MICROSTRUCTURAL EVOLUTION AND TENSILE PROPERTIES OF AN ULTRAFINE-GRAINED AL-MN ALLOY PROCESSED BY EQUAL CHANNEL ANGULAR EXTRUSION

The microstructure and tensile properties of an Al-Mn alloy (AA3003) processed by equal channel angular extrusion (ECAE) were investigated. After being processed to an equivalent strain of similar to 8, the grain size was 450 nm and it was reduced to 390 nm after deformed to a strain of similar to 13. Tensile tests indicated that the tensile strength increased as the being accumulated strain imposed on the alloy increased from similar to 8 to similar to 13, while the tensile elongation remained nearly unchanged (0.09). The strain rate sensitivity (SRS) of the ultrafine-grained (UFG) Al-Mn alloy increases with increasing the accumulated strain imposed on it. A low temperature (743 K) homogenization was applied to produce a structure having large amount of fine dispersoids and less Mn in solution. After being plastically deformed to a strain of similar to 8, the low temperature homogenized material exhibited a higher tensile strength and a larger SRS value as compared to the high temperature (873 K) homogenized counterpart. As the strain rate decreased from 1x10(-4)s(-1) to 1x10(-5)s(-1), the low temperature homogenized material showed a considerable improvement in tensile ductility, which might be related to the high SRS value.