Study On Magnetic-Field-Induced Strain Of Mn-Cu Alloy

In this paper, the effects of Mn content, aging, and addtion of Fe element on the microstructure and Magnetic-field-induced strain (MFIS) in Mn-Cu alloys are investigated by means of X-ray diffratction analyzer, photomicrograph, DSC, resistance strain gauge method. The results of the research show that the MFIS can be obtained in polycrystalline Mn-Cu alloys at room temperature and at the low magnetic field from 0 T to 0.9 T, which increase with magnetic field strength enhancing.After aging, Mn-rich and Cu-rich decomposed regions form in Mn55Cu45 alloy, and the f.c.c. (γ)→f.c.t. (γ') martensitic transformation occurs in the Mn-rich regions, at last the MFIS of alloy reaches its maximum value of 4.2×10-5. Mn100-xCux (x=10,20,30) alloys consist of y and y'phases after a long period of homogenization because theγ→γ'transformation occurs. The volume proportion ofγ' phase increases with the increase of Mn content, so that, the MFIS performance is improved. When the applied magnetic field strength decreases, the MFIS decreases. At room temperature, the MFIS in Mn90Cu10 sample reaches the value of 9.1×10-5 in the applied magnetic field of 0.9 T.Theγ→γ' transformation occurs in Mn7oCu3o alloy during the aging process. The volume proportion ofγ' phase increases with the increase of aging time, so that the samples possess much larger MFIS which can reach 9.3×10-5. But when aging time exceeds 12 hours, there are a large number of a phase precipitated, which degrading the MFIS of alloy. Theγ→γ' transformation also exists in Mn8oCu20-xFex (x=0,2,4) alloys, and there are some of detached a phase and s phase. Under the magnetic field, Mn80Cu20-xFex alloys possess much larger MFIS with the increase of Fe content, which can close to the level of Mn90Cu10 alloy.