93W–5.6Ni–1.4Fe heavy alloys with enhanced performance prepared by cyclic spark plasma sintering

Bulk 93W–5.6Ni–1.4Fe heavy alloys were prepared by an optimum sintering schedule and post-heat treatment using spark plasma sintering (SPS) technique. The microstructural parameters of the alloys, including tungsten grain morphology, tungsten grain size and W–W contiguity, are highly related to the heat treatment conditions. After cyclic heat treatment at 1400 °C with one cycle, the alloy shows fine near-spherical tungsten grains embedded in the matrix phase with decreased W–W contiguity. The alloy exhibits improved bending strength (about 1700 MPa) and yield strength (about 1100 MPa at room temperature and about 700 MPa at 800 °C), due to the microstructural modification. The bending fracture morphology is characterized as tungsten–tungsten intergranular separation, tungsten transgranular cleavage, matrix ductile rupture and local matrix rupture on the separated W–W interfaces. The room temperature yield strength of the spark plasma sintered 93W–5.6Ni–1.4Fe heavy alloys are dependent on the microstructural factors such as tungsten grain size, matrix volume fraction and tungsten–tungsten contiguity.