Refined Microstructure and Enhanced Mechanical Properties of 93W–4.9Ni–2.1Fe–1La2O3 Alloy Fabricated by a Two-Stage Sintering Process.

In this work, high-performance 93W–4.9Ni–2.1Fe–1La₂O₃ (wt pct) alloy was fabricated by a two-stage sintering method and subsequent vacuum heat-treatment, which had a high densification degree (99.4 pct) and fine grain sizes of W (only 9.76 μm). The utilization of ultrafine W–Ni–Fe composite powder, addition of La₂O₃ particles and optimized sintering technique effectively resulted in structure refinement. Moreover, the second-phase particles were mainly dispersed at grain boundaries (GBs), besides a small amount of them in the interior of W grains. The as-prepared alloys after sintering first at 1400 °C for 2 hour and then at 1500 °C 30 minutes exhibited enhanced mechanical properties, with a maximum tensile strength of ~ 1024 MPa, elongation of ~ 22.7 pct and hardness of ~ 457 HV₁. The excellent strength could be attributed to various mechanisms, namely fine-grained strengthening and oxide dispersion strengthening. Meanwhile, the ductilization is predominantly benefitted from a synergistic effect of low angle grain boundaries, intragranular oxide particles and vacuum heat-treatment process. This work not only promotes the development of oxide-reinforced WHAs for challenging engineering applications but also provides a new perspective for the design of refractory composite materials. [ABSTRACT FROM AUTHOR]