Paper present a thermal analysis of laser heating and remelting of EN AC-48000 (EN AC-AlSi12CuNiMg) cast alloy used mainly for casting pistons of internal combustion engines. Laser optics were arranged such that the impingement spot size on the material was a circular with beam radius rb changes from 7 to 1500 m. The laser surface remelting was performed under argon flow. The resulting temperature distribution, cooling rate distribution, temperature gradients and the depth of remelting are related to the laser power density and scanning velocity. The formation of microstructure during solidification after laser surface remelting of tested alloy was explained. Laser treatment of alloy tests were perform by changing the three parameters: the power of the laser beam, radius and crystallization rate. The laser surface remelting needs the selection such selection of the parameters, which leads to a significant disintegration of the structure. This method is able to increase surface hardness, for example in layered castings used for pistons in automotive engines.
The chosen, typical causes of quality defects of cast-iron „alphin” rings embedded in aluminum cast are being presented in this paper. Diffusive joint of those inserts with the pistons casts is being used, due to extreme work conditions of destructive influence of the fuel mix and variable thermo-mechanical loads, which reign in the combustion motor working chamber.
In the dissertation it has been shown, that so called “time-thermal treatment” (TTT) of the alloy in liquid state as overheating the metal with around 250o C above Tliq. and detailing it in temperature for 30 to 40 minutes has the influence on changing the crystallization parameters (Tliq., TEmin. , TEmax., TE(Me), TSol.). It was ascertained, that overheating the AlSi17Cu5Mg alloy substantially above Tliq. results with microcrystalline structure. Evenly distributed in the eutectic warp primeval silicon crystals and supersaturated with alloying additives of base content (Cu, Mg, Fe) of α(Al) solution, ensures not only increase durability in ambient temperature, but also at elevated temperature (250o C), what due to it’s use in car industry is an advantage.
In this study, metal matrix composite materials containing melt-spun Al-20Si-5Fe alloys and boron carbide was produced by high energy ball milling and then hot pressing at 200 MPa pressure and 450°C. Mechanical and microstructural characterizations were performed by using an optical microscopy, X-Ray diffractometer, and dynamic microhardness tester. It was observed that boron carbide particles were homogenously distributed in the microstructure and values of microhardness and elastic modules were averagely 830 MPa and 42 GPa, respectively.
This paper considers the assessment of attenuation in aluminium alloys castings and in cast iron prepared by gravity casting method and by casting under pressure. The issue of ultrasound attenuation is important in setting the conditions of non-destructive (NDT) testing, especially in casted materials. The characteristics of the ultrasonic technique and ultrasonic attenuation and the calculation of the attenuation and the velocity of ultrasound are presented in the theoretical part of this paper. For experimental measurements, cylindrical castings from AlSi alloy (a hypoeutectic alloy with a silicon content of about 7% - AlSi7 and a eutectic alloy with a silicon content of about 12% - AlSi12) and from grey and ductile cast iron were made. The ultrasonic records of the casting control, the calculation of ultrasound attenuation for individual samples are listed and described in the experimental part. The evaluation of measurements and comparison of calculated ultrasound attenuation is at the end of this article.
The paper presents tribological properties of A390.0 (AlSi17Cu5Mg) alloy coupled in abrasive action with EN-GJL-350 grey cast-iron. The silumin was prepared with the use of two different technologies which differed in terms of cooling speed. In the first case the alloy was modified with foundry alloy CuP10 and cast to a standard tester ATD and in case of second option the modified alloy was cast into steel casting die. Due to different speed of heat removal the silumins varied in structure, particularly with size of primary crystals of silicon and their distribution in matrix which had a significant influence of friction coefficient in conditions of dry friction.
