An investigation on the effects of equal channel angular pressing on the mixed-mode fracture toughness and mechanical properties of 6063 aluminium alloy

摘要

In this study, effects of equal channel angular pressing (ECAP) on the mixed-mode fracture toughness of Al-6063 were investigated. The ECAP process continued up to 5 passes without failure. Grain refinement was obvious after 5 passes of the ECAP process. The average grain size reduced from 45μm to less than 1μm, and textural studies shows aligning the grains in known directions. After 4 passes, yield and ultimate strengths increase respectively from 100 and 209 MPa to 300 and 375 MPa and reduction in elongation was also observed. The microhardness improved after the process. The fracture toughness for different orientations was measured. For pure mode I (opening mode), its value decreased after the first pass from 18.4 to 15.71 MPa√m; however, it increased to about 18.8 MPa√m after the fifth pass. For mixed-mode loading condition, different orientations were investigated. The results revealed different fracture toughness reductions after the first passes of the process for specimens with different orientations. The fracture surfaces were studied by using scanning electron microscope, and refined equiaxed dimples were observed after the ECAP process.