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Porosity plays an important role in the properties of powder metallurgy products and castings. Nowadays, there are several methods for determining porosity: optical microscopy, computed tomography, and density measurement according to Archimedes’ principle. The aim of this study is to present the advantages and disadvantages of different porosity testing methods and the relationships between the results. With conventional metallographic methods, only two-dimensional information about pores is obtained. The accuracy of a three-dimensional CT examination is significantly affected by the resolution, the quality of the image, and the evaluation process. The porosities of aluminum (AlSi7MgCu0.5) reduced pressure test samples with different densities were determined on 3D x-ray images with the evaluation software VGStudio MAX 3.3 and on 2D section x-ray images and the optical microscope images with the image analysis software ImageJ. The effect of morphological transformation of 3D images and the role of the region of interest volume and area under examination are also discussed.

The press and sinter method remains the standard among powder metallurgy processes for powdered stainless-steel materials. It delivers low cost, low oxidation rate, and adequate corrosion resistance. Furthermore, 17-4PH is a martensitic stainless-steel that is commonly used for high-strength and medium-ductility stainless steel parts. However, a few studies have investigated the press and sinter method for producing 17-4PH parts. This shortage is due to the high hardness (low compressibility) of 17-4PH powder. Thus, the main objective of this study is to evaluate the press and sinter method in terms of the manufacturing process, the influencing factors, and the theoretical basis of press and sinter methods in conjunction with metal injection molding technology for the production of 17-4PH parts. First, the literature and monographs are examined and summarized to cover the previous results, research progress, development trends, and applications of press and sinter method 17-4PH parts. Following the theoretical analysis, the practical investigation was conducted by producing parts with cold pressing from 800 to 1600 MPa, followed by sintering: the sintering temperature was 1200 °C for one hour under a protective vacuum atmosphere. ImageJ analysis was performed to measure the sinter density. The results showed an increase in relative sinter density from 84.43% to 96.43% for 800 and 1600 MPa, respectively, while the earlier results reached 93.47%. Overall, the press and sinter method enables the production of high-hardness 17-4PH parts with a high density, without using additives like lubricants, wax, or alloying elements.

In the present study, an electroless nickel (EN) plating method is applied for the coating of silicon carbide (SiC) particles. The particles of SiC(Ni) were added to the Sn–3.0Ag–0.5Cu matrix for the production of SAC305/SiC(Ni) composite by the powder metallurgy route. SAC305/xSi(Ni) composite was prepared by a planetary ball milling of the starting powder, followed by compacting and sintering. Nickel-coated silicon carbide particles and the lead-free solder matrix react together, forming different phases during sintering at temperature 200°C for 3 h. The microstructure, mechanical (compressive strength, microhardness, wettability, and porosity) and physical properties (density) of lead-free solder composite SAC305/SiC(Ni) were studied. The current research shows the successful application of electroless nickel (EN) plating method, and how nickel-coated SiC particles subsequently improve the mechanical properties and microstructure of lead-free solder.

In this paper, the effect of soldering technique and thermal shock test were investigated on SAC 305 solder joints, produced by 2 different solder methods, which are the most common solder material...

Good wetting, strong bonding and low electrical resistance are the most important properties of the solder in microelectronic packaging. Aim of this study was to improve the mechanical and wetting properties of commercially available lead-free solders. Different type and sized ceramic particles treated with different surface modification methods were added to lead-free SAC305 solder paste to form composites. The reinforcement particles were subjected to various surface modification processes. We made reflow soldering in the same way as in industrial application. Solder joints were formed between a novel designed test PCB board and microelectronic components. The mechanical properties of the composite joint were tested by microhardness measurement and shear test, while the microstructure and the IML layer were examined by scanning electron microscope.

The Sn-3.0Ag-0.5Cu solder alloy is a prominent candidate for the Pb-free solder, and SAC305 solder is generally employed in today’s electronic enterprise. In this study, the formation of intermetallic compounds (Cu6Sn5 and Ag3Sn) at the interface, average neighbour’s particle distance, and the morphological mosaic are examined by the addition of SiC and nickel-coated silicon carbide reinforcements within Sn-3.0Ag-0.5Cu solder. Results revealed that the addition of SiC and SiC(Ni) particles are associated with a small change to the average neighbor’s particle distance and a decrease of clustering rate to a certain limit of the Sn-3.0Ag-0.5Cu solder composites. Moreover, the development of the Cu6Sn5 and the structure of the Ag3Sn are improved with the addition of SiC and Ni coated SiC.

