The nonmagnetic austenite steels are the jacket materials for low-temperature superconductors of fusion reactors. The present work provides evidences that austenites transform to magnetic martensite when deformation with a high-strain is imposed at 77 K and 4.2 K. The 4.2 K test is characterized by serrated yielding that is related to the specific motion of dislocations and phase transformations. The in-situ transmission electron microscope (TEM) observations in nanoscale reveal that austenites achieve deformation by twinning under low-strain conditions at deep cryogenic temperatures. The generations of twins, martensitic transformations, and serrated yielding are in order of increasing difficulty.

非磁性奥氏体钢是聚变反应堆低温超导体的外套材料。本工作提供的证据表明，当在77 K和4.2 K处施加高应变变形时，奥氏体会转变为磁性马氏体。4.2 K测试的特征是锯齿形屈服，这与位错和相变的特定运动有关。纳米级的原位透射电子显微镜（TEM）观察表明，奥氏体通过在深低温下在低应变条件下孪生实现变形。双胞胎的世代，马氏体相变和锯齿状屈服是按照难度增加的顺序进行的。