Influence of heat treatment on the microstructure and properties of Ti-6A1-4V titanium alloy by laser rapid forming

The influence of heat treatment on the microstructures was investigated for Ti-6Al-4V alloy by laser rapid forming (LRF) process. The results indicate that the microstructures of sample by LRF consist of coarse columnar β grains with average grain width of 300 μm, which grew epitaxial from the substrate along the deposition direction Z. For the as-deposited samples, the microstructures of original β-Ti grains are composed of acicular α and Widmanstatten a laths and have an obvious tendency to coarsen by annealing treatment. And the microstructures consist of a triplex mixture of equiaxed α, basketweave α lath and transformed β by solution-aging treatment. The original and continuous a phase in the grain boundary was broken up and became un-integrated, even disappeared. Furthermore, the width of a laths increased and the aspect of a laths decreased. As a result, the room temperature tensile strength of the samples made by LRF are superior to that of the general forging sample (ASTM B381-05), and the comprehensive mechanical properties are improved obviously through the solution-aging treatment.