摘要
{111}/{111}近奇异晶界比一般晶界更耐蚀,研究此类晶界的形成条件、影响因素和生成机制,设法调控此类晶界并提高其比例是改善相关铝合金晶界间耐腐蚀性能的根本途径。为了解铝合金生成{111}/{111}近奇异晶界的本征行为,本工作选择高纯Al(99.99%)为实验材料,首先经室温反复多向锻造和370℃再结晶退火获得晶粒尺寸均匀(平均晶粒尺寸约为20μm)且晶粒取向随机分布的组织均匀化初始样品;再将初始样品分别在室温(25℃)和-196℃深冷条件下进行厚度减缩量为80%的轧制变形,及370℃、30 min再结晶退火处理。采用EBSD和基于五参数分析的晶界界面匹配定量表征方法对2种样品进行测试和分析。结果表明,经-196℃深冷轧制并再结晶的样品,其{111}/{111}近奇异晶界比例达到6.0%,相比室温轧制并再结晶的样品提升了122%。XRD、EBSD及硬度测试结果表明,经室温和-196℃深冷轧制的样品中均形成了较强的{011}<111ˉ>形变织构;相比于室温轧制,经-196℃深冷轧制的样品内残余压应力更大,晶粒碎化更严重、储能更高。在后续370℃退火过程中,经室温和-196℃深冷轧制的样品,其再结晶机制均以{011}<011ˉ>取向生长为主;相比于室温轧制,经-196℃深冷轧制的样品可提供更大的晶界迁移驱动力,其样品再结晶组织的平均晶粒尺寸更大且{011}<011ˉ>再结晶织构更强。统计结果表明,{011}<011ˉ>取向晶粒与其他取向的晶粒毗连所形成的晶界中存在较高比例的{111}/{111}近奇异晶界;同时,{011}<011ˉ>取向晶粒与其相邻的且具有{011}<011ˉ>漫散取向的晶粒间也形成较多的{111}/{111}近奇异晶界,这是导致经-196℃深冷轧制及再结晶的样品中{111}/{111}近奇异晶界比例较高的主要原因。
Recent advancements in grain boundary engineering have revealed that the{111}/{111}near singular boundary(NSB)exhibits superior resistance to corrosion attacks than the random boundary in aluminum and its alloys.Thus,understanding the influential factors and formation mechanisms of the{111}/{111}NSB,as well as regulating such boundaries,is crucial for enhancing the resistance perfor-mance of aluminum and its alloys against intergranular corrosion attacks.To intrinsically comprehend the formation mechanism of the{111}/{111}NSB in aluminum alloys,this study used high purity aluminum(99.99%)as the experimental material.Initially,the starting samples were synthesized through multidirec-tional forging at room temperature(25 ℃),followed by recrystallization annealing at 370 ℃.The as-synthesized starting samples exhibited uniform microstructures with an average grain size of 20μm and random grain orientations.Subsequently,two parallel starting samples were rolled at 25 ℃ and at the cryogenic temperature(-196 ℃),respectively,with an 80%thickness reduction,followed by immediate recrystallization annealing at 370 ℃ for 30 min.Later,a quantitative grain boundary inter-connection char-acterization method based on EBSD and five parameter analysis was employed to statistically analyze the grain boundary character distributions within the samples.The results revealed that the cryo-rolled and recrystallized sample featured a higher proportion of the{111}/{111}NSB compared to the 25 ℃-rolled and recrystallized sample.Specifically,the{111}/{111}NSB fraction in the former reached 6.0%,2.22 times that in the latter.XRD analysis,hardness testing,and EBSD measurements revealed the de-velopment of a strong{011}<111ˉ>deformation texture in the samples rolled at 25 ℃ or the cryogenic tem-perature.In particular,cryo-rolling was found to impede dynamic recovery;hence,the sample rolled at this temperature featured higher levels of residual compression stress,increased grain fragmentation,and higher stored energy compared to the sample rolled at 25 ℃.Owing to the higher driving force and more active{011}<011ˉ>-oriented growth,the cryo-rolled sample formed larger grains and stronger{011}<011ˉ>recrystallization textures during the subsequent recrystallization annealing.Statistical analysis based on grain boundary tracing demonstrated that the grain boundaries between{011}<011ˉ>-oriented grains and other oriented grains contained higher proportions of the{111}/{111}NSB compared to the grain boundaries between two randomly oriented grains.Moreover,boundaries between the{011}<011ˉ>-oriented grains and their diffusive orientations featured notably high proportions of the{111}/{111}NSB.This explains the higher content of the{111}/{111}NSB observed in the cryo-rolled and recrystallized sam-ple than that in the 25 ℃-rolled and recrystallized sample.
作者
李振想
王卫国
Gregory S Rohrer
洪丽华
陈松
林燕
周邦新
LI Zhenxiang;WANG Weiguo;Gregory S Rohrer;HONG Lihua;CHEN Song;LIN Yan;ZHOU Bangxin(Institute of Grain Boundary Engineering,Fujian University of Technology,Fuzhou 350118,China;School of Materials Science and Technology,Fujian University of Technology,Fuzhou 350118,China;Department of Materials Science and Engineering,Carnegie Mellon University,Pittsburgh,PA15213-3890,USA;Institute of Materials,Shanghai University,Shanghai 200072,China)
出处
《金属学报》
北大核心
2025年第11期1673-1688,共16页
Acta Metallurgica Sinica
基金
国家自然科学基金项目No.51971063
福建省自然科学基金项目No.2021J011076。
关键词
高纯
AL
深冷轧制
近奇异晶界
晶界界面匹配
high purity aluminum
cryo-rolling
near singular boundary
grain boundary inter-connection
