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In this study T6 heat treated 6063 aluminum alloys were used as substrate material. In order to form a bond between the substrate and the main coating, all samples were coated with Ni-Cr-Al powders. 8 wt% Yttria Stabilized Zirconia powders (YSZ) were coated with plasma spray technique. Thickness of YSZ was 150 μm and bond coating was 36 m. XRD and SEM-EDS analyses were performed to characterize the coating layers. These YSZ coated and uncoated samples were subjected to wear testing under different spindle speed, loading and working distance. Wear test results were compared with the kinetic friction coefficients and weight loss values. Wear marks on YSZ coated and uncoated samples were investigated by SEM analysis. By coating with plasma spray technique, the wear resistance of Al alloys was increased without changing the friction coefficient. It was found that spindle speed had significant effect over the wear properties than the load applied. By YSZ coating, wear properties were increased 10 times.

A356 is one of the widely used aluminium casting alloy that has been used in both sand and die casting processes. Large amounts of scrap metal can be generated from the runner systems and feeders. In addition, chips are generated in the machined parts. The surface area with regard to weight of chips is so high that it makes these scraps difficult to melt. Although there are several techniques evolved to remedy this problem, yet the problem lies in the quality of the recycled raw material. Since recycling of these scrap is quite important due to the advantages like energy saving and cost reduction in the final product, in this work, the recycling efficiency and casting quality were investigated. Three types of charges were prepared for casting: %100 primary ingot, %100 scrap aluminium and fifty-fifty scrap aluminium and primary ingot mixture were used. Melt quality was determined by calculating bifilm index by using reduced pressure test. Tensile test samples were produced by casting both from sand and die moulds. Relationship between bifilm index and tensile strength were determined as an indication of correlation of melt quality. It was found that untreated chips decrease the casting quality significantly. Therefore, prior to charging the chips into the furnace for melting, a series of cleaning processes has to be used in order to achieve good quality products.

Turbulent filling of a mould is one of the ways to introduce extrinsic defects into the cast part that could deteriorate many properties of any casting. The turbulence can be easily eliminated by counter gravity casting. In gravity casting, tapered downsprue, tapered runner is needed such that the mould cavity is filled counter-gravity from the bottom which is the only best way to eliminate turbulence during filling. Tilt casting method also exists which has the potential to quiescently transfer the liquid into the mould cavity. In this work, gravity and tilt casting methods were used to evaluate the tensile properties of Nb grain refined 206 alloy. Three different Nb contents were investigated: 0.025, 0.05 and 0.1 wt% ratios and it was found that 0.05 wt% revealed the highest tensile properties. On the other hand, when the intrusion of surface folded oxides was eliminated during filling, it was found that mechanical properties were increased significantly, and particularly, the toughness was increased by two folds when tilt casting was applied compared to gravity casting. [ABSTRACT FROM AUTHOR]

Aluminum alloys are widely used in the industry thanks to its many advantages such as light weight and high strength. The use of this material in the market is increasing day by day with the developing technology. Due to the high energy inputs in the primary production, the use of secondary ingots by recycling from scrap material are more advantageous. However, the liquid metal quality is quite important in the use of secondary aluminum. It is believed that the quality of recycled aluminum is low, for this purpose, many liquid metal cleaning methods and test methods are used in the industry to assess the melt cleanliness level. In this study, it is aimed to examine the liquid metal quality in castings with varying temperature using K mold. A206 alloy was used, and the test parameters were selected as: (i) at 725 °C, 750 °C and 775 °C casting temperatures, (ii) different hydrogen levels. The hydrogen level was adjusted as low, medium and high with degassing, as-cast, and upgassing of the melt, respectively. The liquid metal quality of the cast samples was examined by the K mold technique. When the results were examined, it was determined that metal K values and the number of inclusions were high at the as-cast and up-gas liquid with increasing casting temperatures. It has been understood that the K mold technique is a practical method for the determination of liquid metal quality, if there is no reduced pressure test machine available at the foundry floor. [ABSTRACT FROM AUTHOR]

In this work, 25 wheels were cast with three different grain refiners: Al5Ti1B, Al3Nb1B and MTS 1582. Samples were machined from the wheels to check the mechanical properties. It was found that Nb grain refinement had the lowest grain size (260 mm) and highest tensile properties (yield strength of 119-124 MPa and ultimate tensile strength of 190-209 MPa). Al5Ti1B and MTS 1582 revealed quite similar results (110 MPa yield and 198 MPa ultimate tensile strength). The fading of the grain refining effect of Al5TiB1 master alloy was observed in both Nb and Ti added castings whereas during the investigated time interval, the fading was not observed when MTS 1582 was used. [ABSTRACT FROM AUTHOR]

