Flow behavior and fracture of Al−Mg−Si alloy at cryogenic temperatures  

Al−Mg−Si合金在低温下的流变行为和断裂

作　　者：Danielle Cristina Camilo MAGALHAES Andrea Madeira KLIAUGA Vitor Luiz SORDI 

机构地区：[1]Department of Materials Engineering,Federal University of Sao Carlos−UFSCar,Rod.Washington Luiz,km 235,13565-905,Sao Carlos–SP,Brazil

出　　处：《Transactions of Nonferrous Metals Society of China》2021年第3期595-608,共14页中国有色金属学报（英文版）

基　　金：We would like to acknowledge the Sao Paulo Research Foundation(FAPESP)(Grant No.2014/15091-7 and 2016/10997-0);the Conselho Nacional de Desenvolvimento Científico e Tecnológico-Brazil(CNPq)(Grant No.449009/2014-9);This study was financed in part by the Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior-Brazil(CAPES)-Finance Code 001.Danielle Cristina Camilo MAGALHÃES acknowledges CNPq for her PhD scholarship(Grant No.153181/2013-3).

摘　　要：The tensile and fracture behaviors of AA6061 alloy were investigated in order to provide quantitative data about this alloy at cryogenic temperatures.Specimens of AA6061 alloy were solution heat treated before tensile tests at 298,173 and 77 K and tested at strain rates in the range from 0.1 to 0.0001 s^(−1).The results indicate the suppression of the Portevin−Le Chatelier(PLC)effect and dynamic strain aging(DSA)at 77 K.In contrast,at 298 K,a remarkable serrated flow,characteristic of the PLC effect,is observed.Furthermore,the tensile behavior at 77 K,compared with that observed at 173 and 298 K,shows a simultaneous increase in strength,uniform elongation,modulus of toughness,strain-hardening exponent and strain rate sensitivity,which is related to a decrease in the dynamic recovery rate at low temperature.These responses are reflected on the fracture morphology,since the dimple size decreases at 77 K,while the area covered by dimples increases.Comparisons of the Johnson−Cook model show that a good agreement can be obtained for tests at 173 and 77 K,in which DSA is suppressed.研究AA6061合金的拉伸和断裂行为,为该合金在低温范围内的拉伸和断裂行为提供定量数据。在298 K、173 K和77 K下对铝合金进行固溶处理,然后在应变速率为0.1~0.0001 s^(−1)条件下进行拉伸试验。结果表明,77 K时Portevin−Le Chatelier(PLC)效应和动态应变时效(DSA)被抑制。相反,298 K时,观察到PLC效应的特征,即明显的锯齿状流变。77 K固溶处理后样品的拉伸性能与173 K和298 K处理的样品拉伸性能相比,强度、伸长率、韧性模量、应变硬化指数和应变速率敏感性同时提高,这与低温下动态回复速率的降低有关。与之相对应,断口形貌结果显示,77 K处理的样品韧窝尺寸减小,而韧窝覆盖的面积增加。173 K和77 K处理的样品中DSA被抑制,其实验结果与Johnson−Cook模型模拟结果吻合较好。

关 键 词：cryogenic temperature aluminum alloy flow behavior strain rate sensitivity work-hardening behavior Johnson−Cook model FRACTURE 

分 类 号：TG146.21[一般工业技术—材料科学与工程]