The metallograph of AlSi/BN seal coating was analyzed using Image-Pro Plus 6.0 combined with Adobe Photoshop CS6 to calculate its porosity. The effect of determination method of threshold and metallographic magnification on the calculated porosity was discussed. The porosity calculated by the method was compared with that determined by Archimedes method. The way, in which the metallograph is treated by gray processing first, then its contrast is adjusted so as to distinguish porous parts from other parts, thereby ascertain the threshold and a 50× magnification are reasonable. The porosity obtained by image analysis method is a little larger than the one obtained by Archimedes method, but closer to the reference value offered by the seal coating producer, which was determined by quantitative metallography. This method is simple and reliable. The accuracy of results can be guaranteed through determining the threshold at several locations and then averaging.%使用Image-Pro Plus 6.0结合Adobe Photoshop CS6软件分析AlSi/BN封严涂层的金相照片并计算其孔隙率.讨论了阈值选取方法和金相放大倍率对计算所得孔隙率的影响,并与用阿基米德法测得的孔隙率进行比较.对金相照片进行灰度处理,再调整对比度以便区分孔隙与非孔隙部分,从而确定阈值的方法以及采用50放大倍率比较合理.用图像分析法所得孔隙率略大于用阿基米德法所得孔隙率,但更接近封严涂层厂家提供的以定量金相法测得的孔隙率参考值.该方法简便、可靠,通过多区域确定阀值取其平均值可以有效保证结果的准确性.
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