Study into the feasibility of obtaining dense materials based on AlN-SiC solid solution in one stage by SHS gasostatiс processing

Abstract

The synthesis and sintering of the (AlN)x(SiC)1–x solid solution were studied under the conditions of SHS gasostatiс processing at high nitrogen gas pressures (up to 110 MPa). Phase formation during the combustion of aluminum and silicon carbide mixtures with the different amount of a combustible component (aluminum content is 35 to 60 wt.%) was studied. It was shown that the optimal amount of aluminum mixed with silicon carbide to obtain a single-phase solid solution (with the complete Al conversion to AlN and without SiC dissociation) is 45–50 wt.%. A mixture with 55–60 wt.% Al leads to excessively high temperatures, which in turn leads to the silicon carbide decomposition to Si + C elements. The optimal parameters for obtaining a dense material in one stage were determined. The measured porosity and density of materials obtained demonstrated that preforming is essential for the final density of samples containing 50 wt.% Al: maximum density was achieved at a preforming pressure of 10 MPa. It was found that the 5 wt.% yttrium oxide additive increases the material density by almost 10 %. A similar effect is also obtained by increasing the initial gas pressure from 80 to 110 MPa. The maximum density in this case reached 2.7 g/cm3, i.e. 83 % of the theoretical density. The total volumetric shrinkage of the material was 10 ± 0.5 %, and this indicator can be almost completely smoothed over by the 3 wt.% boron additive. The microhardness of samples was 2000 kg/mm2.