Processing Map for Hot Working of 7075Al/20%SiC (5 μm) Particulate Reinforced Metal Matrix Composites

The hot deformation behaviour of 7075Al/20%SiC (5μm) particulate reinforced metal matrix composites was studied by using processing map technique. The map has been interpreted in terms of the microstructural processes occurring in situ with deformation, based on the values of a dimensionless parameter (η) which is an efficiency index of energy dissipation through microstructural processes. An instability criterion has also been applied to demarcate the flow instability regions in the processing map using another parameter (ξ). Both the parameters (η and ξ) were computed from the experimental data generated by compression tests conducted at various temperature and strain rate combinations over the hot working range (300-500°C and 0.001-1 s-1) of the present material. The processing map exhibits two distinct η domains without any unstable flow conditions under the investigated temperature and strain rate conditions. The dominant microstructural mechanisms corresponding to these domains were identified to be extended dynamic recrystallization and flow localization. The 'stable' and 'unstable' regions in the processing maps were identified and compared with the reported microstructural observations of the deformed compression specimens. The optimum hot working conditions for these composites are suggested.