Ref. [11].

#### **Figure 1.**

*(A) As-cast microstructure of Al-Ce8 binary alloy. (B) Al-Ce8 binary showing sub-micron width laths.*

**Figure 2.** *Ce solubility in aluminum.*

#### **Figure 3.**

*Long-term exposure data of Al-Ce alloys measured at room temperature compared to some standard casting alloys.*

#### **Figure 4.**

*Phase load sharing for Al-12Ce-0.4 Mg under compressive load. Shaded region denotes differences between binary and ternary alloy composition's mechanical response from Ref. [4].*

#### **4. Alloying element interactions**

At room temperature, the Al11Ce3 intermetallic is not an effective strengthening mechanism. Mechanical properties for pure binary compositions are shown in **Table 1**. To develop reasonable room temperature strengths, other alloying elements such as Mg, Zn, Cu, Si, or others can be added along with Ce to strengthen the aluminum matrix. Sun [13] reported on a comprehensive study of 19 binary systems of Ce and 4d or 5d transition metals using high-throughput first-principles calculations. Understanding the reaction mechanics between Ce and other alloying

**61**

**Figure 5.**

*diffusion.*

**Table 1.**

*Composites and Alloys Based on the Al-Ce System DOI: http://dx.doi.org/10.5772/intechopen.89994*

corrosion, as shown in **Figure 7**.

*Mechanical properties of Al-Ce binary alloys.*

elements can be used to identify elements that could independently strengthen the aluminum matrix without interference from the Ce as well as those that form compounds with the Ce that can synergistically increase the strength or potentially

In commercially pure aluminum, magnesium in solid solution gives a near-linear concentration dependence of strength at a given strain. The solid solution hardening is a result of an interaction between the mobile dislocations and the solute atoms [14]. In an Al-8Ce alloy, the addition of 10% magnesium increases the yield strength by over 300% from about 50 MPa to about 162 MPa. There is no evidence that the formation of some CeMg intermetallic is a significant factor in the strength increase, with the primary mechanism being the matrix strengthening by the magnesium. The addition of copper to the alloy forms immobile Cu-Ce phases. This is illustrated in **Figure 5** using a 4.5% Cu alloy with the addition of 1 and 8% Ce. Most of the Cu is not free to strengthen the alloy since it is tied up with the Ce phase. On the other hand, the modification of the traditional grain boundary phases improves the hot tear resistance of the alloy and reduces intergranular corrosion. Additional Cu needs to be added to create "free Cu" that can participate in heat treat response. For copper-containing alloy such as A206 (**Figure 6**), the cerium acts as a diffusion barrier, preventing the formation of copper-depleted zones. In all alloys tested, the addition of small amounts of cerium increases their resistance to intergranular

Al-16Ce 144 68 2.5 Al-12Ce 163 58 13.5 Al-10Ce 152 50 8 Al-8Ce 148 40 19 Al-6Ce 103 30 25

*As cerium addition moves from 0 to 8%, the cerium phase dominates grain boundary phases and restricts Cu*

**Tensile MPa Yield MPa %E**

immobilize elements required for strengthening during heat treatment.

*Composites and Alloys Based on the Al-Ce System DOI: http://dx.doi.org/10.5772/intechopen.89994*

*Aluminium Alloys and Composites*

**60**

**Figure 4.**

**Figure 3.**

*alloys.*

*Phase load sharing for Al-12Ce-0.4 Mg under compressive load. Shaded region denotes differences between*

*Long-term exposure data of Al-Ce alloys measured at room temperature compared to some standard casting*

At room temperature, the Al11Ce3 intermetallic is not an effective strengthening mechanism. Mechanical properties for pure binary compositions are shown in **Table 1**. To develop reasonable room temperature strengths, other alloying elements such as Mg, Zn, Cu, Si, or others can be added along with Ce to strengthen the aluminum matrix. Sun [13] reported on a comprehensive study of 19 binary systems of Ce and 4d or 5d transition metals using high-throughput first-principles calculations. Understanding the reaction mechanics between Ce and other alloying

*binary and ternary alloy composition's mechanical response from Ref. [4].*

**4. Alloying element interactions**

elements can be used to identify elements that could independently strengthen the aluminum matrix without interference from the Ce as well as those that form compounds with the Ce that can synergistically increase the strength or potentially immobilize elements required for strengthening during heat treatment.

