Defocusing Effects of Laser Beam on the Weldability of Powder Metallurgy Ti-Based Shape Memory Alloys

The influence of defocusing distance of the fiber laser welding on Ti-51at%Ni, Ti-28%atNb and Ti-30at%Ta shape memory alloys (SMAs) was investigated. These alloys were produced by powder metallurgy (P/M) and sintered by furnace and microwave processes. The experimental results showed that the furnace-sintered Ti-Ni welds have the maximum porosity density and the lowest weld quality. While, the microwave sintered alloys of Ti-Nb and Ti-Ta SMAs presented better weldability, even though porosities were still observed. Ti-Ta SMA showed the best welding quality compared with the other welded joints. It can be concluded that porosities play important role in the welding of powder metallurgy alloys and in order to achieve high-quality welds, the porosities should be minimized.