Context: In 1906, precipitation hardening alloys were discovered by Alfred Wilm. Precipitation hardening alloys, such as certain alloys of aluminium, titanium, and copper, are heat-treatable alloys that soften when quenched (cooled quickly), and then harden over time. After quenching a ternary alloy of aluminium, copper, and magnesium, Wilm discovered that the alloy increased in hardness when left to age at room temperature. Although an explanation for the phenomenon was not provided until 1919, duralumin was one of the first "age hardening" alloys to be used, and was soon followed by many others. Because they often exhibit a combination of high strength and low weight, these alloys became widely used in many forms of industry, including the construction of modern aircraft.

Question: Who discovered precipitation hardening alloys?
Answer: Alfred Wilm

Question: When were precipitation hardening alloys discovered?
Answer: 1906

Question: What happens to precipitation hardening alloys after they quenched?
Answer: harden over time

Question: One of the first "age hardening" alloys used were called?
Answer: duralumin

Question: What was used in the construction of modern aircraft?
Answer: duralumin

Question: What is done to make precipitation hardening alloys hardened immediately?
Answer: Unanswerable

Question: What term refers to cooling over time?
Answer: Unanswerable

Question: Who discovered precipitation hardening alloys in 1919?
Answer: Unanswerable

Question: What phenomenon was explained in 1906?
Answer: Unanswerable

Question: What was used in the construction of early aircraft's?
Answer: Unanswerable