Exceptional Superelasticity via Heterogeneity-Driven Texture Optimization in Equiaxed CuAlMn Alloys
Exceptional Superelasticity via Heterogeneity-Driven Texture Optimization in Equiaxed CuAlMn Alloys
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摘要: Achieving high superelasticity in polycrystalline shape memory alloys (SMAs) is fundamentally limited by strain incompatibilities arising from grain orientation. Realizing high martensitic transformation strain (εTS) orientations that are favorable for superelasticity in equiaxed microstructures remains a major challenge. Here, a novel heterogeneity-driven texture optimization strategy is reported to enhance superelasticity in CuAlMn alloys through controlling high-εTS orientations. Controlled deformation imprints dislocation density heterogeneity in differently oriented grains, leading to the gradients of sub-boundary energy. These gradients drive selective grain boundary migration, facilitating the preferential growth of grains with the high- εTS <015> orientation. As a result, the fraction of <015>-oriented grains increases significantly from ~19% to ~70%, yielding a unprecedent tensile superelastic strain of ~8.0% in equiaxed CuAlMn alloys, paving the way for practical engineering applications. This microstructural heterogeneity-guided strategy offers a general framework for overcoming texture-related limitations in polycrystalline functional materials.Abstract: Achieving high superelasticity in polycrystalline shape memory alloys (SMAs) is fundamentally limited by strain incompatibilities arising from grain orientation. Realizing high martensitic transformation strain (εTS) orientations that are favorable for superelasticity in equiaxed microstructures remains a major challenge. Here, a novel heterogeneity-driven texture optimization strategy is reported to enhance superelasticity in CuAlMn alloys through controlling high-εTS orientations. Controlled deformation imprints dislocation density heterogeneity in differently oriented grains, leading to the gradients of sub-boundary energy. These gradients drive selective grain boundary migration, facilitating the preferential growth of grains with the high- εTS <015> orientation. As a result, the fraction of <015>-oriented grains increases significantly from ~19% to ~70%, yielding a unprecedent tensile superelastic strain of ~8.0% in equiaxed CuAlMn alloys, paving the way for practical engineering applications. This microstructural heterogeneity-guided strategy offers a general framework for overcoming texture-related limitations in polycrystalline functional materials.