Hot working of AA1050—relating the microstructural and textural developments

Abstract

An aluminum alloy AA1050 was deformed in plain strain at different hot working conditions. An increase in temperature or a decrease in strain rate reduced the relative drop in cube {001}〈100〉 and the relative increase in rolling texture components of Cu {112}〈111〉 and S {231}〈346〉, especially apparent at the higher strain. Along with such textural changes, significant differences in hot worked microstructures were observed. The two distinct microstructural features, as observed by polarized light optical microscopy, were grain boundary serrations (GBS) and in-grain inclined lines (IIL), typically observed at an approximate angle of 35° with rolling direction (RD). At higher temperatures and lower strain rates, and correspondingly lower Zener–Holloman factors ( Z≈10 9−10 10 s −1), coarse but nearly equiaxed grain interior substructures and GBS were observed. Interestingly, orientation imaging microscopy (OIM) clearly showed insignificant/non-noticeable differences between the substructures of different orientation components. An increase in Z aligned the grain-interior low angle boundaries at an angle of approximately 35° with RD and at higher Z ( Z≈10 12−10 13 s −1) the main microstructural feature was the IILs. Development of in-grain long range misorientation (LRM) was estimated to be the mechanism behind the optical visibility of the IILs. The appearance of IILs had two apparent effects—first the substructures of different orientation components were different, and secondly the stability of cube grains dropped noticeably. Generalizing the IILs or 35° inclined cell walls as plastic instabilities or strain localizations, the observed differences in their relative appearance at different deformation conditions and/or texture components could be explained. When formation of such strain localizations are considered as “necessary” for the reorientation of grain segment(s), the cube stability at low Z deformation could also be understood.