Evolution of flow stress in aluminium during ultra-high straining at elevated temperatures. Part II

Abstract

During torsional deformation of A1 (purity 99·7%) with 0·1 or 2mm grains at 400°C and 0·2s-1, the flow curve rises to a steady-state plateau of 18 MPa for ∊ = 0·5-3·0 and then gradually decreases by 27% by ∊ = 20, after which it remains constant at about 12°5 MPa. The decrease after the traditional steady-state regime results from the formation of a final texture mainly {112}<110>(111) which reduces the Taylor factor from 2·89 to 2·39. The subgrains remain equiaxed and constant in size from the first steady-state domain through the second. A final structure of subgrains with a third of their perimeters large-angle boundaries has the same flow stress as one with mainly dislocation walls.