The kinetics of transformation of 5 w% TiB2 nano-particles (50 nm diameter) dispersed and pressed (1.5 GPa) in the of Ti matrix (150 µm diameter) into TiB nano-whiskers was studied as a function of temperature (800–900–1000 °C) and time (5–720 min) in 25 experiments in total, by vacuum sintering. The classical one-step Avrami kinetics does not properly describe this transformation due to the formation of oxide inhibitors from contaminants. However, the same results could be perfectly described by a complex Avrami kinetics supposing two parallel steps of transformations: i). fast transformation along the initially metallic Ti/TiB2 interface and ii). delayed transformation along contaminated Ti/TiB2 interface. Data for kinetic calculation was obtained by X-ray diffraction and Rietveld refinement on the sintered samples. Extrapolating the experimental results by the complex Avrami model beyond the measured temperature interval it was found that at and above about 1050 °C, the second step is missing due to the fast dissolution of oxide films in the beta-Ti matrix, leading to very fast kinetics.

The Sn–Ag–Cu (SAC) solders with low Ag or Cu content have been identified as promising candidates to replace the traditional Sn–Pb solder. In this study, an extensive discussion was presented on two major area of mechanical properties and microstructural investigation of SAC305 and SAC405. In this chapter, we study the composition, mechanical properties of SAC solder alloys and microstructure were examined by optical microscope and SEM and mechanical properties such as tensile tests, hardness test and density test of the lead solder alloys were explored. SAC305 and SAC405 alloys with different Ag content and constant Cu content under investigation and compare the value of SAC305 and SAC405. From this investigation, it was reported that tensile strength is increased, with an increase of Ag content and hardness and density were also increases in the same manner.

The Lead-free solders (SAC) with low Ag content have been identified as crucial solder to replace the traditional Sn–Pb solder. The main discussion was presented in two major area of microstructural investigation and mechanical properties of SAC305 and SAC405. Composition and microstructure of SAC solder alloys were investigated by an optical microscope and SEM (Scanning Electron Microscopy). Mechanical properties such as tensile tests and hardness test of the lead-free solder alloys have been tested in this research. Different Ag content and constant Cu content of lead-free solder has been considered in this investigation and compare the mechanical properties of SAC305 and SAC405 solders. From this investigation, tensile strength and hardness have been increased with increased of Ag content.

In the present article a 45Mo-45Cu-10Al2O3 (wt%) nano-composite was produced by mechanical alloying, shaped by cold pressing then by hot pressing at 950 °C. Our aim was to investigate the effect of different ball to powder ratio (BPR) on the particle size and shape, as well as on the material composition. Investigations were done with XRD, SEM and for hot pressed specimens Brinell hardness measurement. Lower BPR resulted in nano-sized crystallites in the powder, a homogenous phase distribution and higher BPR resulted in even smaller crystallite sizes, but with ZrO2 contamination from the milling equipment. The milling resulted in two separate fractions in the metallic phases separated by crystallite size, strain and lattice parameter. After hot pressing, the lower BPR powders developed a homogeneous, evenly distributed microstructure. Cu recrystallized during hot pressing, but still remained nanocrystalline, the crystallite size of Mo and α-Al2O3 decreased even more due to crystallite deformation and in the case of Mo, the lattice strain values indicates that recovery had also happened. The heating eliminated the crystal defects at highly strained areas and the subsequent cooling evened out the stresses in the respective metallic phases. The inner grain structure was revealed by etching, showing that α-Al2O3 particles congregated only at the Mo grain boundaries, but penetrated the Cu grains. The lattice strain values combined with the BSE images reveal that the Cu is the main matrix of the α-Al2O3 particles. The results indicate that the α-Al2O3 particles induced Particle Stimulated Nucleation (PSN) in the Cu explaining its moderate crystallite size increase. The hot pressed samples of higher BPR had higher ceramic (ZrO2 and α-Al2O3) content, resulting in higher hardness, but lower relative density (92.4%), compared to the samples of lower BPR, which reached 97.2% relative density and hardness still significantly higher than Mo Cu alloys.

