Precious control of the soft-zone width to achieve strength-ductility synergy in heterogeneous B₄C/7075Al composites

Dispersion-strengthened metal matrix composites exhibit enhanced strength but reduced ductility, presenting a challenge in strength-ductility synergy. Here, we proposed a simple but effective strategy combining powder size grading with pressure infiltration to construct heterogeneous structures in B₄C/7075Al composites. The soft-zone width could be precisely tuned by changing the diameter of the raw 7075Al powder, and the measured value of the soft-zone width was very close to the theoretical value, indicating that the soft-zone width was predictable. The heterogeneous B₄C/7075Al composites dasda with optimized soft-zone widths achieved a fracture elongation of 9.6 %, comparable to that of the 7075Al while maintaining ultimate tensile strength close to that of the homogeneous composites. Due to the mechanical incompatibility between the hard and soft zones, high-density geometrically necessary dislocations piled up against the hetero-zone boundaries, resulting in significant hetero-deformation-induced strengthening and strain hardening effects, which contributed to the enhanced synergy between strength and ductility.