The solubility of Fe in aluminium alloys is known to be a problem in the casting of aluminium alloys. Due to the formation of various intermetallic phases, the mechanical properties decrease. Therefore, it is important to determine the formation mechanisms of such intermetallic. In this work, A360 alloy was used, and Fe additions were made. The alloy was cast into the sand and die moulds that consisted of three different thicknesses. In this way, the effect of the cooling rate was investigated. The holding time was selected to be 5 hours and every hour, a sample was collected from the melt for microstructural analysis. Additionally, the melt quality change was also examined by means of using a reduced pressure test where the bifilm index was measured. It was found that the iron content was increased after 2 hours of holding and the melt quality was decreased. There was a correlation between the duration and bifilm index. The size of AlSi-Mn-Fe phases was increased in parallel with the bifilm content regardless of the iron content. [ABSTRACT FROM AUTHOR]

Aluminum and its alloys are one of the most favored metal-based materials for engineering applications that require lightweight materials. On the other hand, composites are getting more preferable for different kinds of applications recently. Boron nitride nanotubes (BNNTs) are one of the excellent reinforcement materials for aluminum and its alloys. To enhance mechanical properties of aluminum, BNNTs can be added with different processes. BNNT reinforced aluminum matrix composites also demonstrate extraordinary radiation shielding properties. This study consists of BNNT reinforced aluminum matrix composite production performed by casting method. Since wetting of BNNT in liquid aluminum is an obstacle for casting, various casting techniques were performed to distribute homogeneously in liquid aluminum. Different methods were investigated in an aim to incorporate BNNT into liquid method as reinforcement. It was found that UTS was increased by 20% and elongation at fracture was increased by 170% when BNNT was preheated at 800oC for 30 minutes. [ABSTRACT FROM AUTHOR]

Casting is the most economical way of producing parts for many industries ranging from automotive, aerospace to construction towards small appliances in many shares. One of the challenges is the achievement of defect-free cast parts. There are many ways to do this which starts with calculation and design of proper runner system with correct size and number of feeders. The first rule suggests starting with clean melt. Yet, rejected parts can still be found. Although depending on the requirement from the parts, some defects can be tolerated, but in critical applications, it is crucial that no defect should exist that would deteriorate the performance of the part. Several methods exist on the foundry floor to detect these defects. Functional safety criteria, for example, are a must for today's automotive industry. These are not compromised under any circumstances. In this study, based on the D-FMEA (Design Failure Mode and Effect Analysis) study of a functional safety criterion against fuel leakage, one 1.4308 cast steel function block, which brazed-on fuel rail port in fuel injection unit, was investigated. Porosity, buckling, inclusion and detection for leak were carried out by non-destructive test (NDT) methods. It was found that the best practice was the CT-Scan (Computed Tomography) for such applications. [ABSTRACT FROM AUTHOR]

Production of the defect-free casting of aluminium alloys is the biggest challenge. Porosity is known to be the most important defect. Therefore, many cast parts are subjected to several non-destructive tests in order to check their acceptability. There are several standards, yet, the acceptance limit of porosity size and distribution may change according to the customer design and requirements. In this work, the aim was targeted to evaluate the effect of size, location, and distribution of pores on the tensile properties of cast A356 alloy. ANSYS software was used to perform stress analysis where the pore sizes were changed between 0.05 mm to 3 mm by 0.05 mm increments. Additionally, pore number was changed from 1 to 5 where they were placed at different locations in the test bar. Finally, bifilms were placed inside the pore at different sizes and orientations. The stress generated along the pores was recorded and compared with the fracture stress of the A356 alloy. It was found that as the bifilm size was getting smaller, their effect on tensile properties was lowered. On the other hand, as bifilms were larger, their orientation became the dominant factor in determining the fracture. [ABSTRACT FROM AUTHOR]

Porosity is one of the major problems in casting operations and there are several discussions in the literature about the porosity formation in aluminum castings. Bifilms are the defects that are introduced into the melt by turbulence. They can be detected with reduced pressure test and presented numerically by measuring bifilm index. The measure of bifilm index is the sum of total oxide length given in millimeters from the cross-section of reduced pressure test sample solidified under 0.01 MPa. In this work, low pressure die casting (LPDC) unit was built in an attempt to enhance the producibility rate. The unit consists of a pump housing that was placed inside the melt in the melting furnace where the pressure was applied instead of the whole melt surface. It was observed that the melt quality of A356 alloy was deteriorated over time which had led to higher porosity. This was attributed to the increased oxide thickness of the bifilm by the consumption of air in between the folded oxides. A relationship was found between bifilm index and pore formation. [ABSTRACT FROM AUTHOR]

Recyclability is one of the great features of aluminium and its alloys. However, it has been typically considered that the secondary aluminium quality is low and bad. This is only because aluminium is so sensitive to turbulence. Uncontrolled transfer and handling of the liquid aluminium results in formation of double oxide defects known as bifilms. Bifilms are detrimental defects. They form porosity and deteriorate the properties. The detection and quantification of bifilms in liquid aluminium can be carried out by bifilm index measured in millimetres as an indication of melt cleanliness using Reduced Pressure Test (RPT). In this work, recycling efficiency and quality change of A356 alloy with various Ti additions have been investigated. The charge was recycled three times and change in bifilm index and bifilm number was evaluated. It was found that when high amount of Ti grain refiner was added, the melt quality was increased due to sedimentation of bifilms with Ti. When low amount of Ti is added, the melt quality was degraded. [ABSTRACT FROM AUTHOR]