In commercially pure aluminum, magnesium in solid solution gives a near-linear concentration dependence of strength at a given strain. The solid solution hardening is a result of an interaction between the mobile dislocations and the solute atoms [14]. In an Al-8Ce alloy, the addition of 10% magnesium increases the yield strength by over 300% from about 50 MPa to about 162 MPa. There is no evidence that the formation of some CeMg intermetallic is a significant factor in the strength increase, with the primary mechanism being the matrix strengthening by the magnesium.

The addition of copper to the alloy forms immobile Cu-Ce phases. This is illustrated in **Figure 5** using a 4.5% Cu alloy with the addition of 1 and 8% Ce. Most of the Cu is not free to strengthen the alloy since it is tied up with the Ce phase. On the other hand, the modification of the traditional grain boundary phases improves the hot tear resistance of the alloy and reduces intergranular corrosion. Additional Cu needs to be added to create "free Cu" that can participate in heat treat response. For copper-containing alloy such as A206 (**Figure 6**), the cerium acts as a diffusion barrier, preventing the formation of copper-depleted zones. In all alloys tested, the addition of small amounts of cerium increases their resistance to intergranular corrosion, as shown in **Figure 7**.

#### **Table 1.**

*Mechanical properties of Al-Ce binary alloys.*

#### **Figure 5.**

*As cerium addition moves from 0 to 8%, the cerium phase dominates grain boundary phases and restricts Cu diffusion.*

The addition of scandium to Al-Ce alloys has been investigated [15]. At levels of 0.4% Sc, room temperature hardness levels increased by 20%, and room temperature hardness values after 300°C exposure for 100 hours increased by 60%. While the ternary Al-Ce-Sc had good thermal stability, the room temperature hardness values are not sufficient for structural castings. The addition of Mg at levels of up to 12.15% resulted in significant improvement in hardness at room and elevated temperatures.

Silicon as an alloying element in the Al-Ce system can be used to control the coefficient of thermal expansion, but the additions at higher levels cause several processing issues. While increasing the silicon in a binary composition with aluminum will reduce the solidification range up to the eutectic composition, the addition of Ce will increase that range which may make the alloy more difficult to feed in traditional casting applications. The solidification range of a standard Al7Si alloy is approximately 70°C. It was experimentally determined using thermal analysis that as the ratio of Ce to Si in an alloy is increased, the solidification range increases as

**Figure 6.** *The addition of Ce to Al-Cu alloys acts as a diffusion barrier by blocking grain boundary motion.*

**63**

**Figure 8.**

*Composites and Alloys Based on the Al-Ce System DOI: http://dx.doi.org/10.5772/intechopen.89994*

**5. Composite potential in Al-Ce alloys**

with 7075-T6.

a composite matrix material.

**6. Product forms**

well. At a Ce/Si ratio of 3.16, the solidification range increases to 120°C. At a Ce/Si ratio of 0.46, that solidification range is reduced to 82°C. Generally, maintaining a Ce/Si ratio of about 0.5 results in an alloy with excellent castability. The Ce will also form CeSi phases making some of the Si unavailable for combining with Mg when added to form Mg2Si strengthening precipitates. However, Si-rich alloys contain

In conventional hard particle-reinforced aluminum alloys, failure at elevated temperature can occur when the matrix softens and causes particle decoherence. Secondarily, the aluminum loses stiffness at high temperature, minimizing the modulus improvement attempted by the introduction of high modulus particles. Alloys containing Ce retain a higher percentage of modulus at elevated temperatures. **Figure 8** shows the modulus retention of an Al10Mg8Ce-F alloy compared

Preliminary work has been completed using SiC and carbon nanotubes as reinforcement in AlCe and AlCeSi alloys as well as Al2O3 in AlCeMg alloys. The addition of 50 nm Al2O3 at reinforcement levels of about 0.1% results in a tensile strength improvement of 12%. As shown in **Figure 9**, a substantial number of particles are in the grain and are not exclusively pushed into the grain boundaries. Particles in the grain enhance Orowan strengthening by resisting dislocation passing in the presence of closely spaced hard particles. Whether this is directly due to the cerium content of the alloy or other processing techniques is unknown. More data and functional testing is required to fully understand the use of Al-Ce alloys as

Much of the early work in the Al-Ce system concentrated on casting alloys.

