Superior Strength-Plasticity Achievement in Recycled Al-Si Alloy Through Intercritical Rolling

Abstract

ADC12 aluminum alloy is widely used in the automotive and electronics fields due to its excellent castability and recyclability. However, its coarse silicon phases and inhomogeneous microstructure severely limit its mechanical properties. In this study, hot rolling within the two-phase region (520–560 °C) was applied to systematically investigate the synergistic effect of rolling temperature on the microstructure and mechanical properties of ADC12 alloy. Through three-dimensional phase morphology characterization and mechanical tests, the optimal rolling temperature was identified as 540 °C. At this temperature, the eutectic Si phases fragments into short rods, with their interconnectivity significantly reduced. The α-Fe phase exhibited rounded and passivated edges, while the Al₂Cu phase dispersed as fine precipitates. Following rolling, the alloy exhibited substantial enhancements in comprehensive properties: tensile strength reached 348.41 MPa (an increase of 101.96%), elongation reached 6.40% (an increase of 193.57%), and the strength-ductility product reached 2.229 GPa% (an increase of 486.57%). The fracture mode transitioned from brittle intergranular to a ductile-brittle mixed type. Subsequent T6 heat treatment further increased the yield strength by 333.4% and elongation by 37.5%. Mechanistic analysis shows that the synergistic effect between the high-temperature liquid phase and rolling-induced shear stress underpins the property improvement: the liquid phase promotes atomic diffusion and phase reconstruction, whereas the rolling force disrupts the hard and brittle phase network, alleviates stress concentration, and optimizes phase distribution.This work provides a theoretical foundation and technological framework for efficient plastic processing and performance optimization of recycled aluminum alloys.