This paper presents the results of hypoeutectic 226 grade alloy as well as prepared on its basis Al-Si alloy containing Cr, V and Mo. The additives tested were added as AlCr15, AlV10 and AlMo8 master alloys. Alloys tested were poured into DTA sampler as well as using pressure die casting. An amount of Cr, V and Mo additives in alloy poured into DTA sampler comprised within the range approximately 0.05-0.35%. Alloys to pressure die casting contained 0.05-0.20% Cr, V and Mo. The crystallization process was examined using the derivative thermal analysis (DTA). The microstructure of castings made in the DTA sampler as well as castings made with use of pressure die casting were examined. The basic mechanical properties of castings made using pressure die casting were defined too. It has been shown in the DTA curves of Al-Si alloy containing approximately 0.30 and 0.35% Cr, Mo, and V there is an additional thermal effect probably caused by a peritectic crystallization of intermetallic phases containing the aforementioned additives. These phases have a morphology similar to the walled and a relatively large size. The analogous phases also occur in pressure die casting alloys containing 0.10% or more additions of Cr, V and Mo. The appearance of these phases in pressure die casting Al-Si alloys coincides with a decrease in the value of the tensile strength Rm and the elongation A. It has been shown die castings made of Al-Si alloys containing the aforementioned additives have a higher Rm and A than 226 alloy.
With the use of differential scanning calorimetry (DSC), the characteristic temperatures and enthalpy of phase transformations were defined for commercial AlSi9Cu3 cast alloy (EN AC-46000) that is being used for example for pressurized castings for automotive industry. During the heating with the speed of 10oCmin-1 two endothermic effects has been observed. The first appears at the temperature between 495 oC and 534 oC, and the other between 555 oC and 631 oC. With these reactions the phase transformation enthalpy comes up as +6 J g-1 and +327 J g-1 . During the cooling with the same speed, three endothermic reactions were observed at the temperatures between 584 oC and 471 oC. The total enthalpy of the transitions is – 348 J g-1 . Complimentary to the calorimetric research, the structural tests (SEM and EDX) were conducted on light microscope Reichert and on scanning microscope Hitachi S-4200. As it comes out of that, there are dendrites in the structure of α(Al) solution, as well as the eutectic (β) silicon crystals, and two types of eutectic mixture: double eutectic α(Al)+β(Si) and compound eutectic α+Al2Cu+β.
The paper presents the results of studies on the effect of the AlSi17Cu5 alloy overheating to atemperature of 920°C and modification with phosphorus (CuP10) on the resultingmechanical (HB, Rm, R0.2) and plastic (A5 and Z) properties. It has been shown that, so-called, "timethermal treatment" (TTT) of an alloy in the liquid state, consisting inoverheating the metal to about 250°C above Tliq,holding at this temperature by 30 minutes improvesthe mechanical properties. It has also been found that overheating of alloy above Tliq.enhances the process of modification, resulting in the formation of fine-grain structure. The primary silicon crystals uniformly distributed in the eutectic and characteristics ofthe α(Al) solution supersaturated with alloying elements present in the starting alloy composition (Cu, Fe) provide not only an increase of strength at ambient temperature but also at elevated temperature (250°C).
The study presents the results of the application of a statistical analysis for the evaluation of the effect of high-melting additions introduced into a pressure cast Al-Si alloy on the obtained level of its proof stress Rp0.2. The base Al-Si alloy used for the tests was a typical alloy used for pressure casting grade EN AC-46000. The base alloy was enriched with high-melting additions, such as: Cr, Mo, V and W. The additions were introduced into the base Al-Si alloy in all the possible combinations. The content of the particular high-melting addition in the Al-Si alloy was within the scope of 0.05 to 0.50%. The investigations were performed on both the base alloy and alloy with the high-melting element additions. Within the implementation of the studies, the values of Rp0.2 were determined for all the considered chemical compositions of the Al-Si alloy. A database was created for the statistical analysis, containing the independent variables (chemical composition data) and dependent variables (examined Rp0.2 values). The performed statistical analysis aimed at determining whether the examined high-melting additions had a significant effect on the level of Rp0.2 of the Al-Si alloy as well as optimizing their contents in order to obtain the highest values of the Al-Si alloy's proof stress Rp0.2. The analyses showed that each considered high-melting addition introduced into the Al-Si alloy in a proper amount can cause an increase of the proof stress Rp0.2 of the alloy, and the optimal content of each examined high-melting addition in respect of the highest obtained value of Rp0.2 equals 0.05%.
