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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 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...

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.

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).

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.

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.

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.