Achieving strength-ductility synergy in a novel Al-Mg-Zn-Cu-Si lightweight multi-component alloy via eutectic structure refinement

The development of lightweight multi-component alloys (MCAs) with good strength plasticity synergy faces a significant challenge, owing to the enormous number of potential component combinations, serious microstructure defects caused by poor castability, and the inefficiency of conventional empirical trial-and-error approaches. To surmount this challenge, we proposed an alloy design method, using the CALPHAD-based highthroughput calculation (HTC) to quickly identify compositions in Al(100_w-x-y-z)MgwZnxCuySiz MCAs over highdimensional composition space that can make alpha-Al and Mg2Si nucleate at the same time. Then successfully low-cost prepared large-sized MCA ingots with less segregation and porosity, and good performance according to the HTC screening results, and the calculated nucleation temperatures were in high agreement with the experimental values, with an error ranging within 0.5%. The granular eutectic Mg2Si phase exhibited exceptional uniformity and dispersion within the microstructure of the Al77Mg8Zn5Cu6Si4 alloy, with an average size of 1.8 mu m. Consequently, the as-cast Al77Mg8Zn5Cu6Si4 alloy displayed superior strength plasticity synergy at room temperature (RT), with the ultimate compressive strength reaching 706 MPa and the strain reaching 14.2%. This work demonstrates that the CALPHAD-based HTC approach provides an effective strategy for accelerating the design of lightweight MCAs with large-size and excellent mechanical properties.