Microstructure and mechanical properties variations of pure aluminum subjected to one pass of ECAP-Conform process

Abstract

Aluminum rod (AA1100) is severely plastic-deformed by one pass of the ECAP-Conform method. Optical and electron backscatter diffraction (EBSD) methods are used for microstructural characterizations. EBSD examinations of in process and processed samples reveal that grain sizes are not changed appreciably and they are mostly elongated by the plastic deformation. The EBSD data shows an increase in the number of subgrains and inhomogeneous dislocation distributions. Estimation of the geometrically necessary dislocation (GND) densities is done by using EBSD data. Estimated average GND density of the annealed material is as low as 5 × 107 m−2. For severely deformed Al specimen, the estimated GNDs and SSDs densities are 2.9 × 1014 m−2 and 4.6 × 1014 m−2 respectively with an averaged total dislocation density of 7.5 × 1014 m−2. Mechanical properties of samples at different stages of deformation are examined through hardness and tensile tests. Microhardness results show the inhomogeneous distribution of hardness at these sections due to the complex and varied loading conditions. Despite hardness inhomogeneity, macro tensile test results show that ECAP-Conform process is very effective in increasing the strength of the material at least by the factor of three. This increase in strength can be well interpreted by an increase in dislocation densities and formation of subgrains.