Synthesis And Properties Of Cr₂AlC And Its Solid Solution

Chromium aluminum carbide(Cr₂AlC) has attracted most attention because it combines the merits of both metal and ceramic.It is easily machinable,resistant to thermal shock and oxidation,and it has excellent electrical conductivity and high strength at high temperature.However,the present methods and starting compositions can't guarantee the formation of a single phase Cr₂AlC owning to the appearance of impurity,which deteriorates some properties of Cr₂AlC.In the present work,the starting composition and sintering parameters were systematically studied to obtain a single phase Cr₂AlC.On the basis of research,we draw the following conclusions:A single phase Cr₂AlC has been synthesized by pressureless sintering Cr,Al and C powders with mole ratios of 2:(1,1.2and 1.3):1 in the temperature range of 1350～1450℃for 10min in Ar atmosphere.From the point view of industrial,a broad synthesized temperature range with a short time is beneficial for mass-producing Cr₂AlC.Cr₂AlC bulk ceramics were also obtained by hot pressuring Cr,Al and C powders with mole ratios of 2:(1.2 and 1.3):1 at 1450℃under 30MPa for 1h in Ar atmosphere.It is not easy to obtain a Ti-containing Cr₂AlC solid solution,the existence of Ti in the starting powders results in the formation of a Ti₂AlC-Ti₃AlC₂-Cr₂AlC composite. However,a Si-containing Cr₂AlC solid solution can be formed.The amounts of Si dissolve into Cr₂AlC are 0.1～0.2mole.If the amount of Si exceeds 0.2mole,a Cr₅Si₃/Cr₂AlC composite forms.SEM and XRD were used to characterize the synthesized materials,and their mechanical properties were measured.