NiTiNb箔片激光焊接工艺及其接头的组织与性能

Laser welding process of NiTiNb foil and microstructure and properties of welding joint

采用Nd:YAG激光器实现200μm厚Ni47Ti44Nb9形状记忆合金箔片的焊接,并对激光工艺参数进行了正交试验。采用光学显微镜观察接头的显微组织,用精密拉伸仪测试了接头强度,并用精密硬度计测试了接头的显微硬度。结果表明:200μm厚Ni47Ti44Nb9形状记忆合金对接的最优激光工艺参数是平均功率为16.8 W,脉宽为4.4 ms,频率为4.5 Hz,此时,接头的抗拉强度为880 MPa,达到母材强度的95%。水平面呈均匀的鱼鳞纹状。横截面出现了分层现象,焊缝中心为超细等轴晶,热影响区为柱状组织。纵截面为等轴晶与NiTi-βNb伪共晶析出带交替分布,焊缝区的平均硬度大于母材的平均硬度。

The welding joint of Ni47Ti44Nb9 shape memory alloy with thickness of 200 μm was achieved by Nd：YAG laser, and the laser process parameters were investigated by orthogonal experiment. The welding joint microstructure was observed by optical microscopy, the strength of extension of the joint was tested by precision stretcher, and the micro-hardness of the welding joint was tested with the precision hardmeter. The results shows that the best laser parameters of jointing Ni47Ti44Nb9 shape memory alloy with thickness of 200 μm are that the average power is 16.8 W, the width of pulse is 4.5 ms and the frequency is 4.5Hz. At this time, the tensile strength is 880 MPa, reaching 95% strength of the base metal. The horizontal surfaces appear uniform scales striate. And there is a phenomenon of layering on the cross-section, the center of the welding joint is ultrafine axis crystal. The heat affected zone is the column structure. The longitudinal section is exchange distribution of equiaxed grains and pseudoeutectic of NiTi-βNb. The average hardness of the welding joint is greater than that of the base metal.