Two optimized post-heat treatments to achieve high-performance 90W–7Ni–3Fe alloys fabricated by laser-directed energy deposition

Abstract

Preparing tungsten heavy alloys with high strength and toughness by laser-directed energy deposition (LDED) is challenging. Here, we obtained high-performance LDED-fabricated 90W–7Ni–3Fe (90W) alloys through two optimized post-heat treatments. The results show that the 90W sample achieves a superior combination of the ultimate tensile strength (UTS: 821 ± 26 MPa) and ductility (17.46 ± 2.93%) after the high-temperature and long-time heat treatment, which are comparable to or even better than those of 90W alloys processed by powder metallurgy methods. The superior ductility is attributed to the improvement of the matrix-phase coordinated deformability, the enhancement of the W-M interfacial bonding strength, and the involvement of W particles in the coordinated deformation during tensile testing. In addition, the cycle-short-time heat treatment can simultaneously improve the UTS and elongation of the as-fabricated sample. The significant improvements in UTS (834 MPa → 870 MPa) and elongation (3.44% → 6.96%) are mainly related to the increase of W particles cleavage, the improvement of W-M interfacial bonding strength, and the reduction of porosity in the microstructure. This work provides a theoretical guide for improving the mechanical properties of tungsten alloys manufactured by additive manufacturing (AM) technology, which can be beneficial for expanding the application of AM technology in the field of tungsten alloys.