Advancements in High-temperature Cast Aluminum Alloys

Enhancing heat resistance in cast aluminum alloys is crucial for their efficient application in high temperatures. The challenge is in identifying the appropriate eutectic system that provides exceptional castability while simultaneously demonstrating high strength and thermal stability after solidification. Recent studies have been conducted on the Al-Ni eutectic system as a potential substitute for high-temperature use. Its good castability and low hot-tear tendency make it suitable for conventional casting. The Al-Ni alloy consists of a finely structured Al₃Ni eutectic with a rod-like morphology, exhibiting notable chemical stability and exceptional thermal characteristics that maintain performance up to temperatures of 500 °C. The enhancement of coherent L1₂-ordered nanoprecipitates within the α-Al matrix is expected to improve the high-temperature strength of Al-Ni cast alloys. Additions of Sc or Zr to the Al-Ni alloy could result in the formation of Al₃Sc and Al₃Zr L1₂-nanoprecipitates, respectively. Such nanoprecipitates exhibit exceptional excellent thermal stability and coarsening resistance due to the low diffusivity of scandium and zirconium in aluminum. Better coarsening- and creep resistance are achieved when Sc and Zr are added together, forming coherent Al₃(Sc,Zr) nanoprecipitates within the α-Al matrix between Al₃Ni microfibers, providing significant precipitation strengthening. Hence, this particular alloy has promising characteristics, positioning it as a viable candidate for use as a novel cast aluminum alloy in demanding industrial applications.