Solid-state synthesis of Cr2AlC MAX phase from mechanically activated Cr/ Al/C powder blends

Abstract

This study focuses on synthesizing the ternary-layered chromium aluminum carbide phase (Cr2AlC MAX) via a milling-assisted solid-state synthesis method. The elemental powders of Cr, Al, and C were processed in a twostage process following mechanical activation (MAc) and annealing. Various parameters in both stages (such as milling time, annealing temperature, and process control agent) were examined to optimize the production of a high-purity Cr2AlC MAX phase. For this purpose, the elemental powders underwent MAc through high-energy ball milling for 1, 3, and 5 h and annealing at temperatures ranging from 700 to 1500 degrees C. The formation mechanism of the Cr2AlC phase was discussed based on detailed characterizations, including differential thermal calorimetry (DSC), X-ray diffraction (XRD), and Rietveld analyses. Additionally, the morphological properties of the synthesized powders were investigated in detail via scanning and transmission electron microscopy (SEM and TEM) techniques. The initial formation of the MAX phase was observed at 700 degrees C, and it was completed with a meager amount of chromium carbide phase at higher temperatures (99.7 % Cr2AlC at 1100 degrees C) depending on the synthesis conditions. In addition, a single-phase Cr2AlC MAX without a carbide impurity was achieved with the addition of SA, which caused an increase in the annealing temperature to 1300 degrees C.