Effect of nickel on the mechanical properties of spray-formed Al-15Si-2Cu alloy at elevated temperatures

In the present study, the effect of nickel (Ni) on the mechanical properties of spray-formed (SF) Al-15Si-2Cu alloy at different temperatures was examined and evaluated with that of the as-cast (AC) alloy. The microstructure of SF alloys revealed uniformly distributed spherical shaped primary silicon and eutectic silicon phases along with fine Ni and Cu intermetallic particles dispersed throughout the equiaxed Al matrix. The microstructure of AC alloys consisted of coarse primary Si, flake-type eutectic phase, Cu-rich intermetallics with a complex branched morphology and a network of short strips. The mechanical properties of the alloys were assessed at temperatures of 30°C, 100°C, 200°C and 300°C. The SF alloys exhibited higher hardness than AC alloys at all temperatures with a maximum increase of 74 % at 30°C. The hardness of alloys showed a decreasing trend with increasing temperature. The mechanical strength of SF alloys was higher than that of the AC alloys across the entire temperature range from 30°C to 300°C with a decrease in ultimate tensile strength (UTS) by 4–6 % at 250°C. The SF alloys demonstrated a significant increase in UTS (25 % at 30°C and 40 % at 300°C) compared to the AC alloys. The Al-15Si-2Cu-2Ni alloy showed highest increase (14.3–18.6 %) and Al-15Si-2Cu-6Ni alloy showed the lowest increase (10.5 % to 14 %) in percent elongation between 30°C and 300°C.