Change in intragranular misorientation during stress relaxation in Al-Cu-Mg-Mn alloy subjected to continuous cyclic bending

Abstract

Change in intragranular misorientation during stress relaxation in Al-Cu-Mg-Mn (2024) alloy sheet subjected to continuous cyclic bending (CCB) has been investigated by electron back scatter diffraction (EBSD) technique. EBSD analysis revealed that kernel average misorientation (KAM) value was heitened not only in the sheet worked by CCB but also during stress relaxation test. Grain orientation spread (GOS) value, another misorientation parameter, was also calculated and compared with KAM value of each sample. Both of KAM and GOS values varied with four stages about stress and stored strain: (a) unloaded before stress relaxation test (SRT), (b) loaded before SRT, (c) loaded after SRT and (d) unloaded after SRT. Change in KAM value was likely corresponding to sum of applied and residual stresses. Quantitative relationship between increase and decrease in KAM value between the stages was divided into two types according to dynamic restoration mechanisms.