Microstructure of Al-Si-Mg alloy processed by rotary-die equal channel angular pressing

New rotary-die ECAP (RD-ECAP) was applied to a commercial Al-Si-Mg (AC4C) alloy to improve the ductility, and the microstructural developments and mechanical properties of ECAPed specimens were investigated. The as-cast Al alloy was used after machining to a cylindrical shape. ECAP was performed at 543, 603 and 673 K. The microstructure changes of samples were examined. The Vickers microhardness was measured with respect to RD-ECAP passes and the tensile test was conducted to check the high-temperature ductility. The samples after ECAP showed very clean external surface without any edge cracking. The grain size was drastically decreased and saturated into 2-3 mum after six passes because the dynamic recovery occurred during the process. After 10 passes, a very homogenous microstructure was obtained. The longation of the alloy increased from 25% to 125% after 10 passes, and the m value was 0.21 after 20 passes. (C) 2002 Elsevier Science B.V. All rights reserved.