Eutectic structure induced by ordering of solute atoms leading to strengthening effects

Abstract

In this study, Zr atoms transition from a disordered state to a short-range ordered state due to increased diffusion drive in high Zr content brazed joints. This atomic ordering leads to alternate nucleation of Ti2Ni/Ti2Cu and Zr2Ni/Zr2Cu primary phases along the same crystallographic direction, and the β-(Ti, Zr)2(Cu, Ni) eutectic structure with the <101> orientation is formed in the brazed joints. The growth of this eutectic structure absorbs the lattice distortion energy and reduces the number of low-angle grain boundaries. With the Zr content increased from 12 wt% to 37.5 wt%, low-angle grain boundaries can transfer to high-angle grain boundaries in the eutectic structure, enhancing the boundary misorientation about 53 %. The high misorientation hindered movable dislocations making them aggregated near the grain boundaries, which produce the eutectic structure strengthening effect. It increased to 726 MPa in the tensile strength of brazed joint with 20 wt% Zr content. This study has greatly improved our understanding of the intricate interactions between the ordering and strengthening of eutectic structures.