Influence of laser pulse on solidification of molten pool during laser welding of dissimilar Ti-based amorphous alloys

Abstract

Dissimilar Ti-based amorphous alloy sheets were butt welded by a pulsed laser and metallurgical joints were obtained. The β-Ti crystal grains in nanometre scale unevenly distribute on the amorphous background in the fusion zone. With the increase of laser pulse energy and pulse duration, the crystalline β-Ti grains grow up from spherical to dendritical profile, but the crystalline size reaches its maximum of about 1 µm, which is much smaller than the grains in base metal. The refinement of the grains in fusion zone results from the fast cooling speed during welding. The microhardness in the welded joints ranges from 470 to 525 HV. Average tensile strength of the welded joint is about 1510 MPa (86% of pure Ti-based amorphous alloy BM and 91% of β-Ti dendrite reinforced Ti-based amorphous alloy BM).