Effect of ECAP on microstructure and mechanical properties of a commercial 6061 Al alloy produced by powder metallurgy

Abstract

The 6061 (Al–1.01 wt% Mg–1.07 wt% Si) Al alloy was fabricated by powder metallurgy, and then subjected to equal channel angular pressing. The microstructure and mechanical properties such as microhardness and tensile properties of the equal channel angular pressed P/M 6061 Al alloy were investigated. The P/M 6061 Al alloy had an initial grain size of approximately 20 μm. After two pressings at 373 K using route A, the sample revealed microstructure of subgrain bands with a length of ∼0.8 μm and a width of ∼0.3 μm. The subgrain bands became larger above 1 μm in length and width after two pressings at 573 K. An equiaxed ultra-fine grained structure with the mean grain size of ∼0.5 μm was obtained after four repetitive equal channel angular pressings at 473 K using route A and C. The microhardness of P/M 6061 Al alloys was drastically increased from about 40 to 80 Hv by two repetitive pressings at 373 K. However, the microhardness decreased with increasing the pressing temperature. The tensile strength of 6061Al alloy before the equal channel angular pressing was 95 MPa, whereas it increased to both 248 MPa after two pressings at 373 K and 130 MPa after four pressings at 473 K, which was superior to that of a commercial 6061-O Al alloy.