Achieving strength-ductility synergy in semi-solid squeeze cast 6TiB2/Al–17Si–4Cu composites by heat treatment

Abstract

This study aims to achieve synergistic strength-ductility enhancement of semi-solid squeeze cast 6TiB2/Al–17Si–4Cu composites through in-situ particle strengthening and T6 heat treatment. The microstructure and mechanical properties of 6TiB2/Al–17Si–4Cu composites with different heat treatments were investigated. TiB2 particles are semi-coherent with α-Al and primary Si, respectively. The nanoscale precipitate phases were determined by their crystal orientation relationships. The results showed that they are θ and θʹ phases. Meanwhile, the research results pertaining to the mechanical properties imply that the strength and ductility are enhanced by the TiB2 particles and Al2Cu precipitates. The optimum heat treatment process (solution treatment for 9 h at 520 °C and aging for 8 h at 170 °C) of strengthened 6TiB2/Al–17Si–4Cu composites is revealed in this study, when the ultimate tensile strength and elongation of the composites are 263.3 MPa and 0.51%, respectively. The mechanisms governing the enhanced strength and ductility of 6TiB2/Al–17Si–4Cu composites were discussed.

Keywords

• Strength-ductility synergy
• Microstructures
• TiB2 particles
• Al2Cu precipitates
• T6 heat treatment