Improved mechanical properties of W-Zr-Ti-Nb alloys via adding Ti and Nb

Formation of the W₂Zr intermetallic is the key reason for the low relative density and brittleness of W-Zr alloys. In this study, 65 W-Zr-Ti-Nb alloys with different Ti and Nb content were prepared by powder metallurgy. With the increase of Ti and Nb content, the proportion of the W₂Zr in the alloy decreases, causing the densification of 65 W-Zr-Ti-Nb alloys. The thermodynamic calculation shows that the addition of both Ti and Nb results in a narrowing stabilized temperature range of W₂Zr and an expanding stabilized temperature range of BCC-WTi_xNb_y, respectively, ultimately causing the disappearance of the W₂Zr and formation of the WTi_xNb_y during non-equilibrium cooling. Both high ductility and strength can be achieved in the W-Zr-Ti-Nb alloys by assistance of the disappearance of the brittle W₂Zr phase and the formation of the ductility WTi_xNb_y. The first principle calculation indicates that the co-doping Ti and Nb results in a larger expansion on the spacing of the {110} close-packed plane and a smaller expansion or even shrinkage on the atomic spacing along the close-packed direction of the WTi_xNb_y. Further, integrated crystal orbital Hamilton population (ICOHP) results proved that the bonding strength of W-Ti and W-Nb was weaker than that of W-W in WTi_xNb_y. Both increased spacing of {110} plane and decreased interatomic bonding strength aid in reducing Peierls-Nabarro stress, promoting plastic deformation. This study provides a new method for improving mechanical properties by tailoring the phase constitution in W-Zr alloys through co-doping Ti and Nb.