Rapid sintering of ultrafine-grained refractory metals under mild conditions

Refractory metals are promising for aerospace and nuclear applications because of their high melting points and stability. However, the processing procedure still encounters challenges due to the high melting point and strong bond strength resulting from the high delocalized electron density of refractory metals. Here we show that liquid metals can dilute this electron density and weaken bond strength, enabling the efficient extraction, dissolution and recombination of refractory metal atoms. This strategy allows the fabrication of bulk refractory materials at notably lower temperatures (<1,000 °C) in a very short time (~2 min). Using this liquid metal-assisted sintering mechanism, we successfully sintered various refractory metal bulks (including W, Re, Ta, Nb, Mo, V, Cr and Ti), achieving equiaxed ultrafine-grained microstructures with excellent yield strength. This mild preparation condition also offers high flexibility for producing alloys, gradient structures and dispersion-strengthened materials, representing an important milestone in developing high-performance refractory structural materials.