Effect of laser energy density on microstructural evolution of selective laser melted Ti-15Zr alloy

Selective laser melting (SLM) has been widely applied to the design and production of alloys due to the efficiency in processing components with complex structures and large sizes, especially Ti alloys. However, SLMed Ti alloys always exhibit undesirable ductility since the amount and morphology of the acicular alpha ' martensite phase are difficult to control. In this study, a SLMed Ti-15Zr alloy with an excellent combination of strength (a yield strength of 792 +/- 11 MPa, an ultimate strength of 837 +/- 13 MPa) and ductility (18.7 +/- 0.5 %) was successfully fabricated by adjusting laser energy density (E) during the SLM process and the sub-sequent heat treatment. The influence of E on densification and microstructural evolution was investigated. When E is in the range of 69-125 J/mm3, Ti-15Zr alloys can achieve a relative density greater than 99 %. With the increase of E, the coarse equiaxed alpha phase decreases, and the fine lamellar alpha phase increases in the alloys after the heat treatment, owing to the slow cooling rate in the molten pool at high E. The excellent mechanical properties were attributed to the coordinated effects of the coarse equiaxed alpha phase and the fine lamellar alpha phase. (c) 2022 Elsevier B.V. All rights reserved.