Effects of Scandium Content and Solution Process on Microstructure and Properties of Al-Zn-Mg-Cu-Sc-Zr Alloy

Al-Zn-Mg-Cu-Sc-Zr alloys with scandium mass fractions of 0.02%, 0.07% and 0.12% were designed. The effects of scandium content and solution temperature (450-490 ℃) and time (0.5-5 h) on the microstructure and properties of as-cast alloys were studied. The results show that with the increase of scandium content, the grains of the alloy were refined, but the coarse second phase content at grain boundaries increased; the hardness decreased. After solution at 470 ℃ for 1 h, the hardness of the alloy with 0.02wt% scandium was the highest. Continuously increasing the solution temperature or prolonging the solution time could lead to the increase of grain size, and prolonging the solution time could also lead to the aggregation of blocky second phases at the grain boundary; the hardness decreased.