According to the directives (RoHS and WEEE) adopted by the European Union, lead has been banned from the manufacturing processes because of its health and environmental hazards. Therefore, the development of lead-free solders is one of the most important research areas of the electronic industry. This paper investigates multicomponent Sn-Ag-Cu based lead-free solders with different compositions. The properties of the six-component Innolot (SAC+BiSbNi) and two low-Ag containing alloys were compared with the widespread used SAC307 solder. Microstructure investigations and X-ray diffraction measurements were performed to analyze and identify the formed phases, furthermore, tensile tests and microhardness measurements were executed to determine the mechanical properties of the examined solders.

Aluminum matrix composites were prepared by adding submicron sized WC particles into a melt of Al 1050 under mechanical stirring, with the scope to determine: (a) the most appropriate salt flux amongst KBF4, K2TiF6, K3AlF6and Na3AlF6for optimum particle wetting and distribution and (b) the maximum carbide volume fraction (CVF) for optimum response to sliding wear. The nature of the wetting agent notably affected particle incorporation, with K2TiF6providing the greatest particle insertion. A uniform aluminide (in-situ) and WC (ex-situ) particle distribution was attained. Two different sliding wear mechanisms were identified for low CVFs (≤1.5%), and high CVFs (2.0%), depending on the extent of particle agglomeration.

In this manuscript, correlations were searched for between pin misalignments relative to PCB bores and crack propagation after cyclic thermal shock tests in THT solder joints produced from lead-free solder alloys. In total, 7 compositions were examined including SAC solders with varying Ag, Cu and Ni contents. The crack propagation was initiated by cyclic thermal shock tests with 40°C / +125°C temperature profiles. Pin misalignments relative to the bores were characterized with three attributes obtained from one section of the examined solder joints. Cracks typically originated at the solder/pin or solder/bore interfaces and propagated within the solder. It was shown that pin misalignments did not have an effect on crack propagation, thus, the solder joints’ lifetime.

This work represents an interesting development in the detection and interpretation of crack evolution in through hole technology (THT) solder joints, which based on the development of general and common method. Serial sectioning is a useful method because it overcomes the problems associated with traditional two-dimensional metallographic techniques by providing information about (micro)structures in three-dimensions.In our work, serials sectioning with reconstruction method was utilized to visualize the 3D nature of cracks in through hole solder joint. Accurate quantitive analysis of the cracks, such as crack length, position and extension are presented with a help of the developed method: newly defined parameter and serial-cross sectioning method.

W and Cu can be found in separate phases in the W-Cu composites since these elements do not dissolve in each other neither in liquid nor in solid phase, but with mechanical alloying it is possible to produce nonequilibrium W-Cu alloys In this work the nanostructured W-Cu composites were produced by planetary ball milling. The nanostructured W-Cu powder was sintered on 900 °C and 950 °C with 50 MPa pressure applied. The meso- and microstructure of the W-Cu powder and the sintered samples, were investigated with SEM, TEM and XRD. After 50 h of milling, the size of the W crystallites was ~10 nm, and about 10% of the Cu was solved in the W matrix, producing a W-Cu nonequilibrium alloy layer on the surface of W nano crystallites. During sintering, the Cu atoms left from the W surface to the Cu phases, so the W-Cu nonequilibrium alloy layer disappeared. The size of the W crystallites – after 60 min of sintering on 950 °C - was around 170 nm, and the relative density was ~90% of the theoretical density.

The current investigation was conducted to understand the effect of 1wt. % silicon carbide (SiC) in the Sn–3.5Ag–0.5Cu (SAC305) lead-free solder alloy which was produced by the powder metallurgy method. A systematic investigation of the microstructure of the solidified composite solder along with its wetting behavior was carried out at different reflow temperatures (230°C–290°C). From microstructure investigation, it was clear that SiC ceramic particles influence the development of IMCs at the Cu–Sn interface and refine microstructure in the bulk solder region. Micro-cracks were detected at Cu/SAC interface and also in the Cu6Sn5 layer. This is due to the development of extremely (brittle) intermetallic layer and ductile nature of Sn–3.0Ag–0.5Cu solder. The intermetallic layer thickness increased substantially with the increase of reflow temperatures (230°C–290°C). A uniform distribution of SiC, Ag3Sn, and Cu6Sn5 IMCs were found in the bulk b-Sn matrix. The result shows that the SiC particles promote the extra nucleation sites for the development of b-Sn phase and IMCs in the solidified structure. In addition to this, SiC particles, b-Sn dendrites and IMCs can prevent dislocation slippage which helps in attaining a strong solder joint due to strong strengthening effect. The results showed that the spread ratio, spread factor, and the relative spread area (RSA) increased while the equilibrium contact angle decreased with an increase inreflowtemperature. This can be attributed to the strong adsorption effect and high surface free energy of the SiC particles.

