Combined Effect of Particle Reinforcement and T6 Heat Treatment on the Compressive Deformation Behavior of an A357 Aluminum Alloy at Room Temperature and at 350 °C

Abstract

Solid state sintering of cast aluminum powders by resistance heating sintering (RHS), also known as spark plasma sintering or field-assisted sintering technique, creates a very fine microstructure in the bulk material. This leads to high performance material properties with an improved strength and ductility compared to conventional production routes of the same alloys. In this study, the mechanical behavior of an RHS-sintered age-hardenable A357 (AlSi7Mg0.6) cast alloy and a SiCp/A357 aluminum matrix composite (AMC) was investigated. Aiming for high strength and good wear behavior in tribological applications, the AMC was reinforced with a high particle content (35 vol.%) of a coarse particle fraction (d50 = 21 µm). Afterwards, separated and combined effects of particle reinforcement and heat treatment were studied under compressive load both at room temperature and at 350 °C. At room temperature compression, the strengthening effect of precipitation hardening was about twice as high as that for the particle reinforcement, despite the high particle content. At elevated temperatures, the compressive deformation behavior was characterized by simultaneously occurring temperature-activated recovery, recrystallisation and precipitation processes. The occurrence and interaction of these processes was significantly affected by the initial material condition. Moreover, a rearrangement of the SiC reinforcement particles was detected after hot deformation. This rearrangement lead to a homogenized dispersion of the reinforcement phase without considerable particle fragmentation, which offers the potential for secondary thermo-mechanical processing of highly reinforced AMCs.

Keywords

• aluminum cast alloy
• AMC
• compression
• field-assisted sintering
• heat treatment
• hot deformation