Large UFG Al alloy plates from cryomilling

To assess potential routes for the production of high-strength Al 5083, gas-atomized powder was cryogenically ball-milled, to obtain a nanocrystalline structure, then hot vacuum degassed and consolidated by two methods: (1) hot isostatic pressing (HIPping) and extrusion, and (2) two-step quasi-isostatic (QI) forging. The consolidated billet in both cases was hot-rolled to produce 19 mm plate. Despite grain growth and differences in the consolidation and deformation processing, a similar, ultra-fine grained microstructure was obtained in both plates, with elongated grains predominantly in the range 100–500 nm. The cryomilled plates had similar tensile strengths in the plane of the plate, which were up to 60% greater than conventionally processed and work-hardened Al 5083. However, the QI-forged plate had significantly higher fracture toughness than the HIP/extruded plate, which was brittle for crack surfaces in the plane of the plate. The disparity in toughness values was attributed to differences in the prior powder particle boundary structure.