The Sn-3.0Ag-0.5Cu (SAC305) composite solder reinforced micro-sized silicon carbide and nickel-coated silicon carbide (Ni-SiC) particles were produced by a high-energy ball milling process. SiC and Ni-SiC were homogeneously mixed into SAC305 lead-free solder alloy with distinctive (0.5, 1.0, and 1.5 wt.%) percent weight, through a powder metallurgy path. The growth of nickel on ceramic SiC (1-3 μm) particles was investigated by the electroless nickel (EN) method. The relative contact perimeter (RCP) and the wettability of SAC305 composite solder were investigated with the an image analysis software. The data from image analysis software shows that the relative contact perimeter, as well as the wettability of lead-free composite solders, were significantly improved.

Nowdays, the different material characterisation and testing methods are constantly evolving. With modern techniques, we have the ability to take a look inside the product without sample cutting, with modern CT systems. The modern techniques with their development become closer and closer to industrial applications. However, the testing protocols are sometimes 1 or 2 steps behind. This is mostly due to the cost or the complexness of the new testing methods. In this study we would like to take a quick look on the current standard industrial testing of porosities and microcracks and compare them with computer tomograph assisted testing.

Semi-continuously cast AlSi12 alloy was investigated by our research group at the University of Miskolc in the Institute of Physical Metallurgy, Metalforming and Nanotechnology under laboratory condition. Our goal was to define correlation and tendency between casting parameters and solidified microstructures. The examined alloy is used as filler material, thus cover soldering technology and exchangers are made from it, like car coolers, radiators, air conditioners. During the investigation optical microscope was used for sight of ingot microstructure, secondary dendrite arm spacing was measured in this way and even the amount of primary α-phase.

The target of our experiments is to simulate a complex production process under laboratory conditions. An industrial aluminium production line is examined using a semi-continuous casting device, running preliminary and trial experiments to find the optimal technological parameters for the physical simulation. Be the determination of the correct casting parameters the technological industrial process can be optimized.

In the general practice of ED-XRF measurements, the values of elemental concentrations are derived from complicated calculation methods. Hereby a simple mathematical formula is suggested, which provides an easy way to prepare standard samples. On the other hand, the simulation of spectral lines may also be a helpful tool for the calibration process. In this study, measured and simulated data were used for the quantitative analysis of ternary Au-Ag-Cu alloys. To determine the calibration points, the peak intensity ratio method was applied and the calibration curves were fitted. This work presents the results of a twofold investigation aimed at: a) finding a suitable computational tool to optimise the parameters of the underlying equations and b) testing the reliability of the simulated data to determine the concentrations of multi-element standard samples. Based on comparisons of calculated concentrations it can be stated that a simple calculation method with simulated data provides an easy tool to define calibration standards. It is also demonstrated that the parameters of the linear plots can be optimised to yield improved results.

In this study the effects of small amounts of nickel addition (0-2000 ppm) on the microstructure, on Cu6Sn5 intermetallic compound formation and the mechanical properties of a Sn-0.5Cu lead-free solder were investigated. It is known that even ppm level additions of Ni have significant effects on the microstructure of Sn-Cu solder alloys. Ni suppresses the growth of β-Sn dendrites in favour of eutectic formation. As the nickel content increases, the microstructure undergoes a morphology evolution from hypoeutectic through fully eutectic to hypereutectic. Furthermore, the presence of Ni in the Cu6Sn5 intermetallic compound phase stabilises its high-temperature allotrope η-Cu6Sn5.