The casting characteristics of the binary Al-Ce systems are as good as the aluminum-silicon system but can change as additional alloying elements are added [16]. When other alloying elements are used such as silicon, magnesium,

*Comparison of room temperature and 350C modulus between Al10Mg8Ce-F and 7075-T6.*

enough excess Si that the response to heat treatment is not affected.

*Composites and Alloys Based on the Al-Ce System DOI: http://dx.doi.org/10.5772/intechopen.89994*

*Aluminium Alloys and Composites*

The addition of scandium to Al-Ce alloys has been investigated [15]. At levels of 0.4% Sc, room temperature hardness levels increased by 20%, and room temperature hardness values after 300°C exposure for 100 hours increased by 60%. While the ternary Al-Ce-Sc had good thermal stability, the room temperature hardness values are not sufficient for structural castings. The addition of Mg at levels of up to 12.15% resulted in significant improvement in hardness at room and elevated temperatures. Silicon as an alloying element in the Al-Ce system can be used to control the coefficient of thermal expansion, but the additions at higher levels cause several processing issues. While increasing the silicon in a binary composition with aluminum will reduce the solidification range up to the eutectic composition, the addition of Ce will increase that range which may make the alloy more difficult to feed in traditional casting applications. The solidification range of a standard Al7Si alloy is approximately 70°C. It was experimentally determined using thermal analysis that as the ratio of Ce to Si in an alloy is increased, the solidification range increases as

**62**

**Figure 7.**

**Figure 6.**

*ASTM G110-92(15) intergranular attack test; submerged in hydrogen peroxide with NaCl.*

*The addition of Ce to Al-Cu alloys acts as a diffusion barrier by blocking grain boundary motion.*

well. At a Ce/Si ratio of 3.16, the solidification range increases to 120°C. At a Ce/Si ratio of 0.46, that solidification range is reduced to 82°C. Generally, maintaining a Ce/Si ratio of about 0.5 results in an alloy with excellent castability. The Ce will also form CeSi phases making some of the Si unavailable for combining with Mg when added to form Mg2Si strengthening precipitates. However, Si-rich alloys contain enough excess Si that the response to heat treatment is not affected.

### **5. Composite potential in Al-Ce alloys**

In conventional hard particle-reinforced aluminum alloys, failure at elevated temperature can occur when the matrix softens and causes particle decoherence. Secondarily, the aluminum loses stiffness at high temperature, minimizing the modulus improvement attempted by the introduction of high modulus particles. Alloys containing Ce retain a higher percentage of modulus at elevated temperatures. **Figure 8** shows the modulus retention of an Al10Mg8Ce-F alloy compared with 7075-T6.

Preliminary work has been completed using SiC and carbon nanotubes as reinforcement in AlCe and AlCeSi alloys as well as Al2O3 in AlCeMg alloys. The addition of 50 nm Al2O3 at reinforcement levels of about 0.1% results in a tensile strength improvement of 12%. As shown in **Figure 9**, a substantial number of particles are in the grain and are not exclusively pushed into the grain boundaries. Particles in the grain enhance Orowan strengthening by resisting dislocation passing in the presence of closely spaced hard particles. Whether this is directly due to the cerium content of the alloy or other processing techniques is unknown. More data and functional testing is required to fully understand the use of Al-Ce alloys as a composite matrix material.

## **6. Product forms**

Much of the early work in the Al-Ce system concentrated on casting alloys. The casting characteristics of the binary Al-Ce systems are as good as the aluminum-silicon system but can change as additional alloying elements are added [16]. When other alloying elements are used such as silicon, magnesium,

#### **Figure 9.**

*Fifty nm alumina particles in a matrix of AlMg10Ce8 alloy. Large white particles are aluminum oxide formed during melt processing.*

or copper, the solidification range is determined primarily by the secondary alloying elements. Standard systems for melting, degassing, and alloy cleaning of cast alloys can be used without modification for the conventional casting of aluminum-cerium alloys.

At solidification rates typical of castings in Ce alloys that contain more than 7% Mg, a homogenization heat treatment can be used to improve mechanical properties [17]. This treatment reduces the size and volume fraction of magnesium pools that can segregate in high magnesium alloys. The amount of cerium does not affect the segregation behavior. The alloys have been cast successfully in most traditional casting processes, such as sand, permanent mold, low pressure permanent, and die casting. **Figure 10** shows a cylinder head poured as a gravity casting showing the good fluidity of the alloy system.

