Abstract
Mechanical performance of cast aluminum alloys is strongly affected by the defects formed during solidification. For example, fractography studies of the fatigue specimens have shown that fatigue failure in aluminum castings containing defects is almost always initiated from defects, among which pores are most detrimental. However, elimination of these pores is neither always economically nor technically possible. This work characterizes defects in high pressure die cast aluminum alloy as an illustrative material, but the methods used can be applicable to other types of castings and defects. The defects were evaluated using metallography as well as micro-computed tomography techniques. The variability of defects between the specimens of two sizes as well as different porosity levels are studied statistically. The distributions of defects based on location within the specimens are also analyzed. Moreover, the maximum defect size within the specimens are estimated using extreme value statistics, which can be used as an input to fatigue life prediction models. Extreme value statistics is applied on both 2D and 3D defect data. The accuracy of each approach is verified by comparing the estimated maximum defect size within the specimens with the maximum observed defects on fracture surfaces of fatigue specimens.
Highlights
Cast aluminum alloys are increasingly used in producing a variety of components in different industries including aerospace, automotive, electrical, and railroad
Evaluating depends on where the random section is made. is increasing metallography examination examinationhighly highly depends on where the random section made
As the mechanical properties of cast components can be significantly affected by existing defects, evaluation of defects within specimens or components is of great importance in design
Summary
Cast aluminum alloys are increasingly used in producing a variety of components in different industries including aerospace, automotive, electrical, and railroad. The melt in HPDC is more turbulent during mold filling, which may result in substantial porosity due to entrapped air [2]. Porosities may result from shrinkage due to natural volume contraction of the melt [2,3] Oxide films represent another type of defects which is common in cast components. These oxide films may be formed during mold filling by surface turbulence or come from the crucible [4,5]. All these defects can result in significantly reducing mechanical properties such as strength and ductility in general, and fatigue performance in particular. Casting defects reduce the fatigue strength, and cause
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