Melting and crystallization processes of lead-free and lead-contaminated alloys in near-equilibrium state were investigated. In addition, the effect of silver content up to 4 wt.% on the microstructure of Sn-Ag-Cu alloys was studied. The volume fraction of β-Sn decreased by half owing to 4 wt.% Ag content. Furthermore, contamination by lead strongly influences the properties of the solidified microstructure. The Pb grains appear as a result of two processes when the Pb content is equal to 0.5 wt.% or higher: Pb phase solidifies in the quaternary eutectic at 176°C, and Pb grains precipitate from the primary β-Sn solid solution grain during a solid state reaction. The freezing range enlarges to 51°C due to 2 wt.% Pb content owing to quaternary eutectic. Above 1 wt.% Pb content, the mechanical properties also improve due to grains of quaternary eutectic Pb and precipitated Pb grains with a size

This paper investigates the effects of small amount nickel addition (0, 200, 400, 800, 1800 ppm) on the microstructure and the mechanical properties of Sn-0.7Cu lead-free solder alloys. It is known that even ppm level Ni additions have significant effects on the microstructure of Sn-Cu solder alloys. Ni suppresses the growth ofβ-Sn dendrites in favour of eutectic formation. As the nickel content increases, the microstructure undergoes a morphological evolution from hypoeutectic through fully eutectic to hypereutectic. Along with these transformations, the mechanical properties of the alloy also significantly change. Based on the experimental results presented in this paper, the Sn-0.7Cu solder achieves maximum strength at the addition level of 800 ppm Ni, when the microstructure becomes fully eutectic.

The present work reports the effect of substrate composition, thickness of the tin electroplate and its morphology on pressure-induced tin whisker formation. Pure tin deposits of different thickness were obtained on a copper and brass substrates using methane sulfonic industrial bath. The deposits were compressed by a steel bearing ball forming imprint on the surface. The microstructure of tin whiskers obtained at the boundary of each imprint, their length and number were studied using both light and scanning electron microscopy. It was shown that the most intensive formation and growth of whiskers was observed in the first two hours. In general, brass substrate was shown to be more prone to whisker formation than copper independently of the tin coating thickness. The results have been compared with industrial bright tin finish on control unit socket leads and proposals have been made as to modification of the production process in order to minimize the risk of whiskering.

In lead-free reflow soldering, the presence of voids should be taken into account. For this reason, the effect of the applied heating profiles was examined via the characterization of voids in galvanic and immersion Sn coatings. According to EU Directive 2002/95/EC, the screening of Pb element of reflow soldering (i.e. of electrical and electronic equipment) is necessary; and the practical implementation of this measurement is largely affected by the characteristics of the solder (i.e. the presence of voids and the inhomogeneity of the solder). Comparing the results of the above two coating methods, it was found that by chemical coating more voids were formed and the detected lead content was higher than for galvanic Sn. The standard deviation of Ag and Cu concentrations was mainly influenced by the appearance of large compounds in the second case, while with chemical coating, no large compounds were formed due to the elevated number of voids.

Interfacial intermetallic compounds (IMC) play an important role in Sn-Cu lead-free soldering. The size and morphology of the intermetallic compounds formed between the lead-free solder and the Cu substrate have a significant effect on the mechanical strength of the solder joint. In the soldering process of Sn-Cu alloys, Cu6Sn5 intermetallic compounds are formed. The complex structural behaviour of Cu6Sn5 IMC is temperature- and composition-dependent and it is long since subject to scientific research. The Cu6Sn5 phase basically exists in two crystal structures: hexagonal η-Cu6Sn5 (at temperatures above 186°C) and monoclinic η’-Cu6Sn5 (at lower temperatures). In the presence of Ni in the solder, the η-η’ transformation does not occur, therefore, the η-Cu6Sn5 phase remains stable. In this study the role of Ni in the (Cu,Ni)6Sn5 intermetallic compound in Sn-Cu lead-free solders was examined. Sn-Cu alloys with different Cu content (0.5 to 1 mass%) were modified through Ni addition. The morphology of the intermetallic compounds of the modified Sn-Cu alloys was investigated by optical microscopy (OM) and scanning electron microscopy (SEM), the IMC phases were examined with X-ray diffraction method (XRD).

