A novel dynamic technique to form reverse grain size gradient microstructure in pure copper

Abstract

Gradient microstructure-engineering is a very effective and low-cost strategy for high strength without compromising ductility in many crystalline materials. Conventional gradient materials (i.e., fine-grained surface and coarse-grained core regions) are usually fabricated by surface modifications at very low strain rate. In the present work, we reports a novel reverse grain size gradient microstructure (i.e., fine-grained core and coarse-grained surface regions) fabricated using a dynamic simple shear process. EBSD observations have revealed the microstructure transition from uniform grain size distribution to reverse grain size gradient microstructure in pure copper under a high strain rate (~105 s−1) and large imposed shear strain. Meanwhile, profuse deformation twins are also introduced in this reverse gradient-structured copper. Ultimately, our work develops a novel strategy or technique to properly tailor microstructure to achieve a substantial improvement of mechanical properties in gradient-structured materials.