Improving the mechanical properties of Nb-24Ti-16Si-2Al alloy by adding Zr and Fe to regulate silicide

The main constituent silicides have a decisive influence on the mechanical properties of Nb-Si based alloy. In this work, the silicide of Nb-24Ti-16Si-2Al alloy is regulated and its properties are optimized through the synergistic addition of Zr and Fe. Results show that the formation of the (Nb, X)₃Si phase is repressed in the optimized alloy, and the constituent phases switches from Nbss + (Nb, X)₃Si + β-(Nb, X)₅Si₃ to Nbss + Nb₄FeSi + γ-(Nb, X)₅Si₃. The doping of Zr content can gradually enhances the proportion of γ-(Nb, X)₅Si₃, and refine the eutectic colonies. Element Fe mainly controls the formation and proportion of Nb₄FeSi phase. A transition area exists between the Nb₄FeSi and γ-(Nb, X)₅Si₃ interfaces, displaying an indistinct grain boundary of Nb₄FeSi. The appearance of hexagonal γ-(Nb, X)₅Si₃ block is conducive to improving room temperature toughness and compressive strength. The highest K_Q value with a mean of 14.84 MPa·m^1/2 is determined in the 8Zr-2Fe alloy, improved by 126.2% compared with the initial alloy. The 8Zr-6Fe alloy exhibits excellent room temperature compressive strength, about 2006 MPa, improved by 64.56%. Besides, the high proportion of Nb₄FeSi phase will reduce the high temperature compressive strength, which is beneficial to the thermomechanical processing of the alloy.