Effect of Mn, Ni, and Zr Addition on the Tensile Properties and Precipitation Behavior of Sr-Modified Al–Si–Cu–Mg-Based Alloys

The current study is aimed to enhance the tensile performance of Al–Si–Cu–Mg cast alloys at both ambient and elevated temperatures. The investigation is focused on incorporating zirconium (Zr) as a primary alloying element, alongside nickel (Ni) and manganese (Mn), to assess their suitability for automotive engine applications. In Mn-containing alloys, tensile strength improvement was observed due to the precipitation of compacted α-Al₁₅(Fe, Mn)₃Si₂ and Al₆Mn phases. Meanwhile, Ni-bearing phases such as Al₃CuNi and Al₃Ni in Ni-containing alloys were found to inhibit crack propagation, thereby enhancing tensile properties. Results indicated that the addition of 0.75 wt.% Mn yielded comparable strength values to alloys containing 2–4 wt.% Ni at ambient temperature. Additionally, the presence of 0.25% Zr facilitated the precipitation of fine metastable L1₂-Al₃Zr particles, contributing to improved alloy strength. However, the introduction of 4% Ni resulted in the formation of Al–Cu–Ni particles rather than Al₂Cu, leading to a decrease in alloy strength upon aging.