Novel twinned Al3Sc dendrites in as-casted Al-Sc alloy

Graphical abstractAl-Sc alloys with high Sc contents are served as sputtering targets for making high performance piezoelectric devices. The microstructure of these alloys would affect the sputtering process and the final quality of the functional devices. In this study, the microstructure in as-casted Al-20%Sc (atomic fraction) alloys is characterized and the feathery Al3Sc grains with twin relationships are reported for the first time. The crystallographic features of twined structures and growth directions are quantitatively analysed by electron backscatter diffraction (EBSD) technique. The twinning plane is parallel to {111} planes and growth direction is along <110> directions in Al3Sc. In addition, the twinned structures are affected by both the Sc content and cooling rate. The twinned grains are found in the alloy with high Sc content rather than lower alloyed samples and the density of the twin boundaries increases with increasing the cooling rate due to the refinement of the microstructure.

Automated summary

Al-Sc alloys with high Sc contents were found to exhibit feathery Al3Sc grains with twin relationships. The microstructure of these alloys has significant effects on the sputtering process and the quality of functional devices. Through quantitative analysis using electron backscatter diffraction (EBSD) technique, it was revealed that the twinning plane is parallel to {111} planes and growth direction is along <110> directions in Al3Sc. The occurrence of twinned structures is influenced by both the Sc content and cooling rate, with higher Sc content and faster cooling rates leading to higher density of twin boundaries.