Effect of heat treatment on microstructure and mechanical properties of a graded structural material

A novel graded structural material (GSM) of Ti-6Al-4V/Ti-6.5Al-3.5Mo-1.5Zr-0.3Si had been designed by authors and successfully fabricated by laser melting deposition (LMD) manufacturing technology. The effects of solution treatment and aging and thermal exposure on microstructure and mechanical properties of the GSM were studied. Microstructural evolution, chemical composition in gradient zone and tensile fracture morphologies were examined by OM, SEM and EPMA equipped with WDS. Results indicate that microstructure of the GSM is coarsened obviously and its tensile strength has decreased slightly after solution treatment and aging. Thermal exposure treatment does not have obvious effects either on the microstructure or the tensile strength of the GSM experienced solution treatment and aging. Moreover, it is worth noting that the GSM displays a better tensile ductility than those of Ti-6Al-4V or Ti-6.5Al-3.5Mo-1.5Zr-0.3Si in transversal direction. It is contributed to the existence of the interface between Ti-6Al-4V and Ti-6.5Al-3.5Mo-1.5Zr-0.3Si which delays the development of premature local necking. The GSM exhibits good room temperature tensile properties and thermal stability.