The effect of milling time and heat treatment on the synthesis of the Cr₂AlC MAX phase

Synthesis of the Cr2AlC MAX phase was investigated by mechanical alloying. Cr, Al, and C powders were milled and heat treated at temperature range of 500-1300 degrees C for 1 h. X-ray diffraction and differential thermal analysis were used to study the reaction mechanisms and a scanning electron microscope was used to observe the microstructures. The Cr7C3 and Cr-Al compounds were formed by reactions among the initial elements. These compounds transformed to the Cr2AlC phase by increasing the temperature. The maximum amount of Cr2AlC phase was equal to 97.23 wt.%, which was related to the sample with 45 h of ball milling and subsequent heat treatment at temperature of 700 degrees C. DTA results showed a major exothermic peak at about 685 degrees C, which represents the formation of the Cr2AlC. This indicates that most conversions are completed in a single stage, below the temperature of 800 degrees C.