Factors influencing creep flow and ductility in ultrafine-grained metals

The creep behaviour of high purity aluminium and copper and their Al–0.2 wt%Sc and Cu–0.2 wt%Zr alloys was examined after processing by equal-channel angular pressing (ECAP) with an emphasis on creep ductility and the ECAP microstructural homogeneity. It was found that, under the same loading conditions, the creep ductility of the ultrafine-grained materials processed by ECAP continually increases with increasing numbers of ECAP passes. A detailed quantitative microstructural study was conducted using the electron backscatter diffraction (EBSD) methods. This analysis revealed that, with increasing numbers of ECAP passes, the mutual misorientation of neighbouring subgrains grows and the subgrains continuously transform to grains having high-angle grain boundaries.