Fatigue Resistance of Self-hardening Aluminium Cast Alloy

Cast aluminium alloys are widely used in fatigue critical structural applications, such as engine blocks, cylinder heads, chassis and suspension components, to improve automotive fuel economy. However, it may be difficult to use these alloys for parts that require a high fatigue strength and high reliability because of a large number of casting defects as porosity and microshrinkages exist in them. Fatigue properties of cast aluminium components are controlled by maximum defect size in the material. The larger maximum defect size, the lower the fatigue strength and life.Self-hardening Al-alloys (Al-Zn-Si-Mg alloys) introduce an innovative class of light Al-alloys. Fatigue properties of AlZn10Si8Mg cast alloy in the high cycle region were tested by rotating bending fatigue loading in a high cycle region with the used of parameters - frequency f = 40 Hz, temperature T = 20 +/- 5 degrees C and stress ratio R = -1. Because of that large pores are near or at specimen's surface and its dominant reason of fatigue crack initiation and propagation. (C) 2017 Elsevier Ltd. All rights reserved

The Fatigue lifetime of AlZn10Si8Mg cast alloy with different percentage of iron

To increase the proportion of Al-cast alloys in a variety of industrial applications, it appears useful to control their fatigue behavior. In general, that behavior is affected by many factors, such as chemical composition, heat treatment, inclusions etc. The problem with utilization of the Al-scrap as a material for casting the Al-Si alloys lies in the fact that the scrap, unfortunately as a rule, is contaminated with iron. The Fe-rich intermetallics, formed during the solidification process, appear in a great variety of shapes and sizes. The most important are platelets or needles Al 5 FeSi, because they greatly decrease mechanical and corrosion properties of Al-cast alloys. The effect of the brittle Fe-rich phases on the fatigue properties in the secondary self-hardening AlZn10Si8Mg cast alloys with different percentage of iron (0.150 and 0.559 wt. %) was studied. Microstructure of alloys and the 3D-morphology of phases were analyzed by the optical and SEM microscopy. Rotating bending fatigue tests were realized for a defined number of cycles 3 x 10 6 . The results show that with increasing the content of Fe, the area proportion and the average length of Al 5 FeSi phases increased a significant influenced on the fatigue life and pores formation

The effect of iron content on fatigue lifetime of AlZn10Si8Mg cast alloy

The problem with utilization of the Al-scrap as a material for casting the Al-Si alloys lies in the fact that the scrap, unfortunately as a rule, is contaminated with iron. The current study presents an investigation of the effect of different iron contents (0.150 and 0.559 wt%) on microstructure, porosity and bending fatigue properties in the secondary (recycled) self-hardening AlZn10Si8Mg cast alloy. Rotating bending fatigue tests were realized for a defined number of cycles 3 x 10(6) with a stress asymmetry ratio R = -1 at room temperature. Observation by the optical and SEM microscopy using deep etching and image analysis highlight the role of the plate/needle-like Fe-rich intermetallic (Al5FeSi phase), formed during the solidification process. The quantitative metallography and CT scan was used to quantify the amount of pores.The results show that Al5FeSi phases play an important role in the low cycle region. The higher amounts of needle/plate like Fe-rich particles (Al5FeSi) with increased porosity degraded fatigue lifetime in the short and medium life-time regime ( < 10(6) cycles) and there was no effect or slight increases the fatigue lifetime for long life-time regime (>> 10(6) cycles). In the high cycle's region are the pores more detrimental than Fe-rich phases to the fatigue strength. Fracture surface of the fatigue specimens were analysed by SEM to characterize the micromechanism and the initiation fracture local