Mechanical properties for the ternary Al-Ce-Mg system have been studied at both room and elevated temperatures (**Table 2**). The room temperature properties can be improved by both homogenization and hot isostatic pressing. One of the key attributes in the Al-Ce-Mg system is the recovery of mechanical properties at room temperature when exposed to elevated temperatures for prolonged periods of time. This alloy system does not contain any precipitates that become unstable after prolonged high-temperature exposure.

Extrusions have been produced for applications where improved high-temperature performance or resistance to corrosion is desired. In these alloys, extrusion improves the properties through a combination of work hardening and alignment of the intermetallic. Extrusions have been produced at 300°C billet temperature and at extrusion ratios of 5.75–1 and 52–1 from an Al10Mg8Ce alloy. A comparison of average permanent mold properties to extruded properties is shown in **Table 3**. As the extrusion ratio increases, tensile strength remains constant, with the elongation increasing and yield strength decreasing. The mechanical properties can be affected by the starting microstructure of the billet. Structural extrusions have also been produced as shown in **Figure 11**.

**65**

**Table 3.**

**Table 2.**

**Figure 10.**

*Composites and Alloys Based on the Al-Ce System DOI: http://dx.doi.org/10.5772/intechopen.89994*

*Air cooled cylinder head poured from Al-Ce binary alloy.*

*Room and elevated temperature properties of Al-10Mg-8Ce compared to common piston alloys.*

*Comparison of extruded data at different extrusion ratios with cast Al10Mg8Ce.*

*Composites and Alloys Based on the Al-Ce System DOI: http://dx.doi.org/10.5772/intechopen.89994*

#### **Figure 10.**

*Aluminium Alloys and Composites*

aluminum-cerium alloys.

**Figure 9.**

*during melt processing.*

good fluidity of the alloy system.

prolonged high-temperature exposure.

produced as shown in **Figure 11**.

or copper, the solidification range is determined primarily by the secondary alloying elements. Standard systems for melting, degassing, and alloy cleaning of cast alloys can be used without modification for the conventional casting of

*Fifty nm alumina particles in a matrix of AlMg10Ce8 alloy. Large white particles are aluminum oxide formed*

At solidification rates typical of castings in Ce alloys that contain more than 7% Mg, a homogenization heat treatment can be used to improve mechanical properties [17]. This treatment reduces the size and volume fraction of magnesium pools that can segregate in high magnesium alloys. The amount of cerium does not affect the segregation behavior. The alloys have been cast successfully in most traditional casting processes, such as sand, permanent mold, low pressure permanent, and die casting. **Figure 10** shows a cylinder head poured as a gravity casting showing the

Mechanical properties for the ternary Al-Ce-Mg system have been studied at both room and elevated temperatures (**Table 2**). The room temperature properties can be improved by both homogenization and hot isostatic pressing. One of the key attributes in the Al-Ce-Mg system is the recovery of mechanical properties at room temperature when exposed to elevated temperatures for prolonged periods of time. This alloy system does not contain any precipitates that become unstable after

Extrusions have been produced for applications where improved high-temperature performance or resistance to corrosion is desired. In these alloys, extrusion improves the properties through a combination of work hardening and alignment of the intermetallic. Extrusions have been produced at 300°C billet temperature and at extrusion ratios of 5.75–1 and 52–1 from an Al10Mg8Ce alloy. A comparison of average permanent mold properties to extruded properties is shown in **Table 3**. As the extrusion ratio increases, tensile strength remains constant, with the elongation increasing and yield strength decreasing. The mechanical properties can be affected by the starting microstructure of the billet. Structural extrusions have also been

**64**

*Air cooled cylinder head poured from Al-Ce binary alloy.*

**Table 2.**

*Room and elevated temperature properties of Al-10Mg-8Ce compared to common piston alloys.*

**Table 3.**

*Comparison of extruded data at different extrusion ratios with cast Al10Mg8Ce.*

**Figure 11.** *Structural extrusion produced for the marine industry.*

The alloy system has been used for both the direct write and powder bed fusion. Manca [18] has reported high mechanical properties of Al-3Ce-7Cu in both hightemperature tension and compression testing via selective laser melting. Fine eutectic phases of Al11Ce3 and Al6.5CeCu6.5 were found in the microstructure. High hardness values were noted after annealing at 400°C due to the precipitation of nanosized particles. Kessler [19] used induction heated Al-Ce wire to take advantage of the inherent rheology of molten Al-Ce and the high enthalpy of fusion for the reactive Ce-containing intermetallic. This intermetallic phase enhances the surface energy and stabilizes the extruded filament, imparting shape stability and facilitating layer-to-layer joining.


