Microstructure and Tensile Properties of Laser Solid Formed TC4 Alloy

TC4 alloy was prepared by laser solid forming (as-deposited) and then annealed. The microstructure and tensile properties of the as-deposited and annealed alloy were studied and compared with those of convertional TC4 alloy. The results show that the as-deposited microstructure of laser solid formed alloy consisted of needle-shaped martensite α and β phases. The original β grain boundaries were observed clearly. The annealed microstructure was composed of α lath and β phase between laths. Comparing with the as-deposited structure, the volume fraction of α phase in the annealed structure increased and the α lath became coarse. The tensile properties of the laser solid formed alloy in as-deposited and annealed states were better than those of annealed conventional TC4 alloy. The annealing treatment decreased the property difference of the alloy between directions vertical and parallel to the scanning direction. Comparing with those of the as-deposited alloy, the tensile strength and yield strength of the annealed alloy decreased while the elongation and reduction of area increased. The tensile properties in vertical to the scanning direction of the as-deposited alloy and annealed alloy had little difference. The tensile fracture of the as-deposited and annealed alloys both showed a dimpled characteristic, and the fracture mechanism was ductile.