Mg-12Gd合金的时效析出行为

摘要

The precipitation behavior of Mg-12Gd alloys during single aging process was studied by the synchrotron radiation small angel X-ray scattering (SAXS), transmission electron microscopy (TEM) analysis and Vickers hardness test. The results show that main precipitates of Mg-Gd alloy during aging process areβ′phases, and with the increase of aging time, the radial size of precipitates increases notably, whereas, the width of the precipitates increases a little. Therefore, the shape of the precipitates gradually changes into oval shape. The gyration radius of the precipitation particles is 12.9 nm after aging at 175 ℃ for 180 h, and with the increase of aging time to 360 h, the gyration radius of precipitation particles increases to 13.4 nm. And the size of the precipitation particles increases with the increase of aging time and goes to a stable value at last. The TEM results show that main precipitates after aging at 175 ℃ for 296 h areβ′phases with width of 5 nm and length of 13 nm, and a fewβ″phases exist, which is consistent with the results of small angel X-ray scattering. Scattering curves of alloys aged at 200 ℃ for 30 min show that precipitates exist and the gyration radius of precipitation is 2.5 nm, while gyration radius of the precipitates after aging at 225 ℃ for 30 min is 2.9 nm.%通过同步辐射小角度X散射实验方法(SAXS)、透射电镜(TEM)分析和维氏硬度测试，研究Mg-12Gd合金等温时效过程中的析出强化行为。结果表明：Mg-Gd合金时效过程中主要析出相为β′相，随着时效时间的增加，析出相的径向尺寸明显增大，宽度方向增加较小，逐渐演变成为椭圆形。175℃时效180 h时，析出相回转半径为12.9 nm；随着时效时间延长到360 h，析出相长大为13.4 nm；随着时效时间继续延长，析出相的尺寸增长速率减慢并最终趋向稳定。透射电镜结果表明：在175℃时效296 h时析出相大部分为β′相，有少量的β″相，β′相是宽5 nm，长13 nm的椭圆形，与小角度X散射结果一致。通过在200℃时效30 min的散射曲线能看出有析出相析出，刚析出时回转半径为2.5 nm，在225℃时效30 min时，析出相的回转半径为2.9 nm。