In the dissertation it has been shown, that so called „time-thermal treatment” (TTT) of the alloy in liquid state, as overheating the metal with around 250o C above the Tliq. and detaining it in this temperature for around 30 minutes, improves the mechanical properties (HB, Rm, R0,2). It was ascertained, that overheating the AlSi17Cu5Mg alloy aids the modification, resulting with microcrystalline structure. Uniform arrangement of the Si primeval crystals in the warp, and α(Al) solution type, supersaturated with alloying elements present in the base content (Cu, Mg) assures not only increased durability in the ambient temperature, but also at elevated temperature (250o C), what is an advantage, especially due to the use in car industry.
The paper presents the results of the application of a statistical analysis to evaluate the effect of the chemical composition of the die casting Al-Si alloys on its basic mechanical properties. The examinations were performed on the hypoeutectic Al-Si alloy type EN AC-46000 and, created on its basis, a multi-component Al-Si alloy containing high-melting additions Cr, Mo, W and V. The additions were introduced into the base Al-Si alloy in different combinations and amounts (from 0,05% to 0,50%). The tensile strength Rm; the proof stress Rp0,2; the unit elongation A and the hardness HB of the examined Al-Si alloys were determined. The data analysis and the selection of Al-Si alloy samples without the Cr, Mo, W and V additions were presented; a database containing the independent variables (Al-Si alloy's chemical composition) and dependent variables (Rm; Rp0,2; A and HB) for all the considered variants of Al-Si alloy composition was constructed. Additionally, an analysis was made of the effect of the Al-Si alloy's component elements on the obtained mechanical properties, with a special consideration of the high-melting additions Cr, Mo, V and W. For the optimization of the content of these additions in the Al-Si alloy, the dependent variables were standardized and treated jointly. The statistical tools were mainly the multivariate backward stepwise regression and linear correlation analysis and the analysis of variance ANOVA. The statistical analysis showed that the most advantageous effect on the jointly treated mechanical properties is obtained with the amount of the Cr, Mo, V and W additions of 0,05 to 0,10%.
In the dissertation the data modeling has been shown for the data that regards the damages, which value is above zero. With the use of Weibull distribution, with prior regression and correlation analysis chosen parameters that defines the life time and failure level of two populations of AlSi17Cu5 were defined. The calculation sheet of reliability allows to create so called survival diagram, and on the basis of durability data the average warrantee can be determined, on the pre-exploitation period.
The paper concerns the problem of discontinuity in high pressure die castings (HPDC). The compactness of their structure is not perfect, as it is sometimes believed. The discontinuities present in these castings are the porosity as follow: shrinkage and gas (hydrogen and gas-air occlusions) origin. The mixed gas and shrinkage nature of porosity makes it difficult to identify and indicate the dominant source. The selected parameters of metallurgical quality of AlSi9Cu3 alloy before and after refining and the gravity castings samples (as DI - density index method), were tested and evaluated. This alloy was served to cast the test casting by HPDC method. The penetrating testing (PT) and metallographic study of both kinds of castings were realized. The application of the NF&S simulation system allowed virtually to indicate the porosity zones at risk of a particular type in gravity and high-pressure-die-castings. The comparing of these results with the experiment allowed to conclude about NF&S models validation. The validity of hypotheses concerning the mechanisms of formation and development of porosity in HPDC casting were also analyzed.
