41. Three Turn ECAP Processing of AA6061 Alloy: Microstructure and Mechanical Properties

A popular Severe Plastic Deformation (SPD) process known as Equal Channel Angular Pressing (ECAP), is envisaged as the best method for large volume and at low cost for obtaining UltraFine Grain (UFG) in bulk metals, due to its low pressing force requirement and the resulting low pressure on pressing tool (plunger) and die. High-strength semifinished products produced from ECAP have a high potential for application for the manufacture of fasteners for aircraft, components of aircraft fuselage, medical devices, sports equipment, and microsystems. The usefulness of experimental and FEM analysis in developing practical ECAP process with innovative dies is demonstrated. Practical problems faced during single turn ECAP experimentations are identified (i.e., labour intensive process, reduction in billet size, billet jamming, etc.) and remedies are suggested in this work. A Multi-turn (Three Turn) ECAP process to increase the process efficiency and for upscaling the procedure is developed. Microstructural results indicate that AA6061 aluminium billet processed through innovative Multi-Turn ECAP die after four repetitive passes show the significant reduction in average grain size i.e., 10 µm (Fresh billet) to 0.3 µm (Processed billet after 4 passes), and smaller grain size helps substantially to increase the yield strength and tensile strength.