Enhanced strength and ductility of TiB2/AA7034 composite by accumulative orthogonal extrusion process

Abstract

The 7xxx aluminum matrix composites (AMC) with higher Zn content usually have attractively higher strength whereas the accompanied lower ductility limiting their wide application. In this study, an accumulative orthogonal extrusion process (AOEP) is proposed to improve the ductility of 7xxx AMC with higher Zn without sacrificing the strength. In the case of 8% wt. TiB2/AA7034 (11% wt. Zn) composite, it is shown that the material can reach an excellent combination of strength and ductility (yield stress >700 MPa; uniform elongation ∼ 6%). The mechanisms dominating the strength are qualitatively discussed by analyzing different strengthening mechanisms. The potential mechanism controlling the higher ductility is analyzed and discussed emphatically. Our results show that there are mainly two reasons leading to the higher ductility of the studied composite after AOEP (1) the decrease speed of work hardening rate (i.e. the dynamic recovery rate of dislocations): with the increase of deformation can be alleviated; (2) the inclusion-induced cracks can be effectively suppressed. Our results reveal that the prepared composites by coupling traditional casting and deformation can break through the strength-ductility trade-off of 7xxx AMC, which can provide the guidance for designing and preparing high-performance structural materials.