2.8.2. Sample Preparation Protocol

First, the specimens were cut into 4 × 4 mm pieces, and transferred into fixative at pH 7.2 in a 7 mL glass vial with attached lids and stand overnight at 4 ◦C. The next day, specimens were washed in 0.1 M phosphate buffer (3 times, 20 min each), and stored at 4 ◦C. Furthermore, 1 mL of buffered 1% osmium tetroxide was then added to each vial, and mixed for 1 h at room temperature on a Rota mixer. After that, the osmium tetroxide was removed and samples were washed three times in distilled water (for 2 min each). The samples were dehydrated through a series of ethanol washes. The next day, the specimens were washed again (twice) with 100% ethanol. The final flower sample was kept inside a desiccator for four days to allow gradual drying.

#### **3. Results and Discussion**

#### *3.1. EO Extraction by Hydrodistillation*

EO physical characteristics: The flowers' EO has a yellowish color with waxy nature, and has a characteristic floral odor similar to the fresh flowers.


**3.1 The feedback mechanism between saline farmland ecosystem and groundwater**

Traditional soil hydrology mainly pays attention to the influence of soil characteristics on non-biological processes such as water and solute transport. In contrast, agricultural hydrology focuses on the occurrence of various hydrological phenomena in agricultural measures and agricultural engineering and their intrinsic relationship, starting with the influence of water on biological processes such as crop growth and development. Studying the Earth's critical zone expands the research scope of farmland ecosystem and groundwater hydrological process and strengthens the critical role of soil physical process in multi-scale mass transport and cycle at land surface systems such as soil profile, slope, and basin [14]. In recent years, more and more studies have attempted to establish the relationship between shallow groundwater and vegetation physiology and weathering processes, to identify the critical groundwater table. At the same time, there is still a lack of mathematical expression and field validation for this relationship [10]. Zipper et al. [4] found that shallow groundwater table, root length density distribution, and root water compensation effects (i.e., plants adapt to drought conditions by absorbing more water from less-stressed parts of the root to compensate for root water uptake in areas where stress is more serious; [15]) had a significant impact on transpiration and NPP, emphasizing the importance of incorporating root compensatory water absorption equations into model studies.

## **3.2 GSPAC system water-salt coupling transport model**

At present, many mechanism models of the water-salt coupling transport process of GSPAC systems (e.g., HYDRUS, RZWQM, EPIC, SVAT, SHAW, etc. [16]) have been established, in which HYDRUS models are widely used [17]. Especially based on the concepts of mobile and immobile water bodies, HYDRUS introduce dual-porosity models that simulate large pore flows and preferential flows. These characteristic hydrological parameters and solute reactions are combined to simulate physical equilibrium and chemical nonequilibrium solute transport (e.g., tworegion models, two-site models, etc.), which provides convenience for the simulation of water-salt migration models under complex soil profile conditions (such as clay layer, gravel, large pores) with more regional influence factors (e.g., groundwater, irrigation water) [18–20]. However, the current model of the water-salt transport mechanism is limited within the unsaturated soil area, but it is insufficient in the saturated-unsaturated area, and the influence of groundwater on plant function has not been clarified. In turn, many crop models are good at simulating crop growth processes (e.g., RZWQM, WOFEST, DSSAT, AquaCrop, etc. [21]), but the expression of soil hydrological processes is insufficient, especially the lack of simulating groundwater dynamics. Many methods have been used to couple hydrological and crop models in recent years, for example, HYDRUS-1D and crop model AgroIBIS coupling AgroIBIS-VSF models [12].

