Laser powder bed fusion of tungsten alloy containing a high content of low-melting-point metallic phase: Densification behavior, microstructure evolution, and mechanical properties

To mitigate the inherent brittleness of pure tungsten, strategic additions of relatively low-melting-point metals such as nickel (Ni) and iron (Fe) are typically incorporated to enhance the toughness of alloy. Laser additive manufacturing (LAM) technology presents a novel approach for fabricating complex-structured tungsten alloy components. However, a critical technical challenge emerges during the LAM process: the fundamental conflict between maintaining sufficient energy input to achieve complete melting of the high-melting-point tungsten matrix and minimizing the vaporization loss of low-melting-point metallic phases under intense laser thermal effects. In this study, tungsten alloy with a high content of low-melting-point metallic phases (93 W) was synthesized via ball milling followed by LPBF processing. The effects of laser energy density (E_d) on the densification, microstructure, and mechanical properties of the 93 W alloy were systematically explored. The results demonstrated the formation of significant unmelted pores when E_d was below 800 J/mm³. For energy densities ranging between 800 J/mm³ and 1000 J/mm³, the tungsten particles completely melted, resulting in 93 W-Ni-Fe specimens with densities greater than 95 %. However, when E_d exceeded 1000 J/mm³, microscopic cracks emerged, causing a decline in relative density. At the optimal laser energy density of 900 J/mm³, the 93 W-Ni-Fe alloy exhibited equiaxed columnar grains, with a compressive strength and fracture strain of 2020.6 MPa and 30.9 %, respectively. This study provides a comprehensive analysis of the microstructural and mechanical properties of tungsten alloys with high low-melting-point metal content produced via LPBF, offering valuable insights for the advanced manufacturing of high-performance tungsten heavy alloy components.