Promoting grain boundary migration in CuAlMnCo alloy via nanoprecipitate-enhanced dislocation engineering

Abstract

The superelastic properties of shape memory alloys (SMAs) depend strongly on their large-sized grains. Improving grain boundary (GB) migration velocity is a key to obtain large-sized grains. In this study, a multiplicative increase in GB migration velocity was achieved through tuning dislocation configuration and density by nanoprecipitates in a polycrystalline CuAlMnCo alloy. Owing to the pinning effect of the B2 nanoprecipitates, the dislocation density increased slightly, and the dislocation configuration changed from straight-like to bowed-out and tangled-like. This special dislocation configuration contributed to the formation of fine subgrains (26.0 μm) with a high misorientation (0.48°), which strongly promoted GB migration. As a result, a GB migration velocity of up to 7.1 × 10⁻⁶ m s⁻¹ was observed in the polycrystalline CuAlMnCo alloy with B2 nanoprecipitates^. An average grain size of 1.2 cm was obtained in the polycrystalline CuAlMnCo alloy containing B2 nanoprecipitates, approximately three times larger than that of the counterpart without nanoprecipitates. An excellent superelastic strain of 8.4 % was achieved in polycrystalline CuAlMnCo alloy by introducing B2 nanoprecipitates.