Magnetostriction Of Antiferromagnetic Fe-Mn Alloys

Magnetostrictive materials are intelligent materials widely applied to actuators and sensors.Antiferromagnetic Fe-Mn alloys are ideally required to have large magnetostriction coefficients,excellent mechanic processability and relatively low cost,which makes it a new kind of magnetostrictive material.This thesis attempts to conduct a systemic study of the relationship between the composition of Fe-Mn alloy and its structure and magnetostriction, analyzing the influences of cold rolling on the magnetostriction of this alloy.Fe_1-xMn_x(x=0.30,0.35,0.40,0.50,0.55)alloys were prepared by intermediate frequency inductive melting in vacuum.Alloys were heated to 1000℃at 5℃/m,homogenization treatment for 24 hours and furnace cooled and quenched in ice water,respectively.Fe_0.50Mn_0.50 alloys were prepared by twin rollers vertical pressing with the rolling capacity d=0.50,0.70, 0.90.The alloys were heated to 600℃,stabilized for 1 hour,and recovered and recrystallized. In this thesis,the influences of different heat treatments and rolling techniques on the microstructure and magnetostriction of Fe-Mn alloys have been investigated.The results showed that:The microstructure and magnetostriction of Fe_1-xMn_x(0.30≤x≤0.55)alloys are flexible with Mn content.When x=0.30,0.35,0.40,γ+εdual phase was easily kept down and the alloy showed poor magnetostriction;when x increased to 0.50,theγ+εdual phase of alloys changed intoγsingle phase with excellent magnetostriction.In 1.9T magnetic field,the magnetostriction of annealed Fe_0.50Mn_0.50alloys increased to 873×10^-6.Seen from phase and magnetostriction,alloys ofγsingle phase gained higher value of magnetostriction.The internal stress of the annealed alloys increased,causing poorer magnetostriction ofγsingle phase Fe-Mn alloys.But compared with quenched alloys,equably annealed alloys showed better magnetostrictive properties.The Fe_0.50Mn_0.50alloys of large magnetostriction were cold rolled,and the <110> preferred orientation was captured,but the alloys still showed face-centered cubic structure. The magnetostriction of rolled Fe_0.50Mn_0.50alloys decreased.When the alloys(d=0.70)were heated to 600℃,recovered and recrystallized,the magnetostriction was greatly improved, reaching 2124×10^-6in 1.9T magnetic field.