Grain Boundary Character Distributions Of Cold Rolled And Annealed Pb Alloy After Solid Solution And Pre-Ageing Treatments

The grain boundary character distribution (GBCD) of Pb-Ca-Sn-Al alloy, which were cold rolled (CW) and annealed after solid solution and solid solution plus pre-ageing treatments, were investigated by means of electron back scatter diffraction ( EBSD) techniques. The results indicated that the GBCDs containing high fraction special boundaries ( SBs ) which sufficiently interrupt the connectivity of high angle boundary ( HAB ) networks were developed in the samples which were recrystallized followed by solid-solution and 30%CW+270℃/annealing treatments. The same results were observed in the specimens which were cast followed by solid-solution ( or solid-solution plus pre-ageing ) and 90%CW+270℃/annealing plus 30%CW+270℃/anealing treatments. However, the GBCD with low fraction SBs and the HAB networks not interrupted was produced in the samples which were recrystallized followed by solid-solution plus pre-ageing and 30%CW+270℃/annealing treatment. Additionally, the SB fractions in the samples, which were recrystallized or cast followed by solid solution and subsequent cold rolling and annealing treatment, fall sharply as the holding time of final annealing at 270℃prolonged from 5min to 20min, but the same phenomenon were not appeared in the specimens pre-aged. Further discussion pointed out, owing to the precipitation and re-dissolution of Ca and Sn during pre-ageing and subsequent annealing, the change of stacking fault energy and the pinning effect of second phase particles on grain boundary migration may account for the results mentioned above...