Effect of pre-heating on the microstructural evolution and super-plasticity of Al deformed by accumulative roll bonding
Ultrafine-grained AA1050 sheets have been produced by accumulative roll bonding (ARB). Two ARB processes have been compared in this study, one with preheating and the other without. In the preheated process the specimens were heated at 2508C for 3 minutes before ARB rolling. The microstructures of the ARB specimens were then investigated by transmission-electron-microscope (TEM) at different positions along the thickness, and it is found that the specimens deformed by ARB generally present a strong rolling texture with elongated grains in the middle of the sheet and roughly equiaxed grains near the surface. However, the equi-axed grains near the surface of the deformed sample had been impaired to some extent by preheating, and there was less grain refinement and more in-grain dislocations in the preheated specimens. A super-plasticity test was conducted on an Instron-type machine, with the results showing that pre-heating had improved superplasticity to a certain extent.