A strong-ductile niobium alloy enhanced by eutectic Nb2C

Abstract

Niobium alloys are widely applied in aerospace technologies. Traditional niobium alloys suffer from insufficient high-temperature strength or limited room-temperature plasticity. Here, we develop novel Nb2Mo0.5W0.5Cx eutectic niobium alloys by introducing refractory alloying elements and carbide inspired by design concept of multiprincipal alloy and carbide eutectic alloys. The Nb2Mo0.5W0.5Cx alloys contain numerous eutectic structures consisting of body-centered cubic (BCC) solid solution and carbide phases, in which the carbide phase transfers from Nb2C to NbC with the increase of C addition. By optimizing the composition, a Nb2Mo0.5W0.5C0.25 niobium alloy consisting of BCC and Nb2C with strong bonded semi-coherent interface exhibits a high yield strength of 1.27 GPa, compressive strength of 2.03 GPa, and good plasticity with a fracture strain of 17.8%. Solid solution strengthening from alloying elements and second phase strengthening from carbide phases contribute to the high strengths, while the plasticity is improved mainly from fine grain strengthening and strong bonding of phase interface by reducing the interfacial energy and slowing down the crack propagation. This study offers a strategy for designing the high-performance refractory alloys to bypass the content limitation of alloying elements and enhanced ceramics that generally reduce plasticity.