Grain refinement in an Al-Er alloy during accumulative continuous extrusion forming

The grain of an Al-0.2Er alloy (wt%) was refined by accumulative continuous extrusion forming (ACEF). Microstructure of the Al-Er alloy subjected to ACEF was investigated through electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The results revealed that the formation of ultra-fine grains results from a type of continuous dynamic recrystallization (CDRX) that is induced by large strains. With the accumulation of strain, LAGBs gradually introduced and transformed into HAGBs, which leads to an increase in the average orientation angle. The micro-grain alloy is refined through repeated passes of the continuous extrusion forming process and the average grain size of the Al-0.2Er (wt%) alloy decreased from 26.01 mu m to 1.3 mu m in four passes. The Al-0.2Er (wt%) alloy had a smaller average grain size than that of pure aluminum. The formation of precipitates in Al-Er alloy can stimulate the nucleation of CDRX by increasing the local strain energy and slow the growth of recrystallization grains by limiting grain boundary migration that causing grain refinement. (C) 2016 Elsevier B.V. All rights reserved.