Hasan F, Lorimer G W
Manchester Materials Science Centre, University of Manchester/UMIST, Great Britain.
Microsc Res Tech. 1993 Mar 1;24(4):359-66. doi: 10.1002/jemt.1070240409.
The distribution, morphology, chemistry, and crystallography of the precipitates formed during aging of an Al-Cu-Zn-Mg-Ag alloy have been studied using analytical transmission electron microscopy. The first precipitates to appear during aging at 150 degrees C were thin hexagonal-shaped plate-like precipitates which formed on the (111)Al planes. These precipitates had a face-centred orthorhombic crystal structure and their composition was essentially CuAl2 although they contained a trace of silver. At peak hardness the microstructure consisted of the plate-like precipitates on (111)Al planes and theta' precipitates on (100)Al planes. Overaging resulted in the precipitation of equilibrium theta, CuAl2, which exhibited a lath morphology and an orientation-relationship with the matrix (210)Al magnitude of (110)gamma; (001)Al misoriented from (001)gamma by approximately 6 degrees. Prolonged overaging at 250 degrees C resulted in the formation of cuboid-shaped Al5(Cu,Zn)6Mg2 precipitates which had a cubic crystal structure and a cube:cube orientation-relationship with the matrix.
利用分析型透射电子显微镜研究了Al-Cu-Zn-Mg-Ag合金时效过程中形成的析出相的分布、形态、化学组成和晶体结构。在150℃时效时首先出现的析出相是在（111）Al平面上形成的薄的六方板状析出相。这些析出相具有面心正交晶体结构，其成分基本上是CuAl2，尽管含有微量银。在硬度峰值时，微观结构由（111）Al平面上的板状析出相和（100）Al平面上的θ'析出相组成。过时效导致平衡态θ（CuAl2）析出，其呈现板条形态且与基体具有取向关系：（210）Al与（110）γ的夹角为（001）Al与（001）γ偏离约6°。在250℃长时间过时效导致形成立方体形的Al5（Cu，Zn）6Mg2析出相，其具有立方晶体结构且与基体具有立方-立方取向关系。
