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This study aims to clarify the growth process of the β-phase in Al-Mg-Si alloys from the point of view of morphological evolution. The orientation relationship, shape, growth process, misfit value, and interfacial condition between the β-phase and Al matrix were investigated using high-resolution transmission electron microscopy (HR-TEM), focused ion beam (FIB), and optical microscope (OM). In a previous study, the growth process and shape of the β-phase were determined using scanning electron microscopy (SEM). It was proposed that the truncated octahedron (8{111}, 6{100} facets) transforms into a hexahedron (6{100} facets). This study proposes that two new three-dimensional shapes of the β-phase exist between the truncated octahedron and hexahedron, and we identified the {111} β facets at the edges of the β-phase. We proposed the morphology evolution during the growth process of Mg 2 Si crystals and calculated the misfit to understand that the unstable {111} β facet has a higher misfit value compared to the {001} β and {011} β facets. Our observations provide insight into how they influence the behavior of Mg 2 Si crystals, which is crucial for predicting the microstructural evolution of Al-Mg-Si alloys and for designing materials with desired properties. • Investigated the morphology evolution of the β-phase in Al-Mg-Si alloys. • Explored β-phase orientation relationship, shape, and growth process using HR-TEM, FIB, and OM. • Discovered {111} β facets and proposed new three-dimensional shapes for the β-phase. • Calculated misfit values, revealing the instability of the (111) β facet compared to (001) β and (011) β facets. • Contributed to understanding microstructural evolution in Al-Mg-Si alloys and material design. [ABSTRACT FROM AUTHOR]

Pre-stretched strains, 2%, 4%, and 6%, were conducted on the friction-stir-welded dissimilar 2024-to-7075 aluminum alloy joints for strengthening purpose. Tensile tests and microhardness measurements were performed to evaluate the strengthening effect. Transmission electron microscopy and high resolution transmission electron microscopy examinations were employed to characterize precipitates and dislocation structures of the as-welded and pre-stretched joints to elucidate the intrinsic strengthening mechanisms. Results showed that the yield and tensile strengths of the pre-stretched 6% joint respectively increased 147.9 MPa and 31.1 MPa when compared with the as-welded joint. The strain hardening rates of 2024 lower hardness zone (LHZ)-II and 7075 LHZ were higher at the pre-stretched strain rate of 1 mm/min than those of 2 mm/min based on the microhardness area evolution. The yield sequence of the as-welded joint was 2024 LHZ-II, 2024 LHZ-I, 7075 LHZ, stir zone (SZ), and 2024 base material. The appearance of dislocation tangles, dislocation walls, dislocation cells, dislocation pile-ups in the 2024 LHZ-II and 7075 SZ combined with the severe interactions between dislocation structures and precipitates were the dominant strengthening factors. It was very interesting that dislocations provided a diffusion path for Mg atoms and Cu atoms in 2024 LHZ-II during the pre-stretching process. • Pre-stretching was used to strengthen the FSWed dissimilar aluminum alloys joints. • Yield sequence of the FSWed dissimilar aluminum alloys joints was identified. • The strengthened lower hardness zone contributed to the reinforced global joint. • Several kinds of dislocations structures induced by the pre-stretching process. • Dislocations provided a diffusion path for Mg and Cu atoms in 2024 aluminum alloy. [ABSTRACT FROM AUTHOR]

Boron doped diamonds (BDD) with boron concentration above 1019 at./cm3, grown under conditions of high isostatic pressure by the temperature gradient method, were studied by Transmission Electron Microscopy methods, EELS analysis and X-ray diffraction analysis. It was shown that boron is distributed unevenly in the grown crystal. It was found that in places of maximum boron content, interplanar distances d 111 increase from 0.206 to approximately 0.2065 nm. Parallel bands were discovered, the boundaries of which are fragments of the intermediate carbon phase (ICP-phase). Numerous twins along the {111} plane, as well as fragments of rhombohedral 9R phase, were discovered. [Display omitted] [ABSTRACT FROM AUTHOR]