Industry should gradually replace the tin-lead solder alloys used traditionally in the soft soldering technology by lead-free soldering alloys, which raises a lot of new technological and scientific problems to be solved. The introduction and application of lead-free alloys caused a number of soldering defects not observed earlier; mechanisms of their formation are still unclear. One of such defects is whisker formation, another one is intensified formation of intermetallic phases. The appearance of undesired intermetallic phases in the soldering material spoils its mechanical properties; therefore it is particularly important that these phases do not form in electronic components. Besides, the formation of intermetallic compounds may occur in the soldering bath, thus making the soldering process difficult or even impossible.Tin-copper-nickel and tin-silver-copper alloys are suitable for the replacement of tin-lead alloys. The components of these alloys were studied. After metallographic examination of the specimens the occurrence of intermetallic phases was determined by the XRD method. The identification of intermetallic phases was carried out by using literature data and phase diagrams.

Whiskers formed on the lead-free tin surfaces pose a serious risk to small electronic devices causing a short circuit and leading to the component/device failure. The present research was focused on the investigation of tin whisker formation on a motor control unit sockets made of tin coated copper, applying to the specimen mechanical load alone or together with heat treatment/electric current. Scanning Electron Microscopic (SEM) imaging was applied in order to study the microstructure of tin whiskers obtained, their length and number at the boundary of each imprint. If the mechanical stress increases from 1000 to 5000 MPa, the average number of whiskers and possible formation spots also increase from 570 to 1300. The length of whiskers varied from 3 μm after 0.5 h to 5.5 μm after 3 hours of exposition. It has been found that heat treatment at 150°C for 1 hour significantly reduces the number of whiskers (on average 6 times as few) formed. Therefore, the threat of failure of the electronic equipment is reduced.

High performance metal matrix syntactic foams (MMSFs) have been produced by liquid state infiltration of AlSi12 alloy into two loosely packed sets of different nominal diameter (150 μm and 1500 μm) oxide hollow spheres (CHSs) and their mixed packs. The structure of the MMSFs has been studied by X-ray computer tomography and microscopy. The mechanical properties were mapped by compressive tests. The structural investigations showed proper infiltration. In the case of pure small and large CHS filler, the compressive tests revealed high strength levels all over the deformation of the materials up to 50% compressive strain, with the dominance (higher strength values) of the smaller CHSs filled MMSFs. In the case of bimodal CHS filling, the compressive features of the MMSFs have been mixed with two local peaks corresponding to the failure of the smaller and larger CHS filled MMSFs. Rule of mixtures is applicable to estimate the compressive strength.

A lot of phases can be present in the structure of cast iron depending on the quality and the heat treatment processes. By using the color etching, the different phases – e.g. the carbides – can exactly be identified and their quantity can be measured. The carbide of iron (cementite) or other types of carbides existing in the structure have a significant influence on the properties of cast product therefore strict prescriptions regulate their quantity mainly in case of making cast products for the motor-car industry. In the course of our experiments performed by using the color etching, we proved that carbides can be detected and their quantity can be determined by using the digital image processing method by means of the different reagents. Other different characteristics of the structure can become visible by means of the reagents used during the color etching. During the investigations, it was experienced that some of the ferrite grains are etched in different color. This is probably connected to the orientation of grains as the thickness of interference-film is different on the anode phases having different orientation and therefore they color in different tones.

In the research work the precipitation hardening and/or equal channel angular pressing (ECAP) of PM aluminium alloy (AlCuSiMg) samples were investigated. The aim of the research was to determine the optimal parameters for precipitation hardening, especially temperature and time (in terms of maximal strength), and to test the ECAP pressing number for the same properties of precipitation hardened samples. The samples produced were studied by SEM, X-ray diffraction. The results showed that the PM samples had higher mechanical properties after one pressing by ECAP than after precipitation hardening with optimal parameters. In severe plastic deformation a heated die with a channel angle of 90° and ‘A’ route was used. During the heat treatment the applied temperature of the solution treatment was 420-540°C for 1 hour or 3 hours, and hardening was applied at 180°C for 5 hours.

