Secondary-cast aluminum alloys have increasing industrial applications. Their biggest deficiency is their impurity content, especially Fe, which has low solubility in Al and almost all the content creates intermetallic phases. This work examines the effect of higher Fe content on the microstructure and properties of A356.0 alloy. At the same time, no other possibility existed to affecting the brittleness of the formation of the β phases. The calculation of Fecrit, ratio of Mn/Fe, quantitative and computed tomography analysis of porosity and Fe plate-like phases, measurement of mechanical and fatigue properties, and fractography analysis were performed in this study. The results show that gravity die casting into a sand mold, and the non-usage of Mn addition or heat treatment, do not have a negative effect on increasing the size of the Fe-rich plate-like phases. The longest Fe-rich phases have limited the pore growth and ratios, but their higher thickness led to greater porosity formation. The mechanical and fatigue properties correlate with the Fecrit level and the highest were for the experimental alloy with 0.454 wt.% of Fe. The experimental results confirmed the fact that if the Fe plate-like phases have a length of up to 50 µm, the fatigue properties depend more on the size of porosity. If the length of the Fe needles is more than 50 µm, then the properties are mainly affected by the length of these Fe phases.
Additive manufacturing has recently expanded its potential with the development of selective laser melting (SLM) of metallic powders. This study investigates the relation between the mechanical properties and the microstructure of Ti6Al4V alloy produced by SLM followed by a hot isostatic pressing (HIP) treatment. HIP treatment minimizes the detrimental influence of material defects. Tensile specimens produced with reference to specific building axes were prepared using a Renishaw A250 system. It has been found that the tensile strength and elongation depend on specimen building direction. Microstructural and textural characterizations were carried out to identify the source of differences.
In this study, the effect of the β-Al5FeSi phases on fracture surfaces in secondary AlSi7Mg0.3 cast alloys with common and higher amount of iron was investigated. Iron addition caused the formation of different Fe-rich intermetallic phases in aluminium alloys. Components made of secondary aluminium alloys commonly have a higher amount of such phases. Sharp needles as β-Al5FeSi phase lead to initiate stress tension, thereby contributing to increased risk of micro-cracks formation on the fracture surfaces. To determine the effect of β-Al5FeSi to fracture surfaces of AlSi7Mg0.3 cast alloy, SEM microscopy with energy-dispersive X-ray spectroscopy (EDX) was used to study the amount of needles phases, their morphology and violation wave. It was found that increasing Fe content increased the size and the number of Al5FeSi phases. The fractographic analysis of fracture surfaces shows an increasing amount of cleavage fracture in materials with a higher amount of iron, too.
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