Microstructures and mechanical properties of laser rapid formed Ti-6Al-4V alloy

The Laser Rapid Forming (LRF) has been used to build up default free and nonoxidation Ti- 6Al- 4V samples in atmosphere controlled LRF equipment. The microstructure and mechanical properties of as-deposited and heat-treatment are analyzed. It has been found that the macrostructure of as-deposited Ti-6Al- 4V alloys takes the shape of huge columnar prior beta grains (P β G) with continuous boundary and epitaxial growth along the vertical direction (Z) of the laser scanning. Between cladding layers there are bands of coarse structures resulting from the reheating by laser beam when the prior cladding layers forming. The substructure in prior beta grains is mainly of the fine acicular a and basketweave matrix of α+β. After high temperature annealing treatment, little basketweave matrix of α+β remains and the acicular a changes into a laths with clear β outlines. After quenching-aging treatment, the substructures are mainly of the α laths and basketweave matrix of α+β. Multi-quenching -aging heat treatments produce bi-modal structure. The physical property test shows that the tensile strength and plasticity at the vertical direction (Z) of the laser scanning are higher than those at the direction of parallel (X). After high temperature-annealing treatment, the Ti-6Al-4V alloy has lower level of tensile strength and plasticity while quenching-aging treatment decreases tensile strength and increases plastic slightly.