预置填充稀土激光焊接对TiNi形状记忆合金微观组织及成分的影响

Effect of Laser Welding Preset Rare Earth on the Microstructure and Composition of the Joint of TiNi Shape Memory Alloy

采用Nd-YAG连续激光器对Ti-Ni50.9at%形状记忆合金进行焊缝预置填充材料激光焊接,预置填充材料是通过熔炼方法制备的添加稀土元素La、Ce的与母材同等原子比的TiNi合金。利用光学显微镜、SEM电镜、EDX及XRD研究了填充稀土的TiNi合金接头的组织及成分。结果表明,填充稀土焊缝与未填充稀土焊缝的宏观形貌无明显差别,稀土在整个焊缝接头处分布均匀,不存在宏观区域偏析现象,以细小白色的弥散颗粒相形式分布在晶界、亚晶界以及亚晶胞内部。与未填充稀土的焊缝相比,填充稀土的焊缝组织晶粒明显细化;晶界,特别是亚晶界淡化。可见预置填充稀土材料激光焊接改善了TiNi形状记忆合金焊缝的组织。

The laser welding preset rare earth for Ti-Ni50.9 at% shape memory alloy was conducted by using Nd-YAG continuous laser-welding machine, in which Ti-50.9at% Ni alloy was prepared by melting process. The microstructure and composition of the weld joint with rare earth were investigated through optical microscopy, scanning electron microscopy, energy spectrum analysis, X-ray diffraction analysis. The results show that the rare-earth element in the weld joint was uniformly distributed without segregated zone. Rare earth with white and fine dispersion grains was distributed in the grain boundary, sub-boundary and internal of sub-crystal cell. The macrostructure of the weld with rare earth is approximately identical to the weld without rare earth. Crystal grain in the weld with rare earth is refined, and the grain boundary, sub-boundary and the directionality of columned crystals are weakened. Adding rare earth elements can improve the strength and toughness of the welded joint of the TiNi alloy.