Structural analysis, mechanical and damping behaviour of Al-Zn based composites reinforced with Cu and SiC particles

The structural characteristics, mechanical and damping properties of stir-cast Al-10 wt.% Zn based composites developed using 6 and 8 wt.% Cu, and 8 wt.% SiC particles as reinforcements, were investigated. The low porosity (<4%), near absence of dissolved Cu in the Al-Zn matrix, and marginal presence of melt reaction-induced intermetallic phases, attest to the soundness of the castings. Besides hardness, the strength parameters - ultimate tensile strength (149.33 MPa and 138.64 MPa) and specific strength (54.3 MPa cm3 g-1 and 51.16 MPa cm3 g-1) - of the Al-Zn composites reinforced with 6 and 8 wt.% Cu, were superior to that of the unreinforced Al-Zn alloy (103.47 MPa) and the 8 wt.% SiC reinforced composite (130.5 MPa). The fracture toughness (17.32 MPa m1/2 and 13.66 MPa m1/2) and percentage elongation (15% and 12.5%) of the 6 and 8 wt.% Cu reinforced Al-Zn composites, also surpassed that reinforced with SiC (KIC - 12.28 MPa m1/2; % ϵf - 9.5%). Improved matrix/particles interphase bonding and the inherent ductile and tough nature of Cu over SiC, were cited responsible for the improved strength-ductility-toughness balance of the Al-Zn/Cu composites over that reinforced with SiC. The damping properties were generally temperature sensitive, with all compositions exhibiting increase in damping capacity at test temperatures 100-200 °C.