Microstructure and texture evolution of bcc and fcc metals subjected to equal channel angular extrusion

Abstract

Texture and microstructural evolution of interstitial-free (IF) steel and copper (Cu) subjected to room temperature equal channel angular extrusion for N = 1, 2 and 4 passes, route B C were compared. Both materials exhibit texture development similar to simple shear. Orientations of E {0 1 1}〈1 1 1〉 and D {1 1 2}〈1 1 1〉 type components are most prominent for IF-steel, while maximum intensities for A and A ¯ {1 1 1}〈1 1 0〉 components were found in Cu. Quantitative texture and difference indices indicate a general increase up to the second pass followed by a decrease at the end of four passes. Following each pass, the five most dominant orientations were used to quantify the change in Taylor factor estimate for simulated uniaxial tensile deformation along the three principal deformation directions. The results show approximately equivalent estimates for both materials after four passes and reflect increasing microstructural homogeneity after a full 360° revolution of the billet longitudinal axis. Transmission electron microscopy shows strongly aligned lamellar boundaries oriented along the major slip planes and directions of bcc and fcc structures. After four passes, the refined microstructure is characterised by an average subgrain size of ∼230 for IF-steel and ∼170 nm for Cu.