Five samples of Pb-Ca-Sn-Al alloy with different initial microstructures were processed in the same way including cold rolling with thickness reduction of 30% at the temperature of liquid nitrogen and then annealing at 270oC (0.9Tm) for 1 to 10 minutes. Electron back-scatter diffraction (EBSD) analyses indicated the initial microstructure which is at the end of primary recrystallization with a averaged grain size around 10 microns, a fair quantity of annealing twins and a random orientation can definitely result in a final grain boundary character distribution (GBCD) mainly composed of special boundaries (SBs) of which its fraction is higher than 75%, and the averaged SB cluster size exceeds 200 microns, implying the GBCD is optimized in satisfaction. However, the initial microstructures of partial recrystallization or full recrystallization but with coarser grain size are not good at producing high fraction SBs, whereas the initial microstructure of deformation with very strong textures is harmful to the formation of SBs in the processing of rolling followed by annealing. High resolution EBSD measurements revealed that the interactions between mobile incoherent ∑3 boundaries which were probably introduced by the continuous recrystallization from the distorted coherent ∑3 ones could be the formation mechanisms of the GBCD containing high fraction SBs.
