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A novel α+β titanium alloy with multi-alloying addition and low-cost is designed from Ti-6Al-4V. In order to maintain the same [Al] eq and [Mo] eq , the Mo and Zr were added into the alloy instead of V, and the nominal composition of this novel alloy is determined as Ti-6Al-2V-1.5Mo-0.5Zr-0.3Si with a spot of Si added. In this study, a plate of the novel alloy was manufactured by laser additive manufacturing (LAM). The macrostructure, microstructure, compositions, microhardness and room temperature tensile properties of as-deposited alloy were investigated. The results show that the macrostructure of the novel alloy contains large columnar grains and small columnar grains. Compared to the reference alloy Ti-6Al-4V manufactured with the same process, the novel alloy had much finer basket-weave microstructure. This novel alloy, solid-solute with alloying elements Mo, Zr and Si, has higher microhardness and better combination of strength and plasticity compared to Ti-6Al-4V. [ABSTRACT FROM AUTHOR]

The near-β titanium alloy Ti-5Al-5Mo-5V-1Cr-1Fe (Ti-55511) was treated by laser surface remelting (LSR) with a series of holding times at 500 °C in order to study the growth behavior of ω-assisted α phase and its effect on mechanical properties. Transmission electron microscope and hardness test was used to characterize different phases and surface property of different samples. Results show that only a small quantity of athermal ω phases precipitate from β matrix at the remelted zone and there are incomplete collapsed {111} β lattice planes at the β/ω boundaries because Ti-55511 has low electron/atom ratio and high Al contents. So the athermal ω phase precipitated during LSR process has little effect on increasing surface hardness of Ti-55511. ω-Assisted nano-scaled α lamellas can be formed by the connection of some initial α phases at the early stage of low temperature isothermal heat treatment. And all the ω phase dissolved after 500°C/10min. Further increasing of holding times will cause volume fractions increase of the nano-scaled α lamellas, resulting in gradually improving hardness of the alloy at the remelted zone. [ABSTRACT FROM AUTHOR]