Effect of Cryo-Deformation on Aging Characteristics of Age-Hardenable Aluminium Alloys

The effect of plastic deformation by cryo-rolling on the microstructural evolution and aging characteristics of an Al-Zn-Mg alloy was investigated employing DSC, hardness measurements and TEM/EDAX. Specimens were water quenched after a solution heat-treatment, cryo-rolled upto - 90% deformation, short annealed and aged in 3 different temper conditions. The specimens aged under T6 condition have attained peak hardness with faster precipitation kinetics, during the second step of aging, i.e. at 150oC with in 1 to 3h, the time required being inversely proportional to the amount of deformation. The microstructure consisted of ultra-fine grains with size ranging between 100-250nm. This also resulted in finer precipitates of strengthening particles.