Relation between Mechanical Properties and Microstructure of Cast Aluminum Alloy AlSi9Cu3

One common material for engine applications is the AlSi9Cu3 alloy. This alloy has a good castability, excellent machinability, medium strength, and low specific weight. The study was focused on the investigation of the effect of the solution heat treatment on the microstructure and mechanical properties of the alloy (strength - Rm, hardness - HBS). The temperatures of the solution heat treatment were 505°C, 515°C, and 525°C± 5°C and the solution time rangedfrom 0 to 32 h (0, 2, 4, 8, 16, and 32 h). Alloy AlSi9Cu3 contained α-matrix, eutectic silicon, and other Fe- and Cu-rich phases with different morphology (needle-like, Chinese script, skeleton-like, blocky, etc.). The results obtained revealed the relation between the mechanical properties and the morphologies ofthe eutectic silicon and thepredominant copper-rich phase Al-Al2Cu-Si during the solution treatment.Сплав AlSi9Cu3 является одним из матери­алов, широко используемых в двигателестроении. Он имеет хорошую жидко-текучесть, отличную обрабатываемость, среднюю прочность и низкий удельный вес. Основное внимание в данном исследовании было направлено на исследование влияния гомогенизации на микроструктуру и механические свойства этого сплава (прочность исходного материала Кт, твердость НВХ). Обработка проводилась при температурах 505, 515 и 525°С± 5°С, длительность обработки колебалась в пределах 0...32 ч (0, 2, 4, 8, 16 и 32 ч). Сплав AlSi9Cu3 содержал α-матрицу, эвтектический кремний и дру­гие фазы, богатые железом и медью, име­ющие различную структуру (игольчатую, иероглифоподобную, ажурную, глыбообраз­ную и т.п.). Полученные результаты пока­зали существование зависимости между механическими свойствами и морфологиями эвтектического кремния и богатой медью Al-Al2Cu-Si-фазы, преобладающей во время гомогенизации

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

Determining the optimal solution treatment temperature of aluminum cast alloys by using quantitative analysis

Heat treatment of aluminum casts is necessary for achieving the desired properties of casts. Heat treatment caused changes in microstructure and substructure of materials and therefore it is necessary to control which changes are sufficient and which are insufficient. Morphology (shape, size and distribution) of microstructural features influence the properties of cast rapidly. Contribution describes influence of the heat treatment marking T4 - solution treatment in dependence on temperature (505, 515 a 525 °C) and holding time (2, 4, 8, 16 a 32 hour) on structure (α–phase, eutectic silicon, intermetallic phases) and mechanical properties (ultimate tensile strength - UTS and Brinell hardness - HBW) of A226 cast alloy. This cast alloy is made out of secondary aluminum. Secondary aluminum alloys are made of aluminum scrap. About 70 % of such material are used in the manufacture of casts. Therefore the strictly microstructure control of experimental material before and after heat treatment is necessary for declaration of cast properties. Nowadays manufacturers use the methods of quantitative analysis for quick control of microstructural features. This work present some of them

Microstructural features evaluation of age-hardened A 226 cast alloy by image analysis

Age-hardening provides one of the most widely used mechanisms for the strengthening of aluminum alloys. The age-hardening involves three steps: solution treatment, quenching and aging. The temperature of solution treatment and aging is very important in order to reach desired properties of castings. The optimum temperature of solution treatment and aging led to formation microstructural features in form which does not lead to decreasing properties, but increasing ones. The major micro-structural features in A 226 cast alloys which are responsible for increasing properties are: eutectic Si particles, Cu-rich phases, Fe-rich phases and porosity. The increase of properties depends on morphology, size and volume of microstructural features. In order to assess age-hardening influence on microstructural features in A226 cast alloys were used as possibilities of evaluation by means of image analysis. Quantitative analysis decelerate changes in microstructure includes the spheroidization and coarsening of eutectic silicon, gradual disintegration, shortening and thinning of Fe-rich intermetallic phases, the dissolution of precipitates and the precipitation of finer hardening phase (Al2Cu) further increase in the hardness and tensile strength in the alloy. Changes of mechanical properties were measured in line with STN EN ISO

Quality control of cylinder head casting

New challenges for the Aluminium alloys used for the production of castings for automotive engine components result from an evolutionary trend of internal combustion engines towards higher specific power output. Cylinder heads, in particular, have to withstand higher operating temperature and stress levels. Present work describes quality control of microstructure (Si-morphologhy and Si-size) and mechanical properties (UTS, elongation, Brinell hardness) of cylinder head casting as effect of different T6 heat treatment (solution heat treatment time - 2, 3, 4, 5, 6, 7 hours). The data obtained from this study will be used to improve process control, and to help the selection of heat treatment of the casting for future products

Self-Hardening AlZn10Si8Mg Aluminium Alloy as an Alternative Replacement for AlSi7Mg0.3 Aluminium Alloy

This article deals with the fatigue properties of newly used AlZn10Si8Mg aluminium alloy where the main aim was to determine the fatigue strength and compare it with the fatigue strength of AlSi7Mg0.3 secondary aluminium alloys which is used in the automotive industry for cyclically loaded components. AlZn10Si8Mg aluminium alloy, also called UNIFONT 90, is self-hardening (without heat treatments), which contributes to economic efficiency. This is one of the main reasons why is compared, and may be an alternative replacement for AlSi7Mg0.3 alloy which is heat treated to achieve required mechanical properties. The experiment results show that the fatigue properties of AlZn10Si8Mg alloy are comparable, if not better, than AlSi7Mg0.3 alloy. Fatigue properties of AlZn10Si8Mg alloy are achieved after seven days of natural ageing, immediately after casting and achieving value of fatigue strength is caused by structural components formed during solidification of the melt

Effect of laser surface treatment on the quality of microstructure in recycled Al-Zn-Si cast alloy

Recycled Al-Zn-Si casting alloys can often be used in new cast products for mechanical engineering, in hydraulic castings, textile machinery parts, cable car components or big parts without heat treatment. Improved mechanical properties and favourable of recycled microstructure of Al-alloys can often significantly increase the lifetime of casting and reduce costs for fuel and reduction of environmental loading. The paper is focused on using one of possible technologies that provide increased mechanical properties of recycled aluminium cast alloys for automotive industry, and that is laser surface hardening. For study was used recycled AlZn10Si8Mg cast alloy. The effect of laser beam Nd: YAG lasers BLS 720 was evaluated with the laser power 50 W and 80 W on the surface of samples. The final microstructure of aluminium alloys depend on the laser process parameters. The changes of microstructure as a grain refinement of the microstructure after laser surface hardening was observed by using classical techniques of etching and deep etching with concentrated HCl. Microstructure was evaluated on an optical microscope Neophot 32 and SEM

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

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