Superplasticity of Al-Mg-Li alloy prepared by thermomechanical processing

Grain refinement of Al-Mg-Li alloys for superplasticity prepared by thermomechanical processing has been a difficult task due to the cracking of these alloys when rolled at low temperatures. Raising the rolling temperature resulted in enhanced rollability of these sheets with no cracks but very coarse grains after recrystallisation. To solve this problem, a cross rolling schedule was developed to hinder fracture and simultaneously provide enough stored energy for following recrystallisaiton coupled by lowering the reheating temperature. Fine, equiaxed grains of ∼7 μm was achieved by this new approach and maximum total elongation of about 915% was obtained when deformed at a temperature of 525°C and an initial strain rate of 1×10 −3 s −1 .