Effect of laser-welding on mechanical strength of Ti-6Al-7Nb alloy castings

Objectives: To investigate the mechanical properties in term of microhardness of Ti-6Al-7Nb alloy and commercially pure titanium (cp Ti) castings after being laser-welded.

Methods: Six specimens of each alloy casting were cut in half and laser-welded with Nd/YAG laser-welding machine at 260 V of laser voltage. Then all laser-welded cast specimens were embedded in acrylic resin and polished until the center of laser-welded area exposed. The hardness of welded and unwelded areas of all cast specimens was measured with microhardness tester and metallographic microstructures of welded area were investigated using optical microscope. The data was analyzed at 95% of significant level.

Results: The microhardness of laser welded areas was higher than that of unwelded areas for Ti-6Al-7Nb alloy castings (p<0.05) for both Ti-6Al-7Nb alloy and cp Ti castings. Moreover, the microhardness at laser welded area of Ti-6Al-7Nb alloy was significantly higher than that of cp Ti (p<0.05).

Conclusion: The mechanical strength in term of microhardness of Ti-6Al-7Nb alloy and cp Ti increased after laser welding due to microstructural changes.