An analysis of microband orientation in a commercial purity aluminium alloy subjected to forward and reverse torsion using Electron Backscatter Diffraction (EBSD)

Abstract

SummaryHigh-resolution electron backscatter diffraction has been used to study the effects of strain reversal on the evolution of microbands in commercial purity aluminium alloy AA1200. Deformation was carried out using two equal steps of forward/ forward or forward/reverse torsion at a temperature of 300 ° C and strain rate of 1 s − 1 to a total equivalent tensile strain of 0.5. In both cases, microbands were found in the majority of grains examined with many having microband walls with more than one orientation. For the forward/forward condition, the microband clusters were centred around − 20 ° and + 45 ° to the equivalent tensile stress axis, whereas for material subjected to a strain reversal, the clusters were at − 65 ° and − 45 ° . There was no evidence of microbands that were formed in the forward deformation step in the reversed material, which would suggest that a strain of 0.25 is sufficient to dissolve any microstructure history generated by the first step. Furthermore, the microbands within the strain-reversed material had a reduction in misorientation compared with the lineally strained material, suggesting that these microbands only formed at the onset of the second deformation step. This confirms that microband formation is complex and sensitive to strain path; however, it is still unclear to what extent microband formation is dependent on strain path history compared with the instantaneous deformation mode.

An Analysis of Deformation Microstructure and Subsequent Recrystallisation in Hot Deformed Aluminium Alloy AA5052 Using Forward and Reverse Torsion

“…The results presented above have shown that a linear (F/F) torsion test in hot deformed AA5052 produces a strong macroscopic directionality in the microbands formed. The data presented here also corresponds nearly exactly with the data of Lopez-Pedrosa et al [8] for AA1200 deformed at the same temperature to the same strain and the data of Hughes and Hansen [9], for room temperature deformed nickel deformed to slightly lower strain levels. This would suggest that like other deformation modes the microband angle distribution for torsion is very similar for both hot and cold deformation and materials of similar stacking fault energy.…”

Orientation dependence of the deformation microstructure in compressed aluminum

“…After reversal of the strain path in tension/compression tests [10], as well as in reversed torsion tests [11], the distribution of dislocation boundary inclination angles resembles a superposition of the distributions observed before and after the strain path reversal.…”

Evaluation of intragranular misorientation parameters measured by EBSD in a hot worked austenitic stainless steel

“…The apparent contradictory results for local parameters (stagnation) and OS (increase) from a strain of 0.4–0.5 could be associated to the omission of an analysis of the low misorientation axis. Indeed, the progressive alignment of the low misorientation axis with strain according to some external direction (Cizek et al ., 2005; López‐Pedrosa et al ., 2006) could lead to a more efficient way of accumulating misorientation with distance.…”