Precipitation transformation and strengthening mechanism of droplet ejection lightweight medium-entropy AlZnMgCuLi alloy

Designing high-performance Al-based alloys on the basis of the entropy concept offers a promising strategy for next-generation advanced structural materials. In this work, a high-Zn-content lightweight medium -entropy AlZnMgCuLi alloy (0.35 cm3/g) is fabricated by droplet ejection. The effects of hot rolling, short -time solid solution treatment and peak ageing on microstructure and mechanical properties of the alloy are systematically studied. The results show that after hot rolling at 380 degrees C, the specific density is 0.31 cm3/g and elongated grains with the average size of 20 mu m are observed. Most of the secondary phases are dis-solved into the alpha(Al) matrix after short-time solid solution (450 degrees C, 20 min). An excellent ultimate tensile strength of 618 MPa is achieved after ageing treatment, which is considerably higher than that of the as -deposited alloy (234 MPa). Elongated grains, solid solubility, dislocations and a large number of ageing precipitates are beneficial to the high strength of the alloy. Such precipitates together with narrow precipitate free zones cause a brittle intergranular fracture. (C) 2022 Published by Elsevier B.V.