Structural change of rapidly solidified 2024 aluminium alloy powders in mechanical milling and subsequent consolidation process

Rapidly solidified 2024 aluminium powders were mechanically milled, and then consolidated by vacuum hot-pressing and hot hydrostatic-extrusion. The grain-growth and phase-separation behaviors during the consolidation process were studied by X-ray diffraction and TEM observation. The results show that mechanical milling (MM) produces a supersaturated solid solution with a fine microstructure of nanometer-sized grains. In the consolidation process, the grain size increased, and Al2Cu and Al-2(Cu, Mg, Si, Fe, Mn) intermetallic-phases precipitated. A deformation-enhanced grain growth behavior was observed. Vacuum hot-pressing results in more obvious grain growth than simple annealing does, and hot hydrostatic-extrusion results in more serious grain-size coarsening than hot pressing does.