Improving the ductility of Al matrix composites through bimodal structures: Precise manipulation and mechanical responses to coarse grain fraction

In this work, a powder metallurgy-thermomechanical method was proposed to fabricate bimodal composites with the forward design of coarse grain fractions. By optimizing chemical composition and sintering-extrusion parameters, precise manipulations of bimodal structures combining ultrafine and coarse grains have been realized. Bimodal structures lead to extra hardening and strain hardening, enhancing the ductility of ultrafine grained composites. Higher coarse grain fractions introduce more soft-hard domain interfaces in bimodal composites but decrease the strain hardening ability of domain interfaces. This work proposes a strategy to tailor the heterostructures quantitatively and deepens insight into the influences of coarse grain fraction on mechanical behaviors of bimodal composites.