采用磁性测量、光学金相和强脉冲磁场,研究了Fe-21Ni-4Mn合金的磁场诱发马氏体相变。发现在M_s点以上,当施加的磁场高于某一临界值(临界磁场)时,便能诱发马氏体相交;临界磁场随温度的升高而增加,并与ΔT(T-M_s)成直线关系;脉冲磁场强烈地促进变温转变,抑制等温转变;磁场对Fe-21Ni-4Mn合金的马氏体相变作用主要是Zeeman效应,求得在M_s点变温的熵变ΔS_(M_S)~(1t)为·13J/mol·K·同时发现磁场诱发的马氏体形貌为板条伏、片状和蝶状,其形成量随施加的最大磁场强度成线性增加。
Magnetic field-induced martensitic transformation in an Fe-2lNi-4Mn(wt-%) alloy with isothermal and athermal martensite transformation kinetics hasbeen studied by magnetization measurement and optical microscopy, applying apulsed ultrahigh magnetic field. The following results were found: a magnetic fieldhigher than a critical one is needed to induce the martensitic transformation aboveM_s. The critical magnetic field increases with increasing temperature, and whenplotted against the temporature difference from M_s, it lies on a straight line notpassing through the origin. This result and thermodynamical analysis suggest thatpulsed magnetic field strongly promotes the athermal martensitic transformation andrestrains tht isothermal one. The influence of magnetic field on martensitic trans-formation in the present Fe-Ni-Mn alloy is mainly due to Zeeman effect. Theentropy change for athermal transformation at M_s, S_Ms~at is obtained to be 4.13J/mol.K. The amount of magnetic field-induced martensites increases linearly withthe maximum strength of pulsed magnetic field. Lath, plate and butterfly martensi-tes are formed under magnetic field.
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