The study includes the results of research conducted on selected lead-free binary solder alloys designed for operation at high temperatures.

The results of qualitative and quantitative metallographic examinations of SnZn alloys with various Zn content are presented. The

quantitative microstructure analysis was carried out using a combinatorial method based on phase quanta theory, per which any

microstructure can be treated as an array of elements disposed in the matrix material. Fatigue tests were also performed using the

capabilities of a modified version of the LCF method hereinafter referred to in short as MLCF, which is particularly useful in the

estimation of mechanical parameters when there are difficulties in obtaining many samples normally required for the LCF test. The fatigue

life of alloys was analyzed in the context of their microstructure. It has been shown that the mechanical properties are improved with the

Zn content increasing in the alloy. However, the best properties were obtained in the alloy with a chemical composition close to the

eutectic system, when the Zn-rich precipitates showed the most preferred morphological characteristics. At higher content of Zn, a strong

structural notch was formed in the alloy because of the formation in the microstructure of a large amount of the needle-like Zn-rich

precipitates deteriorating the mechanical characteristics. Thus, the results obtained during previous own studies, which in the field of

mechanical testing were based on static tensile test only, have been confirmed. It is interesting to note that during fatigue testing, both

significant strengthening and weakening of the examined material can be expected. The results of fatigue tests performed on SnZn alloys

have proved that in this case the material was softened.

The results of studies presented in this article are an example of the research activity of the authors related to lead-free alloys. The studies covered binary SnZn90 and SnZn95 lead-free alloys, including their microstructure and complex mechanical characteristics. The microstructure was examined by both light microscopy (LM) and scanning electron microscopy (SEM). The identification of alloy chemical composition in micro-areas was performed by SEM/EDS method. As regards light microscopy, the assessment was of both qualitative and quantitative character. The determination of the geometrical parameters of microstructure was based on an original combinatorial method using phase quantum theory. Comprehensive characterization of mechanical behavior with a focus on fatigue life of alloys was performed by means of the original modified low cycle fatigue method (MLCF) adapted to the actually available test machine. The article discusses the fatigue life of binary SnZn90 and SnZn95 alloys in terms of their microstructure. Additionally, the benefits resulting from the use of the combinatorial method in microstructure examinations and MLCF test in the quick estimation of several mechanical parameters have been underlined.

Lead-free alloys containing various amounts of zinc (4.5%, 9%, 13%) and constant copper addition (1%) were discussed. The results of

microstructure examinations carried out by light microscopy (qualitative and quantitative) and by SEM were presented. In the light

microscopy, a combinatorial method was used for the quantitative evaluation of microstructure. In general, this method is based on the

phase quanta theory according to which every microstructure can be treated as an arrangement of phases/structural components in the

matrix material. Based on this method, selected geometrical parameters of the alloy microstructure were determined. SEM examinations

were based on chemical analyses carried out in microregions by EDS technique. The aim of the analyses was to identify the intermetallic

phases/compounds occurring in the examined alloys. In fatigue testing, a modified low cycle fatigue test method (MLCF) was used. Its

undeniable advantage is the fact that each time, using one sample only, several mechanical parameters can be estimated. As a result of

structure examinations, the effect of alloying elements on the formation of intermetallic phases and compounds identified in the examined

lead-free alloys was determined. In turn, the results of mechanical tests showed the effect of intermetallic phases identified in the

examined alloys on their fatigue life. Some concepts and advantages of the use of the combinatorial and MLCF methods in materials

research were also presented.

The article presents the study results of Sn-Zn lead-free solders with the various Zn content. The results concern the hypoeutectic, eutectic and hypereutectic alloys containing respectively 4.5% Zn, 9% Zn and 13.5% Zn. Moreover, these alloys contain the constant Ag (1%) addition. The aim of the study was to determine the microstructural conditionings of their fatigue life. In particular it was focused on answer the question what meaning can be assigned to the Ag addition in the chemical composition of binary Sn-Zn alloys. The research includes a qualitative and quantitative assessments of the alloy microstructures, that have been carried out in the field of light microscopy (LM). In order to determine some geometrical parameters of the microstructure of alloys the combinatorial method based on the phase quanta theory was applied. Moreover, for the identification necessities the chemical analyses in the micro-areas by SEM/EDS technics were also performed. Based on the SEM/EDS results the phases and intermetallic compounds existing in the examined lead-free solders were identified. The mechanical characteristics were determined by means of the modified low cycle test (MLCF). Based on this method and on the results obtained every time from only one sample the dozen of essential mechanical parameters were evaluated. The research results were the basis of analyzes concerning the effects of microstructural geometrical parameters of lead-free alloys studied on their fatigue life at ambient temperature.

