Microstructural evolution and mechanical properties of laser melting deposited Ti-6.5Al-3.5Mo-1.5Zr-0.3Si titanium alloy

A rectangular plate of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si titanium alloy was fabricated by laser melting deposition (LMD) technology. Macrostructure and microstructure were characterized by optical microscope (OM) and scanning electron microscope (SEM). Room temperature tensile properties were evaluated. Results indicate that the macro-morphology is dominated by large columnar grains traversing multiple deposited layers. Two kinds of bands, named the wide bands and the narrow bands, are observed. The wide band consists of crab-like α lath and Widmanstätten α colony. The narrow band consists of α lath and transformed β. The formation mechanism of the two bands was explored. The influence of heat effect caused by subsequent deposition layers on microstructural evolution during deposition process was discussed. The room temperature tensile test demonstrates that the strength of laser deposited Ti-6.5Al-3.5Mo-1.5Zr-0.3Si is comparable to that of wrought bars.