Effect of matrix content and pre-sintering-assisted liquid-phase sintering on the microstructure, stereology, and mechanical behavior of W–Ni–Fe tungsten heavy alloys

W–Ni–Fe tungsten heavy alloys (WHAs) are attractive for structural and functional applications requiring high density, strength, and mechanical reliability. However, achieving near-full densification together with microstructural stability and ductility remains challenging in tungsten-rich compositions. In this study, W–Ni–Fe alloys containing 80–98 wt.% W were fabricated by powder metallurgy using a conventional tubular-furnace route under flowing hydrogen. The effects of pre-sintering-assisted liquid-phase sintering (LPS) on densification, stereology, microstructural evolution, and mechanical behavior were then systematically investigated. The intermediate pre-sintering step reduced residual porosity and improved Ni–Fe matrix distribution. As a result, it produced a more homogeneous two-phase microstructure than direct sintering. Quantitative stereological analysis showed that relative density, tungsten contiguity, connectivity, and dihedral angle (φ[jls-end-space/]) were strongly dependent on matrix content. Within the deliberately broad matrix-content series, 90W–7Ni–3Fe exhibited the most favorable combination of near-full density (98.8%), negligible visible porosity, retained cylindrical geometry without visible slumping, and balanced stereological characteristics. This composition is therefore treated as the best condition among those tested rather than as a universal compositional optimum. In this selected alloy, densification was largely completed during the early stage of sintering, while longer holding mainly caused controlled tungsten grain growth. Tensile testing showed high strength with measurable ductility and modest positive strain-rate sensitivity. Hardness evolution and fractographic observations indicated that deformation and fracture were governed primarily by matrix-mediated plasticity. Ductile matrix tearing was accompanied by localized tungsten–tungsten debonding. These mechanical data support the selected 90W–7Ni–3Fe condition, while the composition series primarily establishes the density, porosity, shape-retention, and stereological basis for its selection. The results show that pre-sintering-assisted LPS can produce dense, shape-stable W–Ni–Fe alloys with measurable tensile plasticity using a conventional LPS-compatible furnace route without specialized consolidation equipment.