TWIP钢激光拼焊板的力学性能及微观组织分析

为评价TWIP钢的焊接性能,对1.2 mm厚的Fe-Mn-C系TWIP钢进行了激光拼焊实验,用线扫描分析了锰元素的分布,对拼焊板进行了拉伸试验,用扫描电镜观察了拉伸断口形貌,采用背散射电子分析技术分析了拉伸前后的组织变化及孪晶形成,测试了维氏硬度的分布曲线.实验结果表明:焊缝区未发生Mn元素的挥发,室温下为显著的柱状枝晶铸态组织;断裂发生在存在气孔等微小缺陷的焊缝区,拼焊板强度与母材接近,韧性显著降低;拉伸过程中有大量的形变孪晶形成,拉伸前后均为全奥氏体组织.

Mechanical properties and microstructure of laser welded TWIP steels

To evaluate the welding performance of TWIP steel, the results of laser welding of 1.2 mm Fe-Mn-C series TWIP steels were presented in this paper. Energy-dispersive X-ray spectrometry(EDX) was used to detect the effect of manganese segregation. Microhardness and tensile tests were performed to evaluate the mechanical properties of the joints. The fracture mechanism was observed by scanning electron microscopy(SEM). The twinning phenomena was assessed by electron back-scatter diffraction(EBSD) analyses. The results indicate that there is no manganese evaporation in the FZ area, it is dendritic structures at room temperature. Fracture all occurs in the FZ due to the welding defects such as voids, and the strength of the joint is similar to that of the base metal. However, the toughness is reduced remarkably. Twinning is the predominant deformation mechanism, the microstructure of welding joint are all austenite.