基于高精度三维X射线断层扫描技术, 对实际ADC12铝合金压铸件试样内部的微观孔洞进行了观察, 测量和计算了孔洞的体积、表面积、圆整度等特征参数, 分析了微观孔洞体积的总体特征. 根据孔洞的三维形貌和特征参数, 对气孔、气缩孔和缩孔3类微观孔洞的体积、圆整度和压力进行了分析与对比,探讨了各类孔洞的形成机制. 研究表明, 气孔、气缩孔和缩孔空间形貌复杂性增加, 而圆整度和压力下降,气缩孔具有最大的平均体积, 缩孔具有最小的平均体积. 使用统计方法对微观孔洞的体积进行了分析, 结果表明, 微观孔洞的体积符合三参数对数正态分布, 其拟合程度优于二参数对数正态分布.

Aluminum alloy castings have been widely applied in automotive and aerospace fields. One of themost common defects of cast aluminum alloys is pore, which often results in poor mechanical properties suchas limited strength and ductility, short fatigue life and increasing variability in properties. In this investigation,micropores in practical ADC12 aluminum high pressure die castings were detected with 3D high resolution X-raycomputed tomography technology. The 3D morphologies, volumes, surface areas and sphericity coefficients ofthe pores were presented and analyzed. The pore's general characterization was summarized. Based on theirdifferent morphologies and characteristics, there were three types of pores, namely, gas, gas-shrinkage andshrinkage pores, detected in the die casting alloys. The volumes, sphericity coefficients and pressures of the threetypes of pores were compared and discussed. Then their formation mechanism was proposed. It was concludedthat the gas pore was with low volume, high pressure and near round shape. The appearance of shrinkage-gaspore was sphere with convexes or long tails. Compared with the gas pore, the shrinkage-gas pore volume washigher while its pressure was lower by one order of magnitude. For the shrinkage pore formed during the highsolid fraction period, it was characterized with low volume and tortuous and complex shape in space. The sphericity and pressure of the shrinkage pore were the lowest among the three types of pores and its pressure wasapproximate three orders lower than that of the gas pore. Furthermore, the volume distribution of pores wasinvestigated by statistical analysis, which showed that the three-parameter lognormal can fit the volume distribution better than lognormal.