Evaluating the influence of various routes on micro-structure and mechanical properties of AA-6063 after equal channel angular pressing

Abstract

One of the best suited methods for producing grain refinement in ductile metals is the equal channel angular pressing (ECAP) technique that can also preserve the dimensions of a rod-shaped specimen. This work used a modified die with a pair of studs for better alignment of the two die halves for ECAP cold-working of an aluminium alloy. The characterization of the Al 6063 alloy was done by optical microscopy, electron back scattered diffraction, fractographs (SEM), tensile testing and Vickers hardness testing. The micro-structural changes, homogeneity in grains, tensile strength and Vickers hardness has been studied after ECAP by the Routes A (sample is pressed exclusive of rotation between repeated passes), BA (sample is rotate by 90° in alternate directions) BC (sample is rotated by 90° in the same sense (clockwise/anticlockwise), and C (sample is rotated by 180°) at room temperature with modified die. The samples were examined after four, eight and ten passes. The die had a channel angle of 90° and an angle of curvature of 5°. Characterisation indicated that the grain size reduces after each passes and the microstructure improves. Initial passes show remarkable improvement in Vickers hardness and the later passes improve homogeneity. The initial core grains turn into ultra-fine grains. The results revealed that ultra-fine grains (UFG) development with improved mechanical properties is best obtained by using the route C than any of other three routes. Al alloy 6063 produced in this way can be greatly useful in aerospace and automobile industries due to its improved mechanical properties and bulk production facility.