Performance enhancement of laser powder bed fusion Ti6Al4V via a novel ultrahigh speed shock approach using two developed setups

Abstract

Pores and residual tensile stress are inevitable in laser powder bed fusion (LPBF), degrading the overall properties of the fabricated components. To address these challenges, a novel ultrahigh speed shock (UHSS) approach is proposed, in which a projectile reaches a velocity of 2.35 km/s using two custom-developed setups. The approach involves additive manufacturing with a self-made LPBF machine, followed by shock treatment with a custom-made two-stage light gas gun system. The velocity was optimized through molecular dynamics simulations and theoretical calculations. After UHSS, the tensile strength of Ti6Al4V increased from 1182.9 to 1576.8 MPa, representing a 33.3 % improvement while maintaining ductility. Additionally, the friction coefficient and wear rate under a 5 N load decreased from 0.733 and 6.475 × 10^–4 mm³/N∙m to 0.562 and 4.471 × 10^–4 mm³/N∙m, corresponding to reductions of 23.3 % and 31.0 %, respectively. The electric resistance increased from 1.63 to 2.28 MΩ‧cm² under UHSS, representing a 39.9 % improvement. Micro-computed tomography revealed that porosity approached zero after UHSS. Moreover, electron backscatter diffraction revealed a 41.8 % reduction in average crystallite size from 1.22 to 0.71 μm after UHSS. The enhanced properties are attributed to grain refinement, pore reduction, and the introduction of compressive stress. The proposed UHSS approach and two developed setups offer a new route for fabricating Ti6Al4V with remarkable properties, potentially applicable in extreme environments.