Effect of cooling rate on microstructure and mechanical properties of rapidly solidified Al-based bulk alloys

The microstructure and mechanical properties of Al₈₆Si _0.5Ni_4.06Co_2.94Y₆Sc_0.5 alloys produced by copper mold casting at different cooling rates were investigated. With decreasing the cooling rate during solidification, the microstructure for these rapidly solidified alloys varied from almost fully amorphous for 1-mm-diameter rod to chill-zone surface layered structures for 1.5-mm- and 2-mm-diameter ones. Compared to the 1-mm-diameter alloy rod formed at a faster cooling rate, the 1.5-mm- and 2-mm-diameter alloys possess lower strength, whereas larger compressive plasticity due to the formation of composite structure with soft inner core and hard chill-zone outer shell. The results indicate that the mechanical properties of the rapidly solidified Al-based bulk alloys can be tunable by employing proper cooling rate.