Enhanced strength–plasticity synergy of copper composites by designing uniformly dispersed yttria nanoparticles and a heterogeneous grain structure

Designing heterogeneous grain structure (HGS) has been proven to be an effective strategy for overcoming the strength-plasticity dilemma in copper and copper alloys. However, the construction of HGS in dispersion-strengthened copper (DSC) for enhancing strength-plasticity synergy remains challenging. Here, we proposed a novel method, multistep ball milling and reduction process followed by spark plasma sintering, to prepare DSC with an HGS to ameliorate the strength-plasticity dilemma in DSC. Micron- and nano-CuO and nano-Y₂O₃ powders were chosen as raw materials in this new method. The Cu-7 vol% Y₂O₃ composite, exhibiting a compressive yield strength of 438 MPa and a failure strain of 46.3%, exhibits a superior strength-plasticity tradeoff in comparison with other DSC materials. Systematic experiments indicate that the back-stress at the heterointerfaces between coarse grains and fine grains maybe not only raise the yield strength of Cu-Y₂O₃ composite, but also significantly enhance the strain hardening to increase the plasticity of the material. The new HGS designing route in this study offers a feasible pathway to develop DSC with a remarkable enhancement in strength and plasticity.