【作者】 张欣；

【导师】 王卫国；

【作者基本信息】 山东理工大学 ， 材料加工工程， 2007， 硕士

【摘要】 利用场发射扫描电子显微技术(FESEM)和电子背散射衍射(EBSD)技术研究了固溶和预时效对再结晶态和铸态Pb-Ca-Sn-Al合金冷轧退火后晶界特征分布(GBCD)的影响。结果表明:再结晶态Pb-Ca-Sn-Al合金固溶处理后直接进行30%冷轧变形和270℃/5min退火处理,∑3和(∑9+∑27)等特殊晶界比例分别达到49.6%和7.2%,特殊晶界较好地阻断了一般大角度晶界网络的连通性;相反,固溶处理后先进行预时效处理,然后再进行相同冷轧退火则形成较少的特殊晶界,∑3和(∑9+∑27)晶界的比例分别低于35.9%和2.5%,一般大角度晶界网络的连通性没有被阻断。这一结果与Ca和Sn的析出造成预时效样品基体层错能被抬高有关。铸态Pb-Ca-Sn-Al合金固溶处理后直接进行、以及固溶处理后先施行预时效处理然后再进行90%CW+270℃退火和30%CW+270℃/5min退火处理的样品,其GBCD差异不大,各样品中∑3和(∑9+∑27)晶界比例均分别达到55%和10%左右,一般大角度晶界网络被阻断的程度很好。其原因可能是预时效样品在90%CW+270℃退火处理过程中部分Ca和Sn重新溶入基体,并导致其层错能与固溶处理样品比较接近。不论是再结晶态还是铸态Pb-Ca-Sn-Al合金经固溶处理后直接进行冷轧退火,其特殊晶界比例在270℃/5min退火处理基础上随退火时间的延长急剧下降,而固溶后先进行预时效,其GBCD则基本不随退火时间延长而改变。这一现象可归因于预时效样品中Ca和Sn的析出所形成的第二相粒子对晶界的迁移起到了明显的钉扎作用。更多还原

【Abstract】 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更多还原