Effect of processing route on microstructure and texture development in equal channel angular extrusion of interstitial-free steel

Abstract

Microstructure and texture evolution in equal channel angular extrusion (ECAE) of interstitial-free (IF) steel is investigated for up to 4 passes via routes A, B A, B C and C. Observations by transmission electron microscopy reveal that the efficacy of grain refinement depends on both processing route and pass number. The preferred route is found to be route C after 2 passes but route B C after 4 passes. Quantitative analysis of the experimental textures shows the development of {1 1 0}〈 u v w〉 θ and { h k l}〈1 1 1〉 θ partial fiber textures in all routes, but the orientation distribution along these fibers is more uniform in routes A and C than B A and B C. The experimental textures are well predicted using a visco-plastic self-consistent model based on the simple shear assumption of ECAE deformation. Finite element (FE) analysis and further texture simulations using the FE-predicted deformation history suggest that imperfect strain reversal is a main factor for the prevalence of shear-type textures and elongated lamellar substructure observed after the even-numbered passes of route C.