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The first report on formation of Al-W-Cu grain boundary phase and its influence on mechanical behavior of 2D-WS<inf>2</inf> reinforced Al-4Cu alloy matrix composites

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Abstract
Nanostructured two-dimensional (2D) WS2 reinforced Al-4Cu alloy matrix composites were prepared via spark plasma sintering (SPS) at 550 and 570 °C. The microstructure and interface characteristics of the composites were investigated. In situ formation of Al-W-Cu ternary phase at the grain boundaries of the Al-rich matrix phase was observed on sintering. High-resolution transmission electron microscopy (HRTEM) and scanning TEM (STEM) with quantitative mapping confirmed that the structure of ternary Al-W-Cu (Al12W0.6Cu0.4) belongs to bcc phase (space group: Im3̅ (204), similar to that of binary bcc-Al12W phase. Such bcc intermetallic phase was absent in pure Al-matrix under identical sintering conditions. The ternary intermetallic phase along with the retained 2D-WS2 contributed to about 41% increase in the hardness of the alloy composite. Nanoindentation hardness and Young's modulus of the Al-W-Cu ternary intermetallic were found to be around 4.6 GPa and 104 GPa, respectively. The formation mechanism of Al-W-Cu intermetallic phase from 2D-WS2 nanosheets and Al-4Cu matrix was elucidated with Calphad (Calculation of Phase Diagrams)-based Gibbs energy analysis.
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A. Intermetallics, B. Mechanical properties, C. Powder metallurgy, D. Microstructure, E. Phase stability, F. Microscopy
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