High strength and large ductility of a fine-grained Al-Mg alloy processed by high strain rate hot rolling and cold rolling

摘要

Achieving high strength and large ductility simultaneously has been a long-standing goal in Al alloy. In the present study, a superior combination of ultimate strength (354 ± 1 MPa) and elongation (34 ± 0.9%) are achieved in a fine-grained (4.7 μm) Al-6.5 Mg alloy prepared by high strain rate hot rolling (HSRR) at 400 °C. The ultimate strength can be further improved to 454 ± 2 MPa after the subsequent cold rolling (CR), accompanied by an acceptable good ductility of 9.2 ± 1.1%. The microstructural evolution is characterized by electron backscattered diffraction (EBSD), transmission electron microscopy (TEM) and X-ray diffraction (XRD). It has been shown that the high ductility of HSRRed alloy is attributed primarily to the high content of solute Mg atoms, high fraction of fine grains with high-angle grain boundaries (HAGBs) and the weak texture, while the high strength is mainly due to the combination strengthening effect from strain hardening, grain refinement and high content of solute Mg atoms. This study provides a possible strategy to gain high strength and large ductility, i.e. obtaining fine grains by enhanced recrystallization resulted from high strain rate and high content of solute Mg atoms, and then followed by cold working hardening.