Influence of pulsed Nd:YAG laser welding power on the microstructures and nano creep behaviour of Ti5Al2.5Sn beads

Pulsed Nd:YAG laser beam welding was performed at five different power levels (360 W, 380 W, 400 W, 420 W and 440 W), and the relationship between microstructure and nano creep behaviour was investigated for Ti5Al2.5Sn alloy. Microstructural analysis indicated a reduction in grain size in fusion zone, with an increase in the average laser power. In the fusion zone (FZ) of all the beads, acicular alpha and alpha martensite were observed and confirmed by SEM analysis. Due to the formation of the alpha and alpha phases during welding, the microhardness and nanohardness in the FZ increased by similar to 71% and similar to 58%, respectively, above that of the base alloy. Nano creep analysis suggested diffusional creep as the deformation mechanism in all the beads, except the one performed at an average power of 440 W since its stress exponent was less than 2.