通过扫描电子显微镜(SEM)、电子背散射分析(EBSD)，研究了TRIP590 钢激光焊接接头的界面微观结构和形成机理。SEM 分析表明，焊接接头焊缝区组织为马氏体组织，热影响区组织主要是贝氏体和铁素体，离焊缝位置越近，马氏体量越多。EBSD 分析表明，母材区的晶粒分布均匀，都是大角度晶界，没有明显的择优取向。热影响区晶粒大小不均，贝氏体有相同或相近的取向。焊缝区板条尺寸最为粗大，有明显的织构。残余奥氏体弥散分布在晶粒内部或晶界，焊缝和热影响区晶界取向差都是1°~5°之间的小角度晶界，大量的小角度晶界导致焊缝与热影响区的塑性要小于母材。

Scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) are used to study the interface microstructure and formation mechanism of laser welding joints of TRIP590 steel. Analyzes of SEM indicate that the microstructure of weld zone is matensite, and the microstructure of heat affected zone (HAZ) are bainite and ferrite. The closer of the weld, the more martensite HAZ has. The results of EBSD analysis show that there is no obvious preferred orientation and uniform sizes of grains in base zone, and most of grain boundaries are high angle grain boundaries. The grain size of HAZ is unequal and the bainite has the same or similar orientation. The laths size of weld zone is coarser and it has obvious texture. Retained austenite is dispersed in grains and grain boundaries. The orientation difference of grain boundary of weld and HAZ is low-angle boundary which is between 1°~5°. A large amount of low-angle boundary would lead to the plasticity loss of weld and HAZ compared with base metal.