*The "Groundwater Benefit Zone", Proposals, Contributions and New Scientific Issues DOI: http://dx.doi.org/10.5772/intechopen.100299*

**Figure 3.** *Diagram of MAGI Model Research Framework (quoted from [22]).*

It is worth mentioning that although some crop models can simulate the relationship between groundwater and vegetation in some ways, there is a very lack of mechanism models like the AgroIBIS-VSF model that can describe the effects of groundwater dynamics on soil temperature, oxygen, and leaf microclimate conditions. Furthermore, Zipper et al. [22] combined the latest version of the AgroIBIS-VSF model (i.e., the coupling of AgroIBIS and HYDRUS-1D) with the MODFLOW model to create a new model framework, MODFLOW-AgroIBIS (MAGI). The new coupled model simulates vegetation growth dynamics based on environmental conditions and quantifies the movement of water and energy in the GSPAC system (**Figure 3**). This coupling approach provides three widely-used model benefits for the MAGI model (①AgroIBIS [23], ②HYDRUS-1D [24] and ③MODFLOW-2005 [25]. However, most of the work related to the current MAGI model is carried out in non-saline conditions, while in areas with high groundwater salinity, the salt environment in the root zone of the crop will affect the potential of groundwater utilization and limit the applicability of the model framework. It means that the effects of salt must be taken into account when use models that need to be updated to calculate groundwater yield subsidies in saline agriculture (**Figure 3**).


*Article* **Research on the Adaptability of High-Performance Film for Full Recycling to the Curl-Up Film Collecting Method**

**Jie Liu 1, Xuanfeng Liu 2, Yongxin Jiang 2, Xin Zhou 2, Li Zhang 2 and Xuenong Wang 1,\***

**Abstract:** Given the problem of the low tensile performance of the plastic film used in China, which brings about difficulties in curl-up film collecting, in this study, a contrast test was carried out on the tensile property of high-performance film for full recycling and the ordinary polyethylene film (PE film) that is used extensively in China. Test results showed that, within the service period, the elongation at break and tensile yield stress of the high-performance film were higher than those of ordinary polyethylene film, and, within the film-laying period of 0~30 days, the reduction scale of the elongation at break and tensile yield stress was higher than that within the film-laying period of 30~180 days. In this study, in order to obtain the lowest tensile performance of the film by curl-up film collecting, the operation principles of the curl-up film collectors were analyzed. The test on the force of curling up the film in the process of overcoming the force between the film and soil was analyzed. Test and analysis results showed that, for different sampling positions, film pick-up angles, and film types, the tensile stress on the film while pulling it up was within a range of 15.97~21.86 MPa. In order to verify the curling up effect of differently structured film collectors on different types of film with different thicknesses, a field test on film curl-up collecting was designed. A contrast test was carried out on two types of curl-up film collectors, 1JRM-2000 and 11SM-1.2, and the test results showed that the film recycling rate and working performance on the film laid in the same year by the film collector with a fixed film pick-up angle were higher than those for varying film pick-up angles. The curl-up film collector fixed with an automatic film-guiding mechanism is not affected by the velocity difference between the linear velocity of the film curl-up mechanism and the advancing velocity of the machine. The film recycling rate and working performance on the film laid in the same year by the 11SM-1.2 curl-up film collector can meet the operational requirements for collecting high-performance film with thicknesses of 0.008 mm and 0.01 mm. This research can provide a reference for simplifying the structure of residual plastic film collectors, increasing the film recycling rate, and reducing the cost.

**Keywords:** high-performance film for full recycling; film recycling; field experiment; film recycling rate


KM and FCM algorithm

1.Select k vectors randomly from the dataset as initial cluster centers μj (j = 1, …, k). Set the current iteration t = 0.

2.KM-Step: assign each vector Xi to its closest cluster center using Eq. (1).

3.FCM-Step: set t = t + 1.

4.For each cluster Cj, compute the center μj using Eq. (3)

5.Compute the new membership matrix Uð Þt k X N using Eq. (4)

6.Assign data objects to clusters using the membership matrix.

7.Compute Percentage change using Eq. (2).

8.Stop the process if Percentage change < α. Otherwise, set t = t + 1.

9.KM-Step: For each cluster Cj, compute new center μj using Eq. (3).

10.Assign each vector Xi to its closest cluster center using Eq. (1).

11.Compute Percentage change using Eq. (2).

12.Stop the process if Percentage change < α. Otherwise, go to step 3.

For all the algorithms, i.e., KM, FCM, KMFCM, KMandFCM, the same termination condition, Eq. (2), is used.

## 5. Performance evaluation measures

For performance evaluation of algorithms, CPU time in seconds, sum of squared error [12] and clustering fitness [43] are taken into consideration and are calculated for all the algorithms.

