The influence of cooling rate on the microstructures and mechanical properties in ultrafine-grained aluminum processed by hot rolling

Commercially pure aluminum AA1050 was processed by hot rolling followed by subsequent water quenching (WQ) and furnace cooling (FC). The samples processed via these two approaches were then cold rolled to obtain ultrafine-grained (UFG) structures. Mechanical behavior studies showed that the WQ UFG Al exhibited a yield stress of 178 MPa and a total elongation of 5.3%, which are higher than those of the FC UFG Al (162 MPa and 3.1%, respectively). Microstructural analyses revealed that the origin of the high strength of the WQ UFG Al is attributable to smaller grain dimensions in the quenched and rolled material. The measured enhanced ductility was rationalized on the basis of three mechanisms: first, improved dislocation accumulation; second, a higher rate of strain hardening due to solid solution pinning during plastic deformation; and third, an increased proportion of high-angle grain boundaries.