Characterization of microstructure and mechanical properties of laser melting deposited Ti–6.5Al–3.5Mo–1.5Zr–0.3Si titanium alloy

Abstract

A plate of Ti–6.5Al–3.5Mo–1.5Zr–0.3Si (TC11) titanium alloy is fabricated by laser melting deposition process. Grain morphology and microstructure characteristics and the formation mechanism have been systematically studied. It is shown that the three dimensional macrostructure is a specially alternately arrayed grain morphology of columnar grains and equiaxed grains. This structure is generated by the high temperature gradient in the overlap zone and relatively low temperature gradient in the body zone of the molten pool. Combining the results of the X-ray diffraction (XRD) and the solidification process, it can be inferred that a preferential orientation with the β〈001〉along the deposition direction exists in the as deposited TC11 plate. An ultrafine basket-weave microstructure within the columnar and equiaxed grains is formed due to the rapid solidification process. The lamellar α within the columnar grains is much uniform than that of the equiaxed grains. Room tensile test data have shown that the LMDed material was characteristic of high strength and low ductility compared with the conventional forged materials.