In the work five ceramic compounds based on the (K0.44Na0.52Li0.04)NbO3 (KNLN) material modified with oxides: Cr2O3, ZnO, Sb2O3 or Fe2O3 (in an amount of 0.5 mol.%) were obtained. The KNLN-type composition powder was prepared by solid phase synthesis from a mixture of simple oxides and carbonates, while compacted of the ceramic samples was conducted by free sintering methods. In the work the effect of the used admixture on the electrophysical properties of the KNLN ceramics was presented. The XRD, EDS tests, the SEM measurements of the morphology ceramic samples, dielectric properties and DC electric conductivity were conducted. The research showed that the used admixtures introduced into the base of KNLN-type composition improve the microstructure of the ceramic samples and improve their sinterability. In the case of the dielectric measurements, it was observed a decrease in the maximum dielectric permittivity at the TC for dopred KNLN-type samples. The addition of an admixture of chromium, zinc, antimony or iron in an amount of 0.5 mol.% to the base composition (K0.44Na0.52Li0.04)NbO3 practically does not change the phase transition temperature. The diminution in the density value of doped KNLN ceramics was attributed to the alkali elements volatilization.

The paper presents the technology and basic properties of three compositions of lead-free ceramics: (i) (K0.44Na0.52Li0.04)NbO3, (ii) (K0.44Na0.52Li0.04)NbO3+0.5%mol Nd2O3 and (iii) (K0.44Na0.52Li0.04)NbO3+0.5%mol Pr2O3. Powders of the designed compositions based on KNLN were obtained with the classic ceramic technology, as a result of solid phase synthesis, from a mixture of simple oxides and carbonates. The synthesis of ceramic powders was carried out at Ts = 900°C for ts = 4 h, while compaction by free sintering at Tsint = 1100°C for tsint = 2 h.

XRD studies have shown that doping with praseodymium and neodymium promotes the formation of the tetragonal phase in the base composition (K0.44Na0.52Li0.04)NbO3 at lower temperatures. On the other hand, microstructural tests have shown that the admixture of neodymium and praseodymium improves the sinterability of ceramic samples during the technological process; however, the ceramic samples still exhibit high porosity.

In this study, lead-free 0.94 Na0.5Bi0.5TiO3-0.06BaTiO3 (NBT-BT) compositions at morphotropic phase boundary were successfully synthesized by solid-state reaction method. The effects of the particle size for various milling time (12-24-48 hours) and sintering temperatures (1100-1125-1150-1175oC for 2h) on the electrical properties of the NBT-BT ceramics were evaluated. Experimental results showed that particle size and sintering temperatures significantly affect the electrical properties of NBT-BT ceramics. The particle size of the ceramic powders decreasing while milling time increases to 48 hours. Particle size values for 0, 12, 24 and 48 hours (h) milled powders were measured as nearly 1.5 µm, 1 µm, 700 nm, and 500 nm respectively. The bulk density enhanced with increasing sintering temperature and showed the highest value (5.73 g/cm3) at 1150oC for 48h milled powder. Similarly, the maximum piezoelectric constant (d33) = 105 pC/N, electromechanical coupling coefficient (kp) = 25.5% and dielectric constant (KT) = 575 were measured at 1150oC for 48 h milled powder. However, mechanical quality factor (Qm) was reduced from 350 to 175 with decreasing particle size. Similarly, remnant polarization was dropped by decreasing powder particle size from 56 μC/cm2 to 45 μC/cm2.

The ecological factor is very important in shaping properties of alloys. It leads to a limitation or elimination, from the surroundings, of harmful elements from the heavy metals group. The so-called eco-brasses group comprises common lead-free brasses containing 10 to 40% of zinc and arsenic brasses of a high dezincification resistance. Among standardized alloys, CW511L alloy ( acc. to EN standard) or MS-60 alloy (acc. to DIN) can be mentioned. Investigations were performed on two different kinds of metal charges: ingots cast by gravity and the ