Effect of Heat Treatment on Microstructure and Properties of Laser Deposition TC4

By comparing the microstructures, static mechanical properties and microhardness of laser deposition TC4 alloy in the as-deposited and heat-treated states, the approaches to perfect the microstructure of laser deposition TC4 alloy were explored. Results show that after the as-deposited sample undergoes 970 degrees C heat treatment, the grain boundary alpha is thoroughly broken which is continuous initially; with the extension of solution time, globular a phases are more and bigger, and their laths are in full growth and increase dramatically; 2 h later, when the sample undergoes aging treatment, its structure turns to be constituted by equiaxed alpha, basketweave alpha and transformed beta phase, which results in the optimized textural parameters. Compared with that of as-deposited and annealed samples, the plasticity of the solution aging sample is enhanced significantly and the strength is decreased slightly, and their integrated mechanical properties improve remarkably. Its equiaxed structure performs coordinating function and its basketweave structure can reduce the dislocation pile-up to improve the plasticity. The microhardness is gradually increased in the laser deposition TC4 alloy in the order of the as-deposited, as-annealed, as-solution aged and as solid-solution treated. But when the solution temperature rises to the transformation point, the microstructure of the sample rearranges after crystallizing, leading to marked decline in microhardness.