Influence of annealing on stain hardening behaviour and fracture properties of a cryorolled Al 2014 alloy

The influence of annealing on strength, ductility, strain hardening, plastic instability and fracture behaviour are studied in the present work on a cryorolled Al 2014 alloy by tensile test, transmission electron microscopy, macrograph analysis and fractography study. Investigations on the cryorolled alloy have been done for different annealing temperatures in the range of 100-400 °C and the results obtained are correlated with the microstructural evolution, precipitation behaviour and post failure analysis. Study reveals a complex trend in ductility and strain hardening behaviour as a result of simultaneous occurrence of dislocation annihilation, recrystallization and precipitation evolution during annealing. By investigations of fractured samples, dominant mode of fracture is found to be shear deformation and upon annealing the fracture mechanism is affected jointly by propagation of microvoids and shear deformation due to combined action of precipitation and microstructural evolution. Yield strength is increased by 4 times after cryorolling and retained after annealing up to 100 °C. It even remains higher than the base material up to 350 °C, due to the combined effect of precipitation hardening and thermal stability of microstructure.