Novel twinned Al 3 Sc dendrites in as-casted Al–Sc alloy

Graphical abstract Al-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.