Evolution, microhardness of ZrAlSi intermetallic and its impact on the elevated-temperature properties in Al–Si alloys

► Evolution of ZrAlSi intermetallics in Al–xSi–2Zr alloys was detected ► Microhardness of ZrAlSi intermetallics increases with Si content ► Al and Si atoms can replace each other to some extent in ZrAlSi phases ► Precipitation of ZrAlSi in an Al–Si piston alloy is bad for the elevated-temperature properties. The influence of Si addition on the microstructures and properties of ZrAlSi intermetallics in Al–xSi–2Zr alloys was investigated. With Si addition increasing from 3wt.% to 60%, ZrAlSi evolves from Zr(Al1−mSim)3 (0.10≤m≤0.21) to Zr(AlnSi1−n)2 (0.05≤n≤0.15), the content of Si in ZrAlSi and microhardness of the intermetallics increase synchronously. Besides, all the ZrAlSi intermetallics exhibit flake-like morphology. The effect of Zr addition and precipitation of ZrAlSi intermetallics on the elevated-temperature properties of an Al–Si piston alloy was investigated, and the tensile strength is increased by 3.8% with 0.11% Zr and decreased by 5.0% with 0.46% Zr addition, while the elongation and yield strength are increased by 13.0% and 6.9% with 0.11% Zr and decreased by 9.6% and 7.3% with 0.46% Zr addition, respectively.