In this work, electron backscatter diffraction and digital image correlation techniques were employed to study the microstructure and microstructure-property relationship in friction-stir welded TRIP steel. It was found that the thermal effect of the welding process led to material softening in the heat-affected zone and promoted martensite transformation in the stir zone. These microstructural changes provided rapid strain localization during subsequent transverse tensile tests and thus resulted in premature failure of the welds.

Material softening in the heat-affected zone was deduced to be a combined result of dissolution and spheroidisation of retained austenite as well as recovery in bainitic ferrite. The stir zone martensite was characterized by significant orientation spread and therefore its orientation relationship with austenite essentially deviated from the ideal Kurdjumov-Sachs relation. Moreover, the martensite transformation was found to be influenced by variant selection.

在这项工作中，电子反向散射衍射和数字图像相关技术被用来研究摩擦搅拌焊接的TRIP钢的组织和性能之间的关系。发现焊接过程的热效应导致热影响区的材料软化并促进搅拌区的马氏体转变。这些微观结构的变化在随后的横向拉伸试验中提供了快速的应变局部化，因此导致了焊缝的过早失效。

推测热影响区的材料软化是残余奥氏体溶解和球化以及贝氏体铁素体恢复的综合结果。搅拌区马氏体的特征在于明显的取向扩展，因此其与奥氏体的取向关系实质上偏离了理想的Kurdjumov-Sachs关系。此外，发现马氏体相变受变体选择的影响。