Aluminium alloys are one of the preferred materials especially for land and air transportation because of their high strength and lowdensity properties. Although production using casting method is economical yet it has some disadvantages. Shrinkage which is occurred due to the density difference between the solid and liquid metal is prevented by feeders which need to be calculated. Liquid metal should be transferred to the mould without any turbulence. As a result, sprues are needed to be designed precisely. On the other hand, aluminium alloys can also be shaped by forging at semi-solid temperatures. There are some advantages compared to the traditional forging methods of improving die life due to the lower tonnage values. In this study, semi-solid produced 7075 aluminium alloy die filling capabilities were investigated. To achieve semisolid structure strain induced melt activated method (SIMA) was used. The desired structure was achieved at 635 °C and 30 minutes of duration of heat treatment. After determining the optimum parameters, metallographic analysis, density calculations, porosity distribution and tensile tests were carried out. It was found that the reproducibility of SIMA produced 7075 alloy was quite low. A proper tensile test result was achieved only 7 of the total 15 tests and the mean value was 386 MPa. The main reason for this scattered in mechanical properties could be the chemical composition of the alloy and the rapid solidification of the liquid eutectic phases. It is important to define the best fitting process parameters and controlling them precisely will be the most important factors for future studies. [ABSTRACT FROM AUTHOR]

Light weight, low density with high mechanical properties and corrosion resistance, aluminum is the most important material and is commonly used for high performance applications such as aerospace, military and especially automotive industries. The researchers who participate in these industries are working hard to further decrease the weight of end products according to legal boundaries of greenhouse gases. A lot of research was undertaken to produce thin sectioned aluminum parts with improved mechanical properties. Several alloying element addition were investigated. Yet, nowadays aluminum has not met these expectations. Thus, composite materials, particularly metal matrix composites, have taken aluminum's place due to the enhancement of mechanical properties of aluminum alloys by reinforcements. This paper deals with the overview of the reinforcements such as SiC, Al2O3 and graphene. Graphene has recently attracted many researcher due to its superior elastic modulus, high fatigue strength and low density. It is foreseen and predicted that graphene will replace and outperform carbon nanotubes (CNT) in near future. [ABSTRACT FROM AUTHOR]

Al-4.5Cu alloys are widely used in aerospace industries due to their low weight and high mechanical properties. This group of aluminium alloys is known as 2xx series and exhibits the highest mechanical properties however this alloy is known to suffer from feedability and high tendency for hot tearing. Al-Si alloys (3xx) have improved fluidity and better feedability particularly by several modifications such as Ti, B or Sr. Eutectic temperature is decreased and mechanical properties can be enhanced. Yet, the strength values of this alloy group cannot reach the values of 2xx series. Therefore, in this study, the effect of Ag addition on the fluidity of Al-4.5Cu alloy has been investigated. Standard size spiral mould was used. The casting temperature was selected to be 770oC. Five castings were made and Weibull statistical approach was used to evaluate the results. In addition, coating of the die with BN was also investigated. It was found that Ag addition and BN coating of the die revealed the most reproducible, reliable and high fluidity values. [ABSTRACT FROM AUTHOR]

In situ composites have been studied mainly to eliminate wettability, porosity and non-uniform distribution of particulate problems in composite materials. Al-Mg2Si alloy are preferred choice of such group of alloys owing to the combination of light weight and improved mechanical properties. The morphology of Mg2Si is one of the key parameters for the wear properties. In this work, squeezed casting method was used to produce samples where porosity was aimed to be reduced and morphology of Mg2Si was altered. In addition, the wear properties of in situ A380-Mg2Si were investigated. It was found that as squeeze pressure was increased, porosity and size of Mg2Si was decreased and wear rate was increased. [ABSTRACT FROM AUTHOR]

Hydrogen in aluminum alloy melts leads to porosity, generally considered to be the most serious defect affecting both static and dynamic properties of structural aluminum castings. In order to study these effects, an investigation has been undertaken to examine the A356 alloy that is gravity die cast and directionally solidified. Castings were produced with as-molten metal and degassed metal, and with metal up-gassed by various treatments. Hydrogen content during melt treatment was measured with ALSPEK H,® a device based on electrochemical principles. Porous disc filtration apparatus (PoDFA) and reduced pressure tests (RPT) were performed in parallel with casting experiments to assess melt quality. The effect of hydrogen content and melt cleanliness on the amount, size, shape, and location of porosity was characterized, and the results show that amongst all the upgassing methods used, up-gassing with wood and Ar-water vapor mixture is the most efficient. Pore size and shape factor increased with increasing distance from the chill. [ABSTRACT FROM AUTHOR]