The isothermal section of the Fe-Zn-Nb ternary system at 600 oC was determined using the equilibrated alloys with the aid of diffusion couple approach. The specimens were investigated by means of SEM-EDS analysis, SEM-WDS analysis and X-ray diffraction. A true ternary phase T was identified, this phase is in equilibrium with ε, NbZn3, Γ, δ, and η - Zn phases respectively in the system. The solubility of Nb in η - Zn and δ phase is limited and that of Zn in ε is up to 10.0%.
The impact of Mg on the solidification structure of hypereutectic Al–Si alloys with different Si contents (15 wt% and 18 wt%) was investigated. 3%Mg was added to Al–15Si alloy to modify the phases in the solidification structure for the improvement of mechanical properties, and T6 heat treatment was used to optimize the microstructure and precipitate strengthening phase. The solidification structure was observed by OM and TEM respectively, and the precipitation behavior of each phase was detected through DSC. The results show that the addition of Mg decreased the undercooling of the alloy melt, thus suppressing the precipitation of primary Si phase. Nanoscale β" precipitates were precipitated in the matrix after T6 heat treatment. This resulted in an increase of 54% and 165% in the UTS and EL of the alloy, reaching 252 MP and 15.1%, respectively. Primary Si crystals were present in two forms in Al–18Si–8Mg alloy: spinel twin and non-twin, while Mg2Si always maintained the faceted crystals during the growing process, where only (100) and (111) crystal planes were observed. XRD, SEM and EBSD have been used to prove that Mg2Si crystals with different morphologies could become the heterogeneous nuclei of two types of primary Si crystals. The process of nucleation and growth of primary Si with Mg2Si as the heterogeneous nuclei was experimentally analyzed and theoretically predicted.
Hot dip galvanized zinc‐aluminum‐magnesium steel plates are widely used in fields such as power communication, automotive manufacturing, and marine engineering due to their excellent corrosion resistance. The use of microalloying can further improve their corrosion resistance. The effects of B on the microstructure and corrosion resistance of Zn–6Al–3Mg (ZAM) alloy coatings are systematically examined. Data indicates that the eutectic structure of the coating progressively refines as B content increases, concomitant with a reduction in the thickness of the Fe 2 Al 5 inhibition layer owing to the augmented formation of an Al‐rich phase at the surface. When the addition of B reaches 0.12%, the microstructure of the alloy coating is minimized, and there is no further reduction in the thickness of the Fe 2 Al 5 inhibition layer. Moreover, the presence of B diminishes the corrosion current density and bolsters corrosion resistance. Optimal corrosion performance, indicated by maximal density and uniformity of surface corrosion products and the lowest corrosion current density, is achieved at a B addition of 0.12%. The judicious selection of B content is pivotal for enhancing the microstructural and anti‐corrosive properties of ZAM alloy coatings. Therefore, adding 0.12% B to ZAM alloy can effectively improve the microstructure and corrosion resistance of the alloy coating.
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