摘要
采用TEM和HAADF-STEM技术,研究Mg-7Gd-3Y-1Nd-1Zn-0.5Zr合金在240℃等温时效过程中析出相的形态与晶体学特征。经2h欠时效,析出相为稀土原子柱呈六角环状结构的有序溶质团簇、之字形GP区和早期形成的β'相。经18h峰时效,析出相主要为β'相和与其伴生的一种新型棒状相β'p。经100h过时效,析出相为β'相、β1相、长程堆垛有序(LPSO)构建块γ′相和14H-LPSO。β'相三维形貌呈凸透镜状,沿<0001>α方向观察,其长宽比小于EW75合金中β'相的长宽比。该合金优异的热稳定性归功于γ′和14H-LPSO阻碍β'和β1的生长、稀土原子低的扩散速率以及β'和β1相的物理特性。
The morphology and crystal structure of the precipitates in Mg-7Gd-3Y-1Nd-1Zn-0.5Zr alloy during isothermal ageing at 240 ℃ were investigated using transmission electron microscopy (TEM) and high-angle annular dark- eld scanning transmission electron microscopy (HAADF-STEM). After under-ageing for 2 h, the precipitates in the alloy are ordered solute clusters with rare earth atomic columns exhibiting hexagonal ring structure, zigzag GP zones and β' in its early formation. After peak-ageing for 18 h, the precipitates are mainly β' and new rod-like β'p accompanied with β'. After over-ageing for 100 h, the precipitates are β',β1, long-period stacking ordered (LPSO) building block known as γ′ and 14H-LPSO.β' has the three-dimensional shape of convex lens with smaller length-to-width ratio viewed along <0001>α than that in the EW75 alloy. The excellent thermal stability of this alloy can be attributed to the γ' and 14H-LPSO retarding the growth of β' and β1, low diffusion rate of rare earth atoms and physical character of β' and β1.
作者
刘伟
杜志伟
李婷
张奎
韩小磊
彭永刚
张婧
袁家伟
刘淑凤
庞铮
Wei LIU;Zhi-wei DU;Ting LI;Kui ZHANG;Xiao-lei HAN;Yong-gang PENG;Jing ZHANG;Jia-wei YUAN;Shu-feng LIU;Zheng PANG(Guobiao (Beijing) Testing & Certification Co.,Ltd.,Beijing 100088,China;National Center of Analysis and Testing for Nonferrous Metals and Electronic Materials,GRINM Group Co.,Ltd.,Beijing 100088,China;China United Test & Certification Co.,Ltd.,Beijing 100088,China;State Key Laboratory of Non-ferrous Metals & Processes,GRIMAT Engineering Institute Co.,Ltd.,Beijing 101407,China)
基金
Projects(51871195,51501015) supported by the National Natural Science Foundation of China
Project(TC170A5SU-1) supported by Ministry of Industry and Information Technology,China
关键词
镁合金
时效
析出相
长程堆垛有序相
magnesium alloy
ageing
precipitate
long-period stacking ordered (LPSO) phase