β-Mg_5Gd平衡相原子尺度的HAADF-STEM表征
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摘要
本论文使用球差校正的高角环形暗场扫描透射电镜(Aberration-Corrected High-Angle Annular Dark-Field Scanning Transmission Electron Microscopy,HAADF-STEM)结合选区电子衍射(Selected Area Electron Diffraction,SAED)技术系统表征了Mg-19.6 wt.%Gd合金300℃等温时效100 h后的时效析出行为。研究结果表明,Mg-19.6 Gd合金时效后期析出的平衡相为β-Mg_5Gd。β-Mg_5Gd相为fcc结构(空间群:■;晶格参数:a=22.34?),呈透镜状。β-Mg_5Gd相具有一个■的惯习面,它们沿■3个方向均匀分布。β-Mg_5Gd相在β1-Mg3Gd中形核,并由内而外生长取代β1相。β相与β1,以及与α-Mg基体都是完全共格的,其与β1相、基体的取向关系为[110]β//[110]β1//[0001]α;■。
The precipitation behavior of the Mg-19.6 wt.% Gd binary alloy isothermally aged at 300℃ for 48 h was been characterized by means of aberration-corrected high angle annular dark field-scanning transmission electron microscopy(HAADF-STEM) combined with selected area electron diffraction(SAED) techniques.It is determined that the equilibrium β phase of Mg-Gd binary alloy is the Mg_5Gd intermetallic compounds,which has a face-centered cubic structure(fcc,space group ■;a=22.34?).The lenticular-shaped β-Mg_5Gd phases with a ■ habit planes,and precipitated and distributed uniformly in three directions of ■.The β-Mg_5Gd phase nucleation and growth in the existing β1-Mg3Gd,and gradually replaced the β1 phase from inside-out.In addition,the results indicate that the β/α-Mg and β/β1 interfaces are fully coherent,and the orientation relationship among β,β1 and α-Mg matrix is■ and [110]β//[110]β1//[0001]α.
The precipitation behavior of the Mg-19.6 wt.% Gd binary alloy isothermally aged at 300℃ for 48 h was been characterized by means of aberration-corrected high angle annular dark field-scanning transmission electron microscopy(HAADF-STEM) combined with selected area electron diffraction(SAED) techniques.It is determined that the equilibrium β phase of Mg-Gd binary alloy is the Mg_5Gd intermetallic compounds,which has a face-centered cubic structure(fcc,space group ■;a=22.34?).The lenticular-shaped β-Mg_5Gd phases with a ■ habit planes,and precipitated and distributed uniformly in three directions of ■.The β-Mg_5Gd phase nucleation and growth in the existing β1-Mg3Gd,and gradually replaced the β1 phase from inside-out.In addition,the results indicate that the β/α-Mg and β/β1 interfaces are fully coherent,and the orientation relationship among β,β1 and α-Mg matrix is■ and [110]β//[110]β1//[0001]α.
引文
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[6]Nie J F. Preface to viewpoint set on:phase transformations and deformation in magnesium alloys[J]. Scripta Materialia,2003,48:981-984.
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[22]Liu N Y,Zhang Z Y,Peng L M,et al. Microstructure evolution and mechanical properties of Mg-Gd-Sm-Zr alloys[J]. Materials Science and Engineering A,2015,627:223-229.