Microstructure and mechanical properties of Be-Al and Be-Al-Sc alloys with various solidification rates

Abstract

Beryllium-aluminum (Be-Al) and scandium (Sc)-containing Be-Al alloys produced at various solidification rates of 100 K s−1, 102 K s−1, 103 K s−1 and 104 K s−1 were investigated in this work. High solidification rate resulted in grain refinement and mechanical reinforcement of Be. The addition of Sc modified the Be dendrites into equiaxed/cellular grains with further decreased grain size. The addition of Sc also caused the formation of intermetallic compound Be13Sc in all four alloys with different solidification rates and the Al3Sc phase which could only be generated during rapid solidification process. Be-Al-Sc alloy with the minimum Be grain size of 1.8 μm and the highest Vickers hardness of 98 was obtained through melt-spinning. The distribution of Sc-containing particles and microstructure of the melt-spun alloy depended on the undercooling of the melt. Moreover, the Be grains underwent the planar-front growth at high undercooling or the dendritic solidification ending up with larger grain size at lower undercooling. Importantly, the refined microstructure contributed more to mechanical reinforcement of the alloys than the alloying-induced effects.