Abstract
In the present investigation, welding of 1 mm thick Ti-6Al-4V sheet has been done by Pulsed Wave (PW) Nd-YAG laser with a variation of laser power from 100 to 400 W and welding speed from 4 to 6 mm s^-1. The microstructure and microhardness of the fusion zone indicate that the finely serrated and regular plate-shaped microstructures and the resultant hardness in the welds are the key factors behind the enhanced tensile strength of all joints. The weld bead size increases with decreasing welding speed and vice versa. The hardness increases around the heat affected zone as compared to that of the parent metal, and it is the maximum at the centre of the welded region. In the investigation, the tensile strength of specimen with different process parameters has been found to be approximately equal to the tensile strength of the parent metal. In XRD analysis, the weld zone has been found to consist of 78 % α and 22 % β peaks where two β-titanium peaks (bcc) 100 occur at 39.5110° and 56.9120°.

Key words
microstructure, microhardness, pulsed wave laser, tensile strength

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