Deformation Behaviour and Fracture Mechanism of Ultrafine-Grained Aluminium Developed by Cryorolling

This chapter highlights the fundamental deformation and fracture mechanism of an engineered ultrafine-grained (UFG) material developed by a combination of cryorolling and short-annealing treatment. The UFG material developed by cryorolling possesses superlative tensile strength. However, the ductility and strain hardening potential of the material is found to be low, reducing its manufacturing capabilities. Controlled post-deformation annealing results in a combination of good strength and ductility. The anisotropic property of the material is also improved after short-term annealing. These properties have been attributed to the unique equiaxed, thermally stable microstructure comprising of high-angled nanometric grains. The various mechanical properties have been experimentally evaluated by performing the tensile test at all three different processing conditions (base, cryorolled, annealed) and the corresponding strain hardening potential, fracture behaviour and anisotropic properties have been systematically investigated. These properties have been correlated with the microstructural features of the material. This has been achieved by mechanical testing and characterisation of the material by employing transmission electron microscopy, fractographic analysis and determination of mechanical anisotropy coefficient (Lankford coefficient). Finally, a case study on the improved microforming abilities of UFG material over coarse-grained material has been presented.