The European Union and Japan initiated the issue of RoHS, the directive about the restriction of hazardous substances, which prohibits certain hazardous substances in electronic equipment - including lead - application. Due to the directive the use of lead free solder alloys is spreaded, however the Pb in the form of contamination may be appear under technological process. The lead impurity has significant effect on microstrucutre and lifetime so it is necessary to carry out detailed examinations. In this paper the study of intermetallic compounds in six-element, Pb impured, thermal cycles test-subjected, Sn-Ag-Cu (SAC) solder alloy is demonstrated

Composites are special material which can provide individual properties such as high strength with low density or good thermal conductivity with low thermal expansion coefficient. Composites conform to the constantly evolving and more complex expectations. In order to make a product with good quality, it is important to choose suitable materials and technology. In this research powder metallurgy (PM), as one of the most common composite manufacturing technology, was examined -which factors and mechanisms influence mostly the properties of the product. Ishikawa method was used to reveal these correlations.

This paper reports the results of ED-XRF method for the determination of low-level contaminated solders. The method was calibrated for the analysis of part-per-million (ppm) levels of Pb and major levels of other elements. In this work, two types of Sn-Ag based solder alloys are used; the ternary Sn-3.0wt%Ag-0.5wt%Cu (SAC305) and the 6-part Sn-3.5wt%Ag-3.2wt%Bi-1.6wt%Sb-0.5wt%Cu-0.15wt%Ni were examined. Empirical calibration and fundamental parameter calibration were used to analyze samples. The results of this study demonstrate the differences between the applied calibration methods for detection of Pb. Screening analysis of bulk samples from variant production lines were also discussed.

Al/SiC composites are used especially in automotive and aerospace industry due to the numerous advantageous mechanical properties. These end-products can be produced by casting or powder metallurgical techniques. High strength with high toughness can be reached only by perfect interfacial bonds between the matrix and reinforcing phase. To improve the interfacial bond, one of the methods is the surface coating of the SiC particles. But the metal layer of the reinforcing phase reacts with the matrix due to the high sintering temperature and long sintering time. In our research work the formation of Al-Ni intermetallic phase was investigated by Scanning electron microscopy (SEM) and X-ray diffraction measurements (XRD).

Automotive castings have to meet more and more versatile requirements these days. One of the most important requirements towards suppliers and foundries is producing parts of better quality, higher performance but at the same time of less weight. In order to couple this small weight with high performance and excellent quality these products should meet very strict mechanical standards of automotive parts. There is a constant need for production engineering developments ranging from purity degree - that is producing molten metal with high cleanness - to grain refinement and alloy improving including heat treatment technologies.

Hard turning process is widely used for finishing the hardened surfaces of machine parts exposed to high load. Such parts can be gears, bearings, or short shafts. As in each machining process, hard turning may change the properties of the surface layer. In this research work, we deal with material structure changes developing in the bore of gears made of a material of 20MnCr5. Microscope images show that the structure of the material is altered on the surface of the bores due to the turning process under different conditions. In certain cases, a certain layer that cannot be etched develops, called a white layer. Surface layer modification may take place using different technological data. In this paper, we will prove that proper selection of these technological data (cutting speed, depth of cut, feed rate) may eliminate the formation of a white layer or may decrease its thickness. The fine structure of this surface layer was investigated using the X-ray diffraction method, whilst the thickness of the layer was measured by a computer image analysis method. In this paper, the different conditions for the development of the white layer are described, its composition and some of its properties are determined, and the relationship between technological data and the thickness of the white layer is investigated.

Formability characterises the behaviour of the metals during shaping, more precisely, the accumulated deformation until rupture or fracture. Formability can be influenced by several factors and can be characterized with several methods. In this paper, the effect of the processes occurring during the pre-heating and homogenization of formable aluminium alloys was studied. Three commercial aluminum alloys, namely, 3003, 5005 and 5052 were involved into the investigation to reveal the different behaviours resulting from composition differences. The characterization of hot formability must be characterized by a rapid and simple method in cases when large number of sample series must be handled. In parallel, reliable results of the examination method is required. To fulfil both requirements, cold and hot compression tests were carried out with an Instron 5982 universal material tester equipment. The rapid heating of the samples during hot compression tests was realized with a unique own-made inductive heating device. Thus, the effect of dynamic recrystallization during hot compression, while static recrystallization during cold compression tests and subsequent annealing could be studied. The performed experiments were used to simulate the effects of the cold-rolling and hot-rolling. The resulting grain structures were studied with Barker etching technique.

