透過型電子顕微鏡

常眞 川畑, 健二 松田, 重晴 鎌土, 陽 小島, 進 池野

健二 松田, 照善 宗像, 常眞 川畑, 保裕 上谷, 進 池野

Rod-shaped precipitates in Al–1.1mass%Mg2Ge (Al–0.52at%Mg–0.24at%Ge) alloy aged at 523 K were observed by high-resolution transmission electron microscope (HRTEM) to understand their crystal lattices and chemical compositions. Rod-shaped precipitates were parallel to l100r directions of the matrix. There were 2 groups for rod-shaped precipitates, namely, small cross sections about 10 nm and large ones over 20 nm in diameter. Small precipitates showed a hexagonal network of bright dots in their HRTEM images, and its crystal lattice was estimated as a hexagonal having a=0.72 and c=0.405 nm based on analysis of HRTEM images and selected area electron diffraction (SAED) patterns. This lattice parameter was slight larger than that of the β′-phase in Al–Mg–Si alloy. Its orientation relationship with the matrix was as follows: {0001}p//{001}m, l1120rp//l100rm. Precipitates having large cross section showed a rectangular network having 0.68 and 0.35 nm. This was similar feature to the A-type precipitate in the Al–Mg–Si alloy with excess Si. A crystal lattice of this precipitate was estimated as a hexagonal having a=0.405 and c=0.68 nm based on analysis of HRTEM images and SAED patterns. Mg and Ge elements were detected from these precipitates by energy dispersive X-ray spectroscopy (EDS) and the ratio of Mg to Ge (Mg/Ge) for the small precipitate which is similar to the β′-phase in Al–Mg–Si alloy, was about 3, not 2. The Mg/Ge for large precipitates which are similar to the A-type precipitate in Al–Mg–Si alloy was 2, and this ratio was larger than that of the A-type precipitate in Al–Mg–Si alloy. It has been expected that these differences of chemical composition for precipitates caused the increment of lattice parameters of precipitates in Al–Mg–Ge alloy.

N. Wan, S. Lei, Jun Xu, M. Matteo

剛久 山本, 亜侑 小平

Yuki Kimura, Hiroyasu Katsuno, Shizuka Hirakawa, T. Yamazaki