Submitted work deals with the analysis of reoxidation processes for aluminium alloys. Due to the aluminium high affinity to the oxygen, the oxidation and consequently reoxidation will occur. Paper focuses on the gating system design in order to suppress and minimize reoxidation processes. Design of the gating system is considered as one of the most important aspect, which can reduce the presence of reoxidation products - bifilms. The main reason for the reoxidation occurrence is turbulence during filling of the mold. By correctly designing the individual parts of gating system, it is possible to minimize turbulence and to ensure a smooth process of the mold filling. The aim of the work is an innovative approach in the construction of gating system by using unconventional elements, such as a naturally pressurized system or vortex elements. The aim is also to clarify the phenomenon during the gating system filling by visualization with the aid of ProCAST numerical simulation software. ProCAST can calculate different indicators which allow to better quantify the filling pattern.
The paper deals with the impact of technological parameters on the heat transfer coefficient and microstructure in AlSi12 alloy using
squeeze casting technology. The casting with crystallization under pressure was used, specifically direct squeeze casting method. The goal
was to affect crystallization by pressure with a value 100 and 150 MPa. The pressure applied to the melt causes a significant increase of
the coefficient of heat transfer between the melt and the mold. There is an increase in heat flow by approximately 50% and the heat
transfer coefficient of up to 100-fold, depending on the casting conditions. The change in cooling rate influences the morphology of the
silicon particles and intermetallic phases. A change of excluded needles to a rod-shaped geometry with significantly shorter length occurs
when used gravity casting method. By using the pressure of 150 MPa during the crystallization process, in the structure can be observed an
irregular silica particles, but the size does not exceed 25 microns.
The paper presents experimental results of creep and low cycle fatigue (LCF) tests carried out on the as-received cast aluminium alloys with different chemical composition and porosity. The test programmes contain creep investigations under step-increased stresses at different temperatures, and cyclic plasticity under different strain amplitudes and temperatures.
The research described in this contribution is focused on fractographic analysis of the fracture area of newly developed eutectic silumin type AlSi9NiCuMg0.5 (AA 4032), which was developed and patented by a team of staff of the Faculty of Mechanical Engineering. The paper presents determination of the cause of casting cracks in operating conditions. Fractographic analysis of the fracture area, identification of the structure of the casting, identification of structural components on the surface of the fracture surface and chemical analysis of the material in the area of refraction were performed within the experiment. Al-Si alloys with high specific strength, low density, and good castability are widely used in pressure-molded components for the automotive and aerospace industries. The results shown that the inter-media phases Fe-Al and Fe-Si in aluminium alloys lead to breakage across the entire casting section and a crack that crossed the entire cross section, which was confirmed by EDS analysis.
The paper presents results of bend tests at elevated temperatures of aluminium alloy EN AC-44200 (AlSi12) based composite materials
reinforced with aluminium oxide particles. The examined materials were manufactured by squeeze casting. Preforms made of Al2O3
particles, with volumetric fraction 10, 20, 30 and 40 vol.% of particles joined with sodium silicate bridges were used as reinforcement. The
preforms were characterised by open porosity ensuring proper infiltration with the EN AC-44200 (AlSi12) liquid alloy. The largest
bending strength was found for the materials containing 40 vol.% of reinforcing ceramic particles, tested at ambient temperature. At
increased test temperature, bending strength Rg of composites decreased in average by 30 to 50 MPa per 100°C of temperature increase.
Temperature increase did not significantly affect cracking of the materials. Cracks propagated mainly along the interfaces particle/matrix,
with no effect of the particles falling-out from fracture surfaces. Direction of cracking can be affected by a small number of
agglomerations of particles or of non-reacted binder. In the composites, the particles strongly restrict plastic deformation of the alloy,
which leads to creation of brittle fractures. At elevated temperatures, however mainly at 200 and 300°C, larger numbers of broken,
fragmented particles was observed in the vicinity of cracks. Fragmentation of particles occurred mainly at tensioned side of the bended
specimens, in the materials with smaller fraction of Al2O3 reinforcement, i.e. 10 and 20 vol.%.
The paper deals with squeeze casting technology. For this research a direct squeeze casting method has been chosen. As an experimental material, the AlSi12 and AlSi7Mg0.3 alloys were used. The influence of process parameters variation (pouring temperature, mold temperature) on mechanical properties and structure will be observed. For the AlSi7Mg0.3 alloy, a pressure of 30 MPa was used and for the AlSi12 alloy 50 MPa. The thicknesses of the individual walls were selected based on the use of preferred numbers and series of preferred numbers (STN ISO 17) with the sequence of 3.15 mm, 4 mm, 5 mm, 6.3 mm and 8 mm. The width of each wall was 22 mm and length 100 mm. The mechanical properties (Rm, A5) for individual casting parameters and their individual areas of different thicknesses were evaluated. For the AlSi7Mg0.3 alloy, the percentage increase of the tensile strength was up to 37% and the elongation by 400% (at the 8 mm thickness of the casting). For the AlSi12 alloy, the strength increased from 8 to 20% and the tensile strength increased from 5 to 85%. The minimum thickness of the wall to influence the casting properties by pressure was set to 5 mm (based on the used casting parameters). Due to the effect of the pressure during crystallization, a considerable refinement and uniformity of the casting structure occured, also a reduction in the size of the eutectic silicate-eliminated needles was observed.
