The fatigue life cycles are determined to be 390,000–398,000 times under tensile load of 450 MPa and 90,000–96,000 times under the load of 500 MPa with magnetic field, which are higher than those of 330,000–350,000 times under tensile load of 450 MPa and 85,000–89,000 times under the load of 500 MPa without magnetic field.