Study of gas and shrinkage porosity in Al-Si die cast couplings using X-ray micro-computed tomography

Abstract

The purpose of this work is to demonstrate the feasibility of a quantitative methodology to study 3D porosity in two Al-Si die cast couplings from an air-suspension system of heavy-duty vehicles, using X-ray micro-computed tomography and digital image processing. Although both parts are homologous, one was rejected for commercialisation due to a leak detected during a pneumatic test. The image post-processing, carried out using VGSTUDIO MAX 3.0 software, enabled the design of a strategy to evaluate and compare pore subpopulations in regions of interest (ROIs) of both parts. Based on the compactness parameter, it was possible to segment pore subpopulations according to their origin: gas and shrinkage. The results shows that the gas porosity volumes in the ROIs of both parts are similar. However, the shrinkage porosity volume is higher in the ROI of the rejected part, which involves changes introduced in the mould filling pressure and/or speed that affected solidification in this part. Finally, the quantitative methodology proposed in this work could be a valuable tool in the stages of research, product development, and quality control of both cast parts and other porous components obtained from different manufacturing processes.