3-D Microstructural Distribution and Mechanical Analysis of HPDC Hypereutectic Al-Si Alloys via X-Ray Tomography

Abstract

The microstructure of different hypereutectic Al-Si alloy prepared by high pressure die casting (HPDC), including pores, primary silicon particles (PSPs) and Cu-rich phases was characterized using synchrotron X-ray tomography. With the microstructure distribution, the tensile crack surfaces were analyzed based on the laboratory CT reconstruction techniques, without which previous mechanical failure analysis was hard to conduct due to the low elongation of such alloy. The fractography feature agreed well with the microstructure feature and revealed the crack extension route during fast fracture. Besides, such technique provided a new method for analyses of other mechanical failure such as fatigue and reconstructed fractography and SEM observation offered new quantitative analyses of crack propagation. Generally, the existence of PSPs in the hypereutectic Al-Si alloy had an effect on the mechanical performance by influencing the crack propagation route no matter in tensile crack and fatigue failure.