Influence of Heat Treatment on Microstructure and Mechanical Properties of TC4 Fabricated by Laser Melting Deposition

The phase composition, microstructure, tensile properties of TC4 samples produced by laser melting deposition (LMD) and LMD followed by solution-aging treatment were investigated to explore a simpler approach to improve the mechanical performances and eliminate negative influences by post treatment. The as-deposited TC4 microstructure showed a combination of α΄martensite and α-colony with various shapes, such as acicular, rod-like and lamellar. As a synergistic result of solution and aging treatment, the dispersion strengthening of secondary-α as well as optimization on length-width ratio of primary-α and volume fraction of β-phase cause an increase in the ductility and strength. Meanwhile, there is a difference between microstructure of water-quenched specimens and air-cooled specimens, subsequently playing a key role in properties. The solution with air-cooling and aging is comparatively found to significantly reduce the anisotropy and improve comprehensive performance.