ECAP으로 제조된 초미세립 5083 Al 합금의 동적 변형거동

Abstract

Dynamic deformation behavior of ultra-fine-grained aluminum alloys fabricated by equal channel angular pressing (ECAP) was investigated in this study. Dynamic torsional tests were conducted on four aluminum alloy using a torsional Kolsky bar, and then the test data were analyzed in relation to microstructures, tensile properties, and adiabatic shear band formation. The ECAP`ed specimens consisted of a considerable amount of second phase particles, which were refined and had an equiaxed shape as the ECAP pass number increased. The dynamic torsional test results indicated that maximum shear stress increased, while fracture shear strain remained constant, with increasing ECAP pass number. Observation of the deformed area beneath the fracture surface after the dynamic torsional test indicated that a number of voids initiated mainly at second phase particle/matrix interfaces, and that the number of voids increased with increasing pass number. Adiabatic shear bands of 100-150μm in width were formed in the as-extruded and 1-pass specimens having coarser second phase particles, while they were hardly formed in the 4-pass and 8-pass specimens having finer second phase particles. The possibility of the adiabatic shear band formation was explained by concepts of absorbed deformation energy and void initiation. (Received October 29, 2004)