Papers by Author: Teruyoshi Munekata

Abstract: Rod-shaped precipitates in Al -1.1 mass% Mg2Ge (balanced) and Al -1.0 mass% Mg2Ge – 0.5 mass% Mg (excess Mg) alloys 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 <100> directions of the matrix. There were 2 groups for rod-shaped precipitates in the base alloy, namely, small cross sections about 10 nm and large ones over 20nm 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.

Abstract: In this work, the crystal structure of the rod-shaped precipitate in aged Al -1.0 mass% Mg2Ge alloy at 523 K has been investigated by high resolution transmission electron microscopy (HRTEM), electron diffraction technique and energy dispersive X-ray spectroscopy (EDS). The rod-shaped precipitate in its alloy has showed the similar arrangement of bright dots in its HRTEM images and selected area diffraction pattern (SADP) to those of the b’-phase in Al-Mg2Si alloy. But a lattice constant of this precipitate in Al-Mg2Ge alloy was slightly larger than the b’-phase in Al-Mg2Si alloy. In addition, the new metastable phase has been found out in Al-Mg-Ge alloy.