Ti–6Al–4V alloy prepared by laser powder bed fusion of a coarse powder

Abstract

ABSTRACT A Ti–6Al–4V (wt%) alloy was prepared by laser powder bed fusion (LPBF) of a coarse powder with particle sizes in the range of 50–200 μm. The effect of volume energy density (VED) on cavities/pores, microstructure and mechanical properties of the LPBF-fabricated samples was investigated. The results showed that with the increase of VED, the content of cavities/pores decreased. When the VED was 100 J/mm3 and above, the content of cavities/pores decreased to below 0.3%, and the yield strength (YS), ultimate tensile strength (UTS) and elongation to fracture reached 1032, 1052 MPa and 7.0%, which are close to the tensile properties of Ti–6Al–4V alloy prepared by LPBF of a fine powder (particle sizes: 15–53 μm). The microstructure of the samples consisted of β-columnar crystals containing acicular α′ martensite. After vacuum annealing at 800°C and 900°C respectively, the microstructure of the fabricated samples changed to an α+β lamellar structure, with a substantial decrease in YS and UTS to 836 and 919 MPa, respectively, but a significant increase in elongation to fracture to 15.9%, resulting in very good overall tensile properties. This study shows that with a sufficient VED and proper heat treatment, a Ti–6Al–4V alloy with good metallurgical quality and excellent overall tensile properties can be fabricated by LPBF of a coarse powder.