Study on microstructure and mechanical properties of LDM-SLM hybrid manufactured Ti6Al4V titanium alloy

Laser addictive manufacturing(AM) of titanium alloys have great potential in aerospace field, as its unique advantages in small complex structure fabricaton and large components near-net shape forming. In order to achieve the fabrication of large components with complex structure just in one piece, the laser deposition manufacturing(LDM) was carried out with Ti6Al4V alloy as the basis by selective laser manufacturing(SLM). The attained samples which had two distinguishing AM processes, was conducted annealing treatment at different temperatures to explore the evolution of microstructure and mechanical properties. The result shows that the microstructures of Ti6Al4V alloy structure prepared by the LDM-SLM processes consists of three zones:LDM zone mainly composing laths, SLM zone dominated by slender acicular ' martensite and heat affected zone (HAZ) formed by remelting which is mainly composed of lath and ' martensite. In mechanical properties, the as-built component has the characters of high strength with low plastic, and significant anisotropy; samples annealing at 850℃ exhibit the best comprehensive mechanical properties because of the reasonable balance between the strength and the plastics. Work hardening in the tensile process leads to double necking of the tensile bar after 850℃ annealing.