The first report on formation of Al-W-Cu grain boundary phase and its influence on mechanical behavior of 2D-WS2 reinforced Al-4Cu alloy matrix composites

Nanostructured two-dimensional (2D) WS2 reinforced Al-4Cu alloy matrix composites were prepared via spark plasma sintering (SPS) at 550 and 570 degrees 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: Im (3) over bar (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. (C) 2021 Elsevier B.V. All rights reserved.