The article discusses the weldment to casting conversion process of rocker arm designed for operation in a special purpose vehicle to
obtain a consistency of objective functions, which assume the reduced weight of component, the reduced maximum effort of material
under the impact of service loads achieved through topology modification for optimum strength distribution in the sensitive areas, and the
development of rocker arm manufacturing technology. As a result of conducted studies, the unit weight of the item was reduced by 25%,
and the stress limit values were reduced to a level guaranteeing safe application.
The article presents the analysis of properties of the high-strength AlZnMgCu (abbr AlZn) aluminium alloy and estimates possibilities of
its application for responsible structures with reduced weight as an alternative to iron alloy castings. The aim of the conducted studies was
to develop and select the best heat treatment regime for a 7xx casting alloy based on high-strength materials for plastic working from the
7xxx series. For analysis, wrought AlZnMgCu alloy (7075) was selected. Its potential of the estimated as-cast mechanical properties
indicates a broad spectrum of possible applications for automotive parts and in the armaments industry. The resulting tensile and fatigue
properties support the thesis adopted, while the design works further confirm these assumptions.
The paper deals with the impact of technological parameters on the mechanical properties and microstructure in AlSi12 alloy
using squeeze casting technology. The casting with crystallization under pressure was used, specifically direct squeeze
casting method. The goal was to affect crystallization by pressure with a value 100 and 150 MPa. From the experiments we
can conclude that operating pressure of 100 MPa is sufficient to influence the structural characteristics of the alloy AlSi12.
The change in cooling rate influences the morphology of the silicon particles and intermetallic phases. A change of excluded
needles to a rod-shaped geometries with significantly shorter length occurs when used gravity casting method. At a pressure
of 100 MPa was increased of tensile strength on average of 20%. At a pressure of 150 MPa was increased of tensile strength
on average of 30%. During the experiment it was also observed, that increasing difference between the casting temperature
and the mold temperature leads to increase of mechanical properties.
The present paper investigates the effects of variable-amplitude loads on fatigue crack growth rates for the 2024-T3 aluminium alloy on the basis of microfractographic analyses and its capacity to reconstruct load-time histories of failed components. For this purpose, there were applied three different variable-amplitude load sequences with single and multiple overloads and underloads. Subsequently, images of fatigue striations on components’ fracture surfaces were examined. The aforementioned loads were employed when simulating fatigue crack behaviour in aeronautical alloys.
The article presents the effect of rotational and travelling speed and down force on the spindle torque acting on the tool in Friction Stir Processing (FSP) process. The response surface methodology (RSM) was applied to find a dependence combining the spindle torque acting on the tool with the rotational speed, travelling speed and the down force. The linear and quadratic models with interaction between parameters were used. A better fitting was achieved for a quadratic model. The studies have shown that the increase in rotational speed causes a decrease in the torque while the increase in travelling speed and down force causes an increase in the torque. The tests were conducted on casting aluminium alloy AlSi9Mg. Metallography examination has revealed that the application of FSP process results in a decrease in the porosity in the modified material and microstructure refining in the stir zone. The segregation of Si and Fe elements was evident in the parent material, while in the friction stir processed area this distribution was significantly uniform.
An attempt was made to determine phase composition of commercial aluminium alloys using X-ray diffraction. Samples for phase composition analysis were selected from the group of aluminium alloys covered by the EN 573-3:2013 standard [1]. Representative samples were taken from eight groups of alloys with different chemical composition (at least one sample from each group). The diffraction intensity was measured with a standard X-ray diffractometer in Bragg-Brentano geometry in a way that allowed identification of the weakest diffraction peaks. As a results of the performed research it has been shown that X-ray phase analysis can be used to identify the matrix of aluminium alloys, Si and crystalline intermetallic phases such as Mg2Si, Al93.38Cu6.02Fe24Si16.27, Al4.01MnSi0.74, MgZn2, Al17(Fe3.2Mn0.8)Si2, Al65Cu20Fe15, and Cu3Mn2Al. The detectability limit of the above-mentioned phases is better than 0.5%. The research has also shown that X-ray phase analysis is applicable in the investigation of phase transformations taking place in aluminium alloys.
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