One of the methods of melt-treatment of Al-Si alloys is the modification that plays a very significant role in the development of (mechanical) properties of finished product. There are a lot of well-known processes for the investigation of effectiveness of modification but an objective, exact result cannot be obtained in each case by using these methods. The method suitable for the classifi-cation of modification worked out by us was developed by integrating two methods namely the comparison by means of etalon-images and the integration of measurement of morphological pa-rameters. This method is relatively simple, does not demand lots of measurements and gives reliable results.

The A356 alloy, which consists of 100-200 ppm modifier, namely strontium was examined. The samples were solidified unidirectionally, and each sample had a pair which was solidified in a rotating magnetic field. The microstructure of the samples: morphology and the fraction of eutectic silicon was studied. The morphology of eutectic Si was very different in the samples - the samples solidified at different movement velocities – so it was necessary to determine the quantity of strontium. Magnetic stirring changes both the strontium content and the extent of modification. This paper describes the investigation methods and the effects of strontium modification.

The purpose of this study is to find a relationship between the parameters describing the microstructural homogeneity of SiC particle reinforced Al metal matrix composites. The Al-SiC powder mixtures having different particle size combinations were hot-pressed after careful mixing. The optical microscope images of the microstructures were processed by using an image analyzing program; the binary morphology was chosen for characterizing the SiC particle distribution.

The remote sensing techniques provide a great possibility to analyze the environmental processes inlocal or global scale. Landsat images with their 30 m resolution are suitable among others for landcover mapping and change monitoring. In this study three spectral indices (NDVI, NDWI, MNDWI) wereinvestigated from the aspect of land cover types: water body (W); plough land (PL); forest (F); vineyard(V); grassland (GL) and built-up areas (BU) using Landsat-7 ETM+ data. The range, the dissimilaritiesand the correlation of spectral indices were examined. In BU – GL – F categories similar NDVI valueswere calculated, but the other land cover types differed significantly. The water related indices (NDWI,MNDWI) were more effective (especially the MNDWI) to enhance water features, but the values of othercategories ranged from narrower interval. Weak correlation were found among the indices due to thedifferences caused by the water land cover class. Statistically, most land cover types differed from eachother, but in several cases similarities can be found when delineating vegetation with various watercontent. MNDWI was found as the most effective in highlighting water bodies.

Color etching is a widely used technique for visualizing different phases in metallic materials. Its advantage to the traditional etching techniques is that it gives additional information within one phase, namely, the color shade of a given phase can change in a certain range. This paper demonstrates that, due to the physics of the color etching, the shade of a phase also depends on the crystallographic orientation of the investigated grain. As a test material, spheroidal graphite cast iron was used, and individual grain orientation was identified by automated electron back scattering diffraction (EBSD). Results showed that there is a strong correlation between grain orientation and the shades obtained by color etching.

Composites containing powdered zinc, and zinc/lead acetate were prepared via frontal polymerization. In the case of the acetates, elemental metal was formed in an in situ decomposition process. The local area function was used to demonstrate the distribution of fillers, and the uniformity of the area fraction for the quantitative characterization of the distribution. With the use of metal acetates, composites of uniform metal distribution can be produced, unlike in systems with metal powder, where the metal particles are enriched at the margin of the sample. It can be established that the specific direct-current resistance significantly decreases in AA-TGDMA composites by the addition of zinc acetate, compared to that of the initial monomer mixture. On heating, the unreacted zinc acetate decomposes further, which results in the further decrease in electrical resistance.

The type, volume fraction, size, shape and arrangement of embedded particles influence the mechanical properties of the particle reinforced metal matrix composites. This presents the investigation of the SiC particle and porosity distributions in various aluminum matrix composites produced by cold- and hot-pressing. The microstructures were characterized by optical microscopy and stereological parameters. SiC and porosity volume fractions, and the anisotropy distribution function were measured to establish the influence of the consolidation method. The results showed that SiC particles are arranged in a different way during the cold- and hot pressing. The amount of porosity in the hot pressed specimens is always lower than that in the cold pressed ones; however, cold pressed and sintered samples have few large pores whereas more fine pores develop in the hot pressed ones. In the cold pressed specimens, heating rate for sintering influences the final density, the amount of porosity increases parallel to the increase in the relative particle size; and coating of SiC particles with Cu lowers the porosity while Ni-coating does not result in such an effect.