Effect of Pore-forming Agents Content on Porosity and Experimental Study on Porosity Measurement of Porous SiC Preform

The SiC preform was prepared by compression molding.The porosity of porous SiC preform was determined by Archimedes method,mass-volume method and mercury intrusion method,the measured results were compared.The results showed that the porosity measured by Archimedes method was small because the open porosity was large,the test results of mass-volume method and mercury intrusion method were near,then Al alloy volu-me fraction in AlSiC composite and porosities measured by the above three methods were also compared.The results proved that the porosity measured by mass-volume method has an excellent agreement with Al alloy volume fraction in AlSiC composite.Therefore the mass volume method is a simple and practical method of porosity measuring.Then the effects of the pore-forming agents content on the porosity of SiC porous preform were investigated.The results showed that the porosity rose unobviously with the content of pore-forming agents when content of pore-forming agents was less than5%;and that the porosity rose linearly in general when content of pore-forming agents was more than 5%.And the porosity tended to 40% when the pore-making agents content was 14%,which can fully meets subsequent Al infiltration requirements.