The effect of friction stir spot welding (FSSW) parameters on microstructure and mechanical properties of transformation-induced plasticity (TRIP) steel joints was investigated. The microstructure of the base metal and welding zone (stir zone, thermomechanically affected zone, and heat-affected zone) was examined using OM, SEM, EBSD, and XRD. The results of fractography of joints show that the microstructure and size of bonding ligament are the main parameters affected on the weld strength. The influence of FSSW parameters such as rotational speed, dwell time, and plunge depth on the strength of the TRIP steel joints was investigated using response surface methodology and considering bonding ligament of joints. The results of analysis of variance (ANOVA) show that the mathematical model was in good agreement with actual amounts of joints strength. Analysis of variance also determined that the plunge depth was a more effective parameter than other parameters. By optimization of the parameters, it was found that the maximum strength (9.42 kN) can be achieved by choosing of the rotational speed at 1218 rpm, dwell time at 1.65 s, and plunge depth at 0.19 mm.

研究了搅拌摩擦点焊（FSSW）参数对相变诱发塑性（TRIP）钢接头组织和力学性能的影响。使用OM，SEM，EBSD和XRD检查了贱金属和焊接区（搅拌区，热机械影响区和热影响区）的微观结构。接头的断口扫描结果表明，粘结韧带的组织和大小是影响焊接强度的主要参数。使用响应面方法并考虑了接头的粘结韧度，研究了FSSW参数（如转速，停留时间和切入深度）对TRIP钢接头强度的影响。方差分析（ANOVA）的结果表明，该数学模型与实际的接头强度值非常吻合。方差分析还确定，切入深度是比其他参数更有效的参数。通过优化参数，发现可以通过选择1218 rpm的转速，1.65 s的停留时间和0.19 mm的切入深度来实现最大强度（9.42 kN）。