Effect of Cu particles on microstructure and mechanical properties of an AA6061-10Cu hybrid material fabricated by extrusion of powder blend

In this study, an AA6061 alloy with 10 vol.% Cu (AA061-10Cu) hybrid material was fabricated through hot extrusion of a compacted AA6061/Cu powder blend, followed by a tailored T6 heat treatment. The incorporation of Cu particles significantly promoted continuous dynamic recrystallization (CDRX) of the AA6061 matrix through the particle stimulated nucleation (PSN) mechanism and facilitated the diffusion of 2.25 wt.% Cu into the AA6061 matrix. The combined effects of CDRX and Cu diffusion led to a substantial reduction in grain size from 6.1 to 2.5 μm and an increase in the microhardness of the AA6061 matrix from 47 to 65 HV in the as-extruded AA6061-10Cu hybrid material. After the tailored T6 heat treatment, the microhardness of the AA6061 matrix further increased to 88 HV, which remained significantly higher than that of the AA6061 alloy subjected to the same treatment. The enhanced ultimate tensile strength of the hybrid material, compared to the AA6061 alloy, was attributed to grain boundary strengthening from matrix grain refinement, additional Orowan strengthening due to Al 2 Cu precipitates, and heterodeformation induced (HDI) hardening resulting from the hardnesses mismatch between Cu particles and the matrix. Consequently, the ultimate tensile strength of the hybrid material was markedly higher than that of the AA6061 alloy in both the as-extruded state (207 vs. 166 MPa) and the tailored T6 heat treated state (253 vs. 176 MPa).