Abstract: By using optical microscope, scanning electron microscope and electronic universal testing machine, effect of time of solution and aging treatment on microstructure and mechanical properties of TC4 (Ti6Al4V) alloy fabricated by selective laser melting (SLM) was investigated. The results show that the annealed SLM-fabricated TC4 alloy is mainly composed of continuous α_GB, basketweave α and transformed β phases. After solution and aging treatment, the microstructure of the specimens all presents as the morphology of basketweave. Under the condition of solution treatment at 920 ℃ and aging process of 550 ℃×3 h, air cooring, with the solution time increasing from 2 h to 6 h, the primary α phase(α_P) is significantly coarsened and the length of part α_P is up to 16 μm. The lamellar α phase is also coarsened and the length of lamellar α phase increases from 5-15 um to 20-30 um. The continuous α_GB phase becomes discontinuous and its width increases from 2.7 μm to 4.4 μm. Meanwhile, there is largersize α colony presented. The tensile strength increases from 1045.2 MPa to 1156.9 MPa, the elongation decreases from 13.6% to 6.7%. Under the condition of aging at 550 ℃ and the solution process of 920 ℃×2 h, WQ, with the aging time increasing from 3 h to 8 h, the fraction of transformed β phase increases. The length of α_P phase decreases from 40-60 μm to 30-40 μm. The α_GB phase is also continuous while its width increases from 2.7 μm to 4.5 μm. The lamellar α phase coarsens slightly. The tensile properties do not change remarkably. Therefore, it can be concluded that the duplex microstructure is difficult to obtain by changing time of solution and aging treatment at solution temperature of 920 ℃ and aging temperature of 550 ℃ for the SLM-fabricated TC4 alloy, and it has no beneficial effect on improving comprehensive mechanical properties.

Key words: selective laser melting, TC4 titanium alloy, solution and aging treatment, microstructure, mechanical properties