#### 5.1 Sum of squared errors

The objective of clustering is to minimize the within-cluster sum of squared error (SSE). The lesser the SSE, the better the goodness of fit is. The sum of squared error [12] for the results of each clustering algorithm is computed using the Eq. (5)

Segmenting Images Using Hybridization of K-Means and Fuzzy C-Means Algorithms DOI: http://dx.doi.org/10.5772/intechopen.86374

$$\text{SSE} = \sum\_{j=1}^{k} \sum\_{X\_i \in C\_j} \left( X\_i - \mu\_j \right)^2 \tag{5}$$

Here, Xi is the ith data object in the dataset, μj (j = 1, …, k) is the center of the cluster Cj, and k is the number of clusters.

#### 5.2 Clustering fitness

The main objective of any clustering algorithm is to generate clusters with higher intra-cluster similarity and lower inter-cluster similarity. So, it is also important to consider inter-cluster similarity while evaluating the clustering performance. In the present work, clustering fitness is also considered as a performance criterion, which requires the calculation of both intra-cluster similarity and inter-cluster similarity. The computation of clustering fitness also requires the experiential knowledge, λ. The computation of clustering fitness results in higher value when the inter-cluster similarity is low and results in lower value for when the inter-cluster similarity is high. Also that to make the computation of clustering fitness unbiased, the value of λ is taken as 0.5 [43].

(a) Intra-cluster similarity for the cluster Cj: it can be quantified via a function of the reciprocals of intra-cluster radii within each of the resulting clusters. The intra-cluster similarity [43] of a cluster Cj (1 = j = k), denoted as Stra(Cj ), is defined in Eq. (6)

$$S\_{\rm tra}(\mathbf{C}\_{j}) = \frac{\mathbf{1} + n}{\mathbf{1} + \sum\_{1}^{n} dist(I\_{l}, Centroid)} \tag{6}$$

Here, n is the number of items in cluster Cj, Ij (1 = j = n) is the jth item in cluster Cj, and dist(Ij, Centroid) calculates the distance between Ij and the centroid of Cj, which is the intra-cluster radius of Cj. To smooth the value of Stra(Cj) and allow for possible singleton clusters, 1 is added to the denominator and numerator.

(b) Intra-cluster similarity for one clustering result C: it is denoted as Stra(C). It is defined in Eq. (7), [43]

$$\mathbf{S}\_{\text{tra}}(\mathbf{C}) = \frac{\sum\_{1}^{k} \mathbf{S}\_{\text{tra}}(\mathbf{C}\_{j})}{k} \tag{7}$$

Here, k is the number of resulting clusters in C and Stra(Cj) is the intra-cluster similarity for the cluster Cj.

(c) Inter-cluster similarity: it can be quantified via a function of the reciprocals of inter-cluster radii of the clustering centroids. The inter-cluster similarity [43] for one of the possible clustering results C, denoted as Ster(Cj ), is defined as Eq. (8)

$$\mathcal{S}\_{ter}(\mathcal{C}) = \frac{1+k}{1 + \sum\_{1}^{k} \text{dist}\left(\text{Centroid}\_{j}, \text{Centroid}^{2}\right)} \tag{8}$$

Here, k is the number of resulting clusters in C,1= j = k, Centroidj is the centroid of the jth cluster in C, Centroid2 is the centroid of all centroids of clusters in C. We compute inter-cluster radius of Centroidj by calculating dist(Centroidj, Centroid2 ), which is distance between Centroidj, and Centroid2 . To smooth the value of Ster(C)

and allow for possible all-inclusive clustering result, 1 is added to the denominator and the numerator.

(d) Clustering fitness: the clustering fitness [43] for one of the possible clustering results C, denoted as CF, is defined as Eq. (9)

$$\text{CF} = \lambda \times \text{S}\_{\text{tru}}(\text{C}) + \frac{1 - \lambda}{\text{S}\_{\text{tr}}(\text{C})} \tag{9}$$

Here, λ (0 < λ < 1) is an experiential weight, Stra(C) is the intra-cluster similarity for the clustering result C and Ster(C) is the inter-cluster similarity for the clustering result C. To avoid biasedness in our experiments, λ is assumed to be 0.5.


