Ductile Re_0.1Ta_1.9W_0.2C_x refractory alloys with excellent elevated-temperature strength

The inverse relationship between high-temperature strength and room-temperature plasticity of refractory alloys poses a significant challenge for developing ultra-high-temperature materials. Here, four types of Re_0.1Ta_1.9W_0.2C_x (x = 0,0.05,0.25 and 0.4) refractory alloys were fabricated using the vacuum arc melting method. These alloys exhibit remarkable high-temperature strength and exceptional room-temperature compression plasticity. The Re_0.1Ta_1.9W_0.2 alloy has a single body-centered-cubic (BCC) solid solution phase and a yield strength of 345 MPa at 1450 °C, with a compressive fracture strain of 31.7 % at room temperature. After adding a small amount of carbon (2.27 at.%), the main phase of the Re_0.1Ta_1.9W_0.2C_0.05 alloy continues to be the BCC phase, with a significant quantity of dispersed micro/nano-scale plate-like carbides precipitated within the BCC grains. The high-temperature strength of the Re_0.1Ta_1.9W_0.2C_0.05 alloy increases by 29 % compared to the Re_0.1Ta_1.9W_0.2 alloy while maintaining superior room-temperature compression ductility (compressive fracture strain at 29.6 %). Upon elevating the carbon content to 11.4 at.%, the Re_0.1Ta_1.9W_0.2C_0.25 alloy displays a hypo-eutectic structure comprising BCC and Ta₂C. The compressive fracture strain of the Re_0.1Ta_1.9W_0.2C_0.25 alloy at room temperature (21.8 %) exceeds that of the NbMoTaW alloy by a factor of 8.4, while its yield strength at 1450 °C (710 MPa) is 68.6 % greater than that of the NbMoTaW alloy. However, when the carbon content in the Re_0.1Ta_1.9W_0.2C_x alloy reaches 18.2 at.%, there is a decline in high-temperature strength and room-temperature compression ductility in comparison to the Re_0.1Ta_1.9W_0.2C_0.25 alloy. The precipitation of micro- and nano-scale plate-like Ta₂C phases within the matrix serves dual roles as both a barrier to dislocation movement and a medium for dislocation sliding, thus enhancing the high-temperature strength of the Re_0.1Ta_1.9W_0.2 alloy while retaining exceptional room-temperature compression plasticity. The Re_0.1Ta_1.9W_0.2C_0.05 and Re_0.1Ta_1.9W_0.2C_0.25 alloys exhibit excellent mechanical properties at room and high temperatures, suggesting their potential application in ultra-high-temperature material.