Al-Cu-Li合金厚板不均匀特征组织对蠕变时效成形的影响

Effect of inhomogeneous characteristic structure on creep aging forming in Al-Cu-Li alloy thick plates

采用单轴恒应力蠕变试验、电子背散射衍射(EBSD)和透射电子显微镜(TEM)技术等实验手段,研究了Al-Cu-Li合金厚板的不均匀组织特征对其蠕变时效成形过程的影响。结果表明:厚向不均匀组织的差异性表现出明显不同的蠕变变形行为,靠近中心层的特征组织具有更高的蠕变量和更快的初始蠕变速率;厚板特征组织的晶粒尺寸与蠕变变形之间无确定的相关性,而位错运动是影响蠕变量的主要因素;晶粒尺寸在蠕变时效前后变化微小,但蠕变时效后小角度晶界比例存在不同程度的提高。此外,厚板不同特征组织会影响蠕变时效过程中强化相T_(1)的析出行为,靠近中心层的特征组织在蠕变过程中会形成更多的位错缠结,促使T_(1)相大量析出和致密分布。

The effect of inhomogeneous structure on creep aging process of Al-Cu-Li alloy thick plate was studied by uniaxial constant stress creep test,electron backscatter diffraction(EBSD)and transmission electron microscope(TEM)techniques.The results show that the difference of the thick-direction inhomogeneous structures exhibits obvious different creep deformation behavior,and the characteristic structure near the center layer has a higher creep and a faster initial creep rate.There is no definite correlation between the grain size of the characteristic structure of the thick plate and the creep deformation,and the dislocation movement is the main factor affecting the creep.The grain size changes slightly before and after creep aging,but the proportion of smallangle grain boundaries increases to a varying degree after creep aging.In addition,the different characteristic microstructures of the thick plate could affect the precipitation behavior of the strengthening phase T_(1) during the creep aging process.The characteristic structure near the center layer forms more dislocation entanglements during the creep process,which promotes a large number of precipitation and dense distribution of T_(1) phase.