Deformation Behavior of Inhomogeneous Layered Microstructure

Abstract

Multipass friction stir processing (FSP) technique was used to get inhomogeneous layered microstructure in Al 5086 alloy. Different proportions of fine and coarse grain microstructures were generated using FSP. In the present work, material with inhomogeneous layered microstructure generated using FSP was subjected to deformation at temperature of 500°C and at strain rate in the range of 5×10-4 to 1×10-2 s-1. It was observed that the inhomogeneous layered microstructure with more than 50% fine grain microstructure is required to get higher elongation to failure. However material having homogeneous fine grain microstructure showed lower elongation to failure than the material having both fine and coarse grain microstructures. By varying the proportion of fine and coarse grain microstructures higher ductility was obtained at higher strain rate as compared to a material with homogeneous microstructure. It is clear that materials with inhomogeneous microstructure are not following “rule of mixture” type of behaviour.

Effect of Grain Size on Superplastic Deformation of Metallic Materials

“…However in Al alloys, inhomogeneous microstructure has shown to exhibit higher ductility than homogeneous fine-grained microstructure [74][75][76]87]. Pancholi et al [90] demonstrated that at least 50% fine grain microstructure is required in the Al 5086 alloy for it to exhibit superior superplasticity when compared to the homogeneous fine-grained material. It was argued that microstructural refinement in the remaining 50% of coarse-grained microstructure, which leads to fully homogenous microstructure in the material, was the reason for higher superplasticity [84,87].…”