Preface

As a physician working in the Department of Gastroenterology, I am very pleased to cooperate with IntechOpen to launch a book about the digestive system in January 2019. Through persistent efforts, a total of 9 chapters, which are authored by worldwide experts in the field of liver diseases, are included in this book entitled as "*Digestive System - Recent Advances*". The book is divided into 3 major sections: gastrointestinal duct, liver, and biliary system. In more detail, the book covers peptic ulcers, mid-gastrointestinal bleeding, gastrointestinal manifestations of IgA vasculitis, biomechanics of intestinal contractions, gallbladder carcinoma, ERCP for cholecysto-choledocholithiasis, and cystic artery variations and associated vascular complications in laparoscopic cholecystectomy and the evaluation of serum sodium change after terlipressin in cirrhosis. The knowledge presented in the book should be valuable for family physicians, internists, gastroenterologists, and hepatologists who are interested in digestive diseases to guide the clinical practice and management. This book should be also useful for patients and their relatives to better understand the digestive system.

I am deeply indebted to the assistance from IntechOpen staff, including Andrea Koric (Commissioning Editor) and Lada Bozic (Author Service Manager). Also, I greatly appreciate the support from all chapter authors. Finally, I wish to dedicate this book to my wife Jun Liu.

> **Dr. Xingshun Qi** Department of Gastroenterology, General Hospital of Northern Theater Command, China

I am extremely pleased to work with IntechOpen to launch this book on the digestive system, with the section on the biliary system under my supervision. The chapters cover the variations, complications, and latest modifications in various topics of the biliary system. Some of the topics such as gallbladder carcinoma, ERCP for cholecysto-choledocholithiasis, and cystic artery variations and associated vascular complications in laparoscopic cholecystectomy, have been described keeping in mind the current practice and the recent advances in the field. The knowledge presented in this book should be valuable for young surgeons as a guide for the clinical practice and management.

As an editor I have tried to ensure that the descriptions and techniques illustrated are representative of contemporary practice while keeping the information current and simple.

**II**

**Chapter 7 103**

**Chapter 8 113**

**Chapter 9 123**

Gall Bladder Carcinoma: Clinical Presentations and Different Modalities of

Intraoperative ERCP for Management of Gallbladder and Common Bile

Cystic Artery Variations and Associated Vascular Complications in

*by Pankaj Prasoon, Tomohiro Katada, Kohei Miura, Yuki Hirose, Jun Sakata*

*by Wala Ben Kridis, Nabil Toumi, Jamel Daoud, Afef Khanfir and Mounir Frikha*

Treatment

Duct Stones

*by Ahmed Abdelraouf Elgeidie*

Laparoscopic Cholecystectomy

*and Toshifumi Wakai*

I would like to thank God Almighty for giving me the vision and opportunity to be part of this book. I deeply appreciate the IntechOpen staff, including Andrea Koric (Commissioning Editor) and Lada Bozic (Author Service Manager) for their continuous support. I extend my thanks to all the authors for their time and effort. My sincere gratitude to Dr. Santhosh John Abraham (Professor and HOD Gen Surgery, Past President – Associations of Surgeons of India, Dr. Vimal Iype (Head of Vascular Surgery), my colleagues Dr. Arunesh Dubey, Dr.Nidhin, and Dr. Sooraj Sankar for their timeless help and support. Finally I would like to thank my parents, and my wife for the enormous support throughout the years.

> **Dr. Sam Koruth** Lourdes Hopital, Kerala, India

> > Section 1

Gastrointestinal Duct

1

Section 1


**4.2 Brain functions in swallowing**

The sensory nerves report perceptions of pressure, texture, taste, and temperature, and these are transmitted by these afferent nerves to the brain. The primary source of these stimuli is from the nerves in the lips and then, in turn, the tongue, soft palate, and pharynx (**Figure 6)** [5, 29]. The (CN V) Trigeminus is the thickest and fastest of the efferent nerves, and thus the signals from the lips are the first to reach the brain stem. It is therefore a mistake to concentrate on therapies for the tongue, soft palate, and pharynx that omit the importance of the lips.

The five cranial motor nerves that are important for swallowing are CN V Trigeminus, CN VII Facialis, CN IX Glossopharyngeus, CN X, Vagus, and CN XII Hypoglossus*.* The first four are both sensory (afferent), and motor (efferent) nerve pathways; which send information both to and from the brain - the sensory-motoric reflex arc.

**Figure 6.** *The cranial nerves and reflex points of the oral cavity.*