Gradient structure induced by molybdenum in 90W–Ni–Fe heavy alloy

• A new way of fabricating 90W–Ni–Fe heavy alloy with gradient structure is inspired by the FG WC–Co material.
• The obtained gradient structure in grain size and micro-hardness of the binding phase varied greatly.
• The phenomenon of liquid phase migration existed and was studied.

90W(Mo)–Ni–Fe heavy alloy with gradient structure was fabricated by the diffusion of Mo slice from the alloy's surface at 1480 °C. The microstructure and content of binding phase at different regions along the cross section in the samples were investigated by scanning electron microscopy (SEM). The Mo content was determined by energy dispersive analysis (EDS) and the hardness of matrix phase was measured by Vickers' micro-hardness tester. Results show that the grain size, the volume fraction of binding phase and the hardness of matrix phase vary gradually due to the graded distribution of molybdenum. Simultaneously, the interfacial tension gradient induced by the dissolution of molybdenum is the driving force for liquid phase migration during liquid phase sintering.