Comparison of microstructures and strengths of an Al–2.5Mg alloy subjected to severe plastic deformation at room and liquid nitrogen temperatures

This work compares microstructural and strength properties of ultra-fine grained Al–2.5Mg alloy produced by multi-axial forging in a channel die at room and liquid nitrogen temperatures. The two ultra-fine grained microstructures after total equivalent strain of 2.3 exhibited similar grain sizes and orientation spread but significantly different respective strengths at room temperature. The difference in the strengths has been attributed to the higher dislocation densities in samples pressed at liquid nitrogen temperature. Dislocation densities were measured on the basis of average misorientations within grains measured using electron-back scattered diffractions.