FeSiB非晶薄带激光焊接头组织及晶化行为

Microstructure and crystallization behaviour of laser welding FeSiB amorphous ribbon joint

采用脉冲激光焊接技术成功实现FeSiB非晶带材的搭接,并通过热处理方法分析接头晶化行为。利用扫描电子显微镜SEM、X射线衍射仪XRD、差示扫描热仪DSC和透射电镜TEM等研究不同功率对激光焊缝成形、组织特征及晶化行为的影响。结果表明:当功率低于4.8 W时,焊缝表面粗糙、熔宽小;当功率高于9.6 W时,焊缝存在微裂纹;当功率为7.2W时,焊缝成形良好,未见焊接缺陷。随着功率的增加,接头抗拉强度先升高后降低,最高拉伸强度为410 MPa,断裂方式为解理断裂;接头组织主要由非晶相、树枝晶、白色颗粒状的结晶相组成;接头晶化过程中先析出α-Fe(Si)相,再析出Fe_2B相。

FeSiB amorphous ribbons were successfully pulse laser lap welded, and the crystallization behavior in the weld was investigated in heat treatment. The effects of pulse power on weld formation, microstructure and tensile properties were studied, and the crystallization process of amorphous ribbon was analyzed by testing technologies. The results show that the weld surface is rough and the weld width is narrow when the power is below 4.8 W. However, some microcracks are formed on the weld surface with power exceeding 9.6 W. When the power is 7.2 W, the weld quality is best without welding defects. With the increase of pulse power, the tensile strength of the joint first increases and then decreases, the highest tensile strength reaches to 410 MPa. The failure of the joints is a cleavage fracture. Moreover, the microstructure in the joint is mainly composed of amorphous phase, dendrites, crystalline phase with white particle shape. An obvious crystallization process occurs during welding, where the α-Fe(Si) phase is firstly precipitated, and then the Fe_2B phase is formed.