HRTEM studies of aging precipitate phases in the Mg-10Gd-3Y-0.4Zr alloy  

作　　者：王冬舒 李德江 谢艳才 曾小勤 

机构地区：[1]National Engineering Research Center of Light Alloys Net Forming,School of Materials Science and Engineering,Shanghai Jiao Tong University [2]State Key Laboratory of Metal Matrix Composites,Shanghai Jiao Tong University

出　　处：《Journal of Rare Earths》2016年第4期441-446,共6页稀土学报（英文版）

基　　金：Project supported by the National Natural Science Foundation of China(51171113,51301107 and 51474149);China Postdoctoral Science Foundation(2012M511089,2013T60444)

摘　　要：Rare-earth（RE） element addition can remarkably improve the mechanical properties of magnesium alloys through precipitation hardening. The morphology, distribution and crystal structure of precipitates are regarded as major strengthening mechanisms in the Mg-RE alloys. In order to understand the formation of precipitates during aging at 225 oC in a Mg-10Gd-3Y-0.4Zr alloy（GW103K） with high strength and heat resistance, a high-resolution transmission electron microscopy（HRTEM） was employed to characterize the microstructural evolution. It was found that three types of precipitates were observed in the alloy at the early stage, named as： single layer D019 structure, one single layer D019 structure and one layer of Mg, two parallel single layers（containing RE） and Mg layer in between, which was regarded as ordered segregation of RE, precursors to form β′′ and β′ phase, respectively. Both of β′′ and β′ phase were transformed from the precursors. It was also found that large size of β′ phase and the small size of β′′ phase were constantly existent in the whole aging process. β′ phase played a major role in the strengthening of the GW103 K alloys and the decrease of the hardness was caused by the coarsening of β′ phase.Rare-earth（RE） element addition can remarkably improve the mechanical properties of magnesium alloys through precipitation hardening. The morphology, distribution and crystal structure of precipitates are regarded as major strengthening mechanisms in the Mg-RE alloys. In order to understand the formation of precipitates during aging at 225 oC in a Mg-10Gd-3Y-0.4Zr alloy（GW103K） with high strength and heat resistance, a high-resolution transmission electron microscopy（HRTEM） was employed to characterize the microstructural evolution. It was found that three types of precipitates were observed in the alloy at the early stage, named as： single layer D019 structure, one single layer D019 structure and one layer of Mg, two parallel single layers（containing RE） and Mg layer in between, which was regarded as ordered segregation of RE, precursors to form β′′ and β′ phase, respectively. Both of β′′ and β′ phase were transformed from the precursors. It was also found that large size of β′ phase and the small size of β′′ phase were constantly existent in the whole aging process. β′ phase played a major role in the strengthening of the GW103 K alloys and the decrease of the hardness was caused by the coarsening of β′ phase.

关 键 词：Mg alloys rare earth elements precipitates HRTEM 

分 类 号：TG146.22[一般工业技术—材料科学与工程] TG166.4[金属学及工艺—金属材料]