The grain orientation dependence of the deformation-induced forward fcc→hcp and reverse hcp→fcc martensite transformation of a FeMnSi-based shape memory alloy was studied by in situ neutron diffraction during cyclic loading. A deformation-induced fcc→hcp transformation is observed during tensile straining to +2%. The hcp martensite phase that forms under tension partially reverts to fcc austenite upon subsequent compression from +2% → −2% for the {220}, {331} and {111} grain families aligned with respect to the loading direction but not for the {200} grain family. The martensite formation and the reversion of the individual grains can be explained by considering grain orientation dependent Schmid factors of the {111}<112> slip system underlying the fcc to hcp transformation. While for post-yield elastically compliant grains the Schmid factor of the leading partial dislocation is larger than that of the trailing partial dislocation, the opposite is true for post-yield elastically stiff grains. The former grains show a phase reversion, i.e. hcp→fcc upon compression, the latter grains do not transform back to fcc. EBSD characterization confirms the phase reversion for a <541> orientated grain by the disappearance of hcp bands. Martensite bands, which have not reverted to austenite during compression, showed a thickening. The thickening of existing bands during compression is associated with the activation of a second slip system.

通过原位研究了FeMnSi基形状记忆合金的形变诱导的正向fcc→hcp和反向hcp→fcc马氏体相变的晶粒取向依赖性。循环加载过程中的中子衍射。在拉伸应变至+ 2％期间观察到了变形引起的fcc→hcp转变。在受压方向上{220}，{331}和{111}晶粒系列的压缩后，在张力下形成的hcp马氏体相从+ 2％→-2％压缩后部分回复为fcc奥氏体，但不压缩。 {200}谷物家族。马氏体的形成和单个晶粒的回复可以通过考虑基于{cc}到hcp转变的{111} <112>滑移系统的晶粒取向依赖性Schmid因子来解释。对于屈服后弹性顺应晶粒，前导部分位错的施密特因子大于尾随部分位错的施密特因子，而屈服后弹性坚硬的晶粒则相反。前一个晶粒显示出相变，即压缩时hcp→fcc，后一个晶粒不转换回fcc。EBSD表征通过hcp条带的消失证实了<541>取向晶粒的相变。在压缩过程中未还原为奥氏体的马氏体带显示出增厚。压缩期间现有带的增厚与第二滑动系统的激活相关。