Microstructure and texture evolution of Al-7075 alloy processed by equal channel angular pressing

Equal channel angular pressing is an effective technique to control the texture and microstructure of metals and alloys. Texture and microstructure of an Al-7075 alloy subjected to repetitive equal channel angular pressing through a 90° die were evaluated by X-ray diffractometer and orientation imaging microscopy. It is observed that processing through different routes leads to different types of textures, in both qualitative and quantitative senses. The texture calculation by Labotex software reveals that texture strengthens after the first pass and weakens by progressing ECAP process up to 4 passes. Microstructure investigations show that after 4 passes of equal channel angular pressing via routes BC and A, very fine grains with average grain size of about 700 nm and 1 μm appear, respectively, and most of the grains evolve into arrays of high angle boundaries. The effects of covering the Al-7075 billets with copper tube on texture and microstructure were also studied.

Damage prediction of 7025 aluminum alloy during equal-channel angular pressing

Equal-channel angular pressing （ECAP） is a prominent technique that imposes severe plastic deformation into materials to en- hance their mechanical properties. In this research, experimental and numerical approaches were utilized to investigate the mechanical prop- erties, strain behavior, and damage prediction of ECAPed 7025 aluminum alloy in various conditions, such as die channel angle, outer comer angle, and friction coefficient. Experimental results indicate that, after the first pass, the yield strength, ultimate tensile strength, and hardness magnitude are improved by approximately 95%, 28%, and 48.5%, respectively, compared with the annealed state, mainly due to grain re- finement during the deformation. Finite element analysis shows that the influence of die channel angle is more important than that of outer comer angle or friction coefficient on both the strain behavior and the damage prediction. Also, surface cracks are the main cause of damage during the ECAP process for every die channel angle except for 90°; however, the cracks initiated from the neighborhood of the central re- gions are the possible cause of damage in the ECAPed sample with the die channel angle of 90°.

Equal Channel Angular Pressing of Tubular Samples

A new technique to equal channel angular pressing of tubular samples has been proposed and investigated through experiments and simulations. Deformation behavior of copper tube sample was numerically analyzed during the first pass of tubular ECAP process. The investigation included the efect of various tube wall thicknesses on the efective strain magnitude and strain distribution uniformity. It is shown that tube wall thickness of 3.5 mm gives the optimum value for strain behavior. In addition, copper tube specimens with 3.5 mm wall thickness have been successfully ECAPed up to four passes with the die channel angle of 90 using flexible polyurethane rubber pad. Micro-hardness measurements on both annealed and ECAPed tubes show that 33% and 57% increases in hardness value and also, 50% and 70% reductions in the grain size were achieved after the first and fourth passes respectively. Furthermore, tube wall thickness measurements show that the process does not change the dimension of deformed specimens.