Effect of composition and processing on phase assembly and mechanical property of Cr2AlC ceramics

The effect of composition and processing parameters, such as sintering temperature, dwell time and atmosphere as well as particle size of the starting material on the phase assembly and mechanical properties of Cr2AlC ceramics was studied. The results indicated that with additional Al from 10 to 60 at% in the composition, the amount of Cr2AlC phase in the samples that were hot-pressed under Ar increased together with decrease in the amount of the second phase, Cr7C3. Cr2AlC became the only phase in the sample when additional Al was more than 10 at%. On the other hand, the bulk densities of the samples decreased gradually with increase in Al in the composition. For fixed composition Cr:Al:C = 2:1.1:1, hot-pressing at 1350 °C for 1 h yielded Cr2AlC as a major phase together with a very small amount of Cr7C3. Further increase in temperature or extension of dwell time did not change the phase assemblage obviously. Preparation of Cr2AlC ceramics under N2 instead of Ar resulted in the formation of AlN in the sample besides Cr2AlC and Cr7C3. The hardness of the sample was increased from 3.5 GPa using coarse powder as starting material to 4.5 GPa by using fine powder with the same processing conditions.