Twinning-induced plasticity (TWIP) steels have become important materials in industry owing to the good combination of strength and ductility and high strain hardening rate. The excellent mechanical properties are highly related to the glide of dislocation and deformation twinning. However, the cross-slip behavior of the extended dislocation and the mechanism of deformation twinning are still controversial. Here, the partial dislocation motion and austenite twinning of a high-Mn steel at the early stage of deformation were investigated using in-situ tensile transmission electron microscope (TEM) technique. Results show that a large number of plane glide and cross-slip of extended dislocations can occur at the early stage of deformation. Extended dislocation nodes can be formed as a result of the reaction between adjacent extended dislocations on the same glide plane. In-situ tensile TEM experiments confirm two cross-slip models of partial dislocation: (1) the Friedel-Escaig model, cross-slip based on constriction of extend dislocation and re-dissociation; (2) the Fleischer model, cross-slip involving Lomer-Cottrell dislocation. Based on experimental results and energy calculations, it can be confirmed that the formation mechanism of austenite primary deformation twin induced by partial dislocations is different from that of secondary deformation twin. Grain boundary emits partial dislocation into the grain to form stable stacking fault which induces austenite primary deformation twin. The formation of secondary deformation twin is related to cross-slip of extended dislocation. Only the cross-slip of an extended dislocation containing a 90° partial dislocation can induce the formation of secondary deformation twin by introducing the Frank partial dislocation.

中文翻译：

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高锰 TWIP 钢中扩展位错的交叉滑移和二次变形孪晶

孪生诱导塑性（TWIP）钢由于强度和延展性的良好结合以及高应变硬化率而成为工业中的重要材料。优异的力学性能与位错的滑移和变形孪晶密切相关。然而，扩展位错的交叉滑移行为和变形孪晶的机制仍然存在争议。在这里，利用原位拉伸透射电子显微镜（TEM）技术研究了高锰钢在变形早期的部分位错运动和奥氏体孪晶。结果表明，变形初期会发生大量的扩展位错的平面滑移和交叉滑移。扩展位错节点可以由于同一滑移面上相邻扩展位错之间的反应而形成。原位拉伸TEM实验证实了两种部分位错的交叉滑移模型：（1）Friedel-Escaig模型，基于扩展位错收缩和再解离的交叉滑移； (2) Fleischer 模型，涉及 Lomer-Cottrell 位错的横向滑移。根据实验结果和能量计算，可以证实部分位错引起的奥氏体初次变形孪晶的形成机制与二次变形孪晶的形成机制不同。晶界向晶粒内发射部分位错，形成稳定的堆垛层错，诱发奥氏体初次变形孪晶。二次形变孪晶的形成与扩展位错的交叉滑移有关。只有包含90°部分位错的扩展位错的交叉滑移才能通过引入弗兰克部分位错来诱导二次形变孪晶的形成。