EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

The development of high entropy alloys (HEAs) and compositionally complex alloys (CCAs) have broadened the possibilities of alloy design by exploring wider regions of solid solubility. With an ever-increasing demand for high performance light weight alloys, the concepts developed within HEAs/CCAs is implemented into the design approach to alloys akin to the extensively used A357 alloy. Developing an alloy with an increase in the thermal stability or specific strength will give reductions in emissions within the transportation sectors, particularly within the aerospace industry. By utilising high throughput screening techniques, using the Al and HEA databases developed by Thermo-Calc, the solubility limit of elements currently used in Al-Si alloys is closely examined, as well as all available elements within the databases is further explored. Elements that were predicted to exhibit solid solubility with an Al-7Si (wt.%) alloy without precipitating additional phases was identified. A selection of alloys was designed and produced via conventional resistive heating, gravity casting and subsequent directional solidification containing varying additions of Mg, Zn, Ag, Li, Ga and Ti. The new alloys were microstructurally and mechanically characterised through SEM, EBSD, DSC, hardness and tensile testing at room and elevated (up to 200°C) temperatures. The newly developed alloys exhibited an increase in yield strength (up to 31%) over the base A357 at room temperature, and an improvement in ductility (up to 47%) at 200°C while still increasing the yield and tensile strength, without the introduction of new phases.