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利用透射电镜技术研究了快速凝固粉末A1-3.42Li-0.82Mg-0.12Zr合金的时效析出,并观察了时效过程中δ’相的析出与拉伸性能的关系。δ’为合金的时效强化相。533℃淬火后在自然时效状态下电子衍射揭示已有δ’相析出。110℃时效后δ’相明显可见,190℃时效后颗粒长大且分布较广,此时强度较高。230℃时效后δ’已回溶,合金软化。也观察了190℃下不同时间保持对组织与性能的影响。实验表明,合金中存在两种Al_3Zr相。微小颗粒的亚稳定的面心立方点阵的有序Al_3Zr相均布于晶内,而粗大颗粒的稳定的四方点阵的Al_3Zr相沿原粉末颗粒边界和晶界析出。前者成为时效时δ’相析出的生核处,形成δ’/Al_3Zr复合析出物。
The precipitation of the rapidly solidified A1-3.42Li-0.82Mg-0.12Zr alloy was investigated by transmission electron microscopy and the relationship between the precipitation and tensile properties of δ ’phase during aging was observed. δ ’is the aging strengthening phase of the alloy. The electron diffraction at 533 ℃ after natural aging reveals that the δ ’phase has been precipitated. After the aging at 110 ℃, the δ ’phase is obviously visible. After 190 ℃ aging, the particles grow and distribute widely, and the strength is higher at this time. After aging at 230 ℃ δ ’has been dissolved, the alloy softened. The effect of maintaining the microstructure and properties at 190 ° C for different times was also observed. Experiments show that there are two Al_3Zr phases in the alloy. The ordered Al_3Zr phase of the metastable face-centered cubic lattice of fine particles is uniformly distributed in the crystal, while the Al_3Zr phase of the stable tetragonal lattice of the coarse particles is precipitated along the boundaries of the original powder particles and the grain boundaries. The former becomes a nucleation site where the δ ’phase is precipitated during aging, and a δ’ / Al_3Zr composite precipitate is formed.