Synthesis And Properties Of (Cr_1-xMn_x)₂AlC Solid Solution Materials

Cr2AlC combines the advantages of both ceramics and metals, having good electrical and thermal conductivities, resistance to thermal shock, oxidation and corrosion, etc. Recently, Mn-containing (Cr,Mn)2AlC solid solutions have attracted much attention due to their magnetic properties. The magnetic property of (Cr,Mn)2AlC gradually increases with Mn content. However, so far the maximum solubility of Mn in a (Cr,Mn)2AlC bulk material has been only 3 at.%. To further improve the content of Mn incorporation into (Cr,Mn)2AlC bulk materials, a new AlCr2/C/yMn (y=0.1,0.2,0.3, 0.5mole) mixture was adopted to prepare (Cr,Mn)2AlC solid solutions; the mechanical and thermal properties of (Cr,Mn)2AlC solid solutions were measured.(Cr,Mn)2AlC solid solutions were synthesized by pressureless sintering a mixture of AlCr2/C/yMn with a molar ratio of 1:1:y(y=0.1,0.2,0.3 and 0.5) at 1400℃ for 1 h in Ar. As y equals 0.1,the solubility of Mn is 2.7 at.%, corresponding to a resultant solid solution (Cr0.95Mn0.05)2AlC; as y equals 0.5, the maximum solubility of Mn is 8.3 at.%, corresponding to a resultant solid solution (Cr0.83Mn0.17)2AlC. XRD analysis showed that unwanted impurities such as Cr7C3 in the sintered samples appeared with increasing the Mn content in the starting mixture.A nearly pure (Cr0.95Mn0.05)2AlC ceramic has been prepared by pressureless sintering the mixture of AlCr2/C/0.1Mn at 1400℃ for 1 h in Ar atmosphere. A dense (Cr0.95Mn0.05)2AlC ceramic has been achieved by hot pressing the mixture of AlCr2/C/0.1Mn at 1350℃ with 25 MPa for 1 h.The mechanical properties of (Cr0.95Mn0.05)2AlC were measured. The flexural strength of the produced (Cr0.95Mn0.05)2AlC ceramic was about 350 MPa, lower than 398 MPa for Cr2AlC. The Vickers hardness for (Cr0.95Mn0.05)2AlC was about 3.3 GPa, marginally higher than 3.2 GPa for Cr2AlC in the load range of 1-20 kg. The above values suggest that the solid solution effect is slight.