Magnesium alloy defectology AZ91D high-pressure die cast and influence on the fatigue behaviour

Abstract

The fatigue results of a high-pressure die cast of AZ91D magnesium alloy revealed the presence of different types of casting defects, which account for the large scattering in the number of cycles until failure. In this paper, this magnesium alloy has been analysed, and in an effort to reproduce the same surface and material conditions exhibited in automotive service components, the fatigue test samples were manufactured using a die that employs the same casting process and equipment. To examine the fracture surface of all the fatigue tests, a scanning electron microscope was used, and the source of the failure, so as to relate fatigue life with casting defect type, was identified. Five casting defect types that influence the fatigue behaviour were observed and classified: (a) isolated pores (blowholes), (b) micro-porosity areas, (c) circular shrinkage cavities associated with the contraction and geometry of the casted specimen, (d) surface burrs associated with the die-casting mould and (e) the presence of oxides or inclusions. © 2013 Wiley Publishing Ltd.