The impact of casting conditions on microstructure a and mechanical properties was described, especially for cast products from AlSi9Cu3 alloy. Particular attention was paid to the parameters of dendritic structure: DAS 1 and DAS 2. Selected mechanical properties (by static tension test) of test castings made using basic technologies of casting: GSC - gravity sand casting, GDC - gravity die-casting and HPDC - high-pressure die-casting, are presented for cast-on test bars and cast separately. Casts were made of the same alloy AlSi9Cu3. Fractures and the zone near the fracture (after static tension test) was subjected to VT - visual tests, PT - penetration tests and metallographic tests. The condition of porosity (fracture zone) was also assessed. The analysis of virtual results was performed using the NovaFlow & Solid system together with the database and they were compared to experimental tests. This way of validation was applied in order to assess the correlation between the local rate of cooling and the size of DAS for GSC, GDC and HPDC technologies. Finally, the correlation between the parameters of structure and mechanical properties with regard to the impact of porosity was signalized.
In this work, the effect of the microstructure on corrosion behavior of selected Mg- and Al-based as cast alloys, was evaluated. The electrochemical examinations were carried out, and then a morphology of corrosion products formed due to local polarization on materials surface, was analyzed. It was documented that the presence of Mg2Si phase plays an important role in the corrosion course of Mg-based alloy. A selective etching was observed in sites of Mg2Si precipitates having “Chinese script”- like morphology. Analogous situation was found for Al-based alloy, where the key role was played by cathodic θ-CuAl2 phase.
This paper deals with influence on segregation of iron based phases on the secondary alloy AlSi7Mg0.3 microstructure by chrome. Iron is the most common and harmful impurity in aluminum casting alloys and has long been associated with an increase of casting defects. In generally, iron is associated with the formation of Fe-rich phases. It is impossible to remove iron from melt by standard operations, but it is possible to eliminate its negative influence by addition some other elements that affect the segregation of intermetallics in less harmful type. Realization of experiments and results of analysis show new view on solubility of iron based phases during melt preparation with higher iron content and influence of chrome as iron corrector of iron based phases. By experimental work were used three different amounts of AlCr20 master alloy a three different temperature of chill mold. Our experimental work confirmed that chrome can be used as an iron corrector in Al-Si alloy, due to the change of intermetallic phases and shortening their length.
This paper deals with influence on segregation of iron based phases on the secondary alloy AlSi7Mg0.3 microstructure by nickel. Iron is the most common and harmful impurity in aluminum casting alloys and has long been associated with an increase of casting defects. In generally, iron is associated with the formation of Fe-rich intermetallic phases. It is impossible to remove iron from melt by standard operations. Some elements eliminates iron by changing iron intermetallic phase morphology, decreasing its extent and by improving alloy properties. Realization of experiments and results of analysis show new view on solubility of iron based phases during melt preparation with higher iron content and influence of nickel as iron corrector of iron based phases.
The research focused on the influence of the solution temperature on the structure of precipitation hardening multi-component hypoeutectic aluminium alloys. The AlSi8Cu3 and AlSi6Cu4 alloys were used in the study and were subjected to a thermal-derivative analysis. The chemical composition and crystallization of phases and eutectics shift the characteristic points and the corresponding temperatures to other values, which affect to, for instance, the solution temperature. The alloys were supersaturated at 475°C (according to the determined temperature (TSol) and 505°C for 1.5 hours. Aging was performed at 180°C for 5 hours. The Rockwell hardness measurement, metallographic analysis of alloys by means of light microscopy as well as chemical and phase analysis using scanning electron microscopy and X-ray crystallography were carried out on alloys. The use of computer image analysis enabled the determination of the amount of the current Al2Cu phase in the alloys before and after heat treatment.
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.
This paper deals with influence of chrome addition and heat treatment on segregation of iron based phases in the secondary alloy AlSi7Mg0.3 microstructure by chrome and heat treatment. Iron is the most common and harmful impurity in aluminum casting alloys and has long been associated with an increase of casting defects. In generally, iron is associated with the formation of Fe-rich intermetallic phases. It is impossible to remove iron from melt by standard operations, but it is possible to eliminate its negative influence by addition some other elements that affect the segregation of intermetallics in less harmful type or by heat treatment. Realization of experiments and results of analysis show new view on solubility of iron based phases during melt preparation with higher iron content and influence of chrome as iron corrector of iron based phases.