2055铝锂合金热拉伸的显微组织与流变应力行为  

Microstructure and flow stress behavior of 2055 Al-Li alloy under hot tension

作　　者：刘宁[1] 肖代红[1] 刘文胜[1] LIU Ning;XIAO Daihong;LIU Wensheng(Science and Technology on High-strength Structural Materials Laboratory,Central South University,Changsha 410083,China)

机构地区：[1]中南大学轻质高强结构材料国防科技重点实验室,长沙410083

出　　处：《粉末冶金材料科学与工程》2020年第2期125-132,共8页Materials Science and Engineering of Powder Metallurgy

基　　金：预研基金资助项目(6142912180105,41422060204)。

摘　　要：用Gleeble-1500热模拟机对2055铝锂合金进行高温拉伸,研究合金在温度为480~540℃、应变速率为0.000 1~0.1 s^-1区间内的热变形行为,并通过光学显微镜(OM)、透射电镜(TEM)和扫描电镜(SEM)观察和分析合金的显微组织。结果表明:热拉伸过程分为3个阶段,各阶段的变形机制不同。热拉伸过程中表现出明显的流变稳态,合金的主要变形机制由动态回复向动态再结晶转变。在应变速率0.001 s^-1下,变形温度为480℃时,很难观察到再结晶晶核,变形温度为510℃和540℃时出现锯齿状晶界,且温度越高,锯齿状晶界越明显,该现象属于典型的几何动态再结晶;温度一定时,应变速率越低,合金的峰值应力越小,表明2055铝锂合金具有正应变速率敏感性。采用Sellars和Tegart提出的包含变形激活能Q和温度T的双曲线正弦函数本构方程来描述合金的热激活行为,热变形激活能为226.783 kJ/mol。The hot deformation behavior and microstructure evolution of 2055 Al-Li alloy have been investigated by subjecting the alloy to hot tensile tests carried out on Gleeble-1500 thermal simulator at the temperatures varied from 480?540℃and strain rates 0.0001?0.1 s^?1.The microstructures of the alloy during deformation was studied by OM,TEM and EBSD.The results show that there are three stages in the hot stretching process and the deformation mechanism is different in each stage.In the process of hot stretching,it shows obvious rheological stability,the change from dynamic recovery to dynamic recrystallization is the main mechanism.When strain rate is 0.001 s^?1 and deformation temperature is 480℃,the recrystallization nucleus are difficult observed.When the temperature are 510℃and 540℃,serrated grain boundary appears.The higher the temperature is,the more obvious phenomenon of serrated grain boundary appears,which belongs to typical geometric dynamic recrystallization.At a certain temperature,the lower the strain rate is,the smaller the peak stress of the alloy is,which indicates that 2055 Al-Li alloy has the sensitivity of normal strain rate.The constitutive equation of hyperbolic sine function including deformation activation energy Q and temperature T proposed by Sellars and Tegart are used to describe the thermal activation behavior of the alloy.The activation energy of thermal deformation is 226.783 kJ/mol.

关 键 词：铝锂合金 热变形 本构方程 流动稳态 动态回复 动态再结晶 

分 类 号：TG146.2[一般工业技术—材料科学与工程]