It is known that grain refinement improves balance of strength and ductility of materials. As a technique to obtain fine-grained microstructure, dynamic recrystallization can be used in industrial processes. The authors reported that fine grains appear beneath the surface of Al-Mg alloy sheet by high-speed rolling. In this study, rolling conditions to form fine recrystallized microstructure were investigated. AA5052 alloy sheets were rolled at 500 m/min, 1000 m/min or 2000 m/min with thickness reduction of 30%, 50% or 70% at 473 K, 523 K, 573 K or 623 K. After the rolling, the sheets were water-quenched immediately. It is found that the critical strain for dynamic recrystallization is very large. For example, when the sheets are rolled at 1000 m/min and 623 K, thickness reduction greater than 76% is required for dynamic recrystallization.

In order to improve the accuracy of forming analysis for aluminum alloys, it is important to determine precise flow stress equation for aluminum alloys. In case of 5000 series aluminum alloys, formability is difficult to predict due to non-uniform deformation such as dynamic strain aging and stretcher-strain. To identify flow stress curve of A5182-O for wider strain range, the methods using rolling-tensile test and Vickers hardness test was investigated and compared with conventional regression curve obtained by uniaxial tensile test. The three methods were assessed in prediction of neck formation. It is found that stress-strain relationship without dynamic strain aging effect is required for precise prediction of uniform elongation. Plastic instability condition was predicted more precisely by either rolling-tensile test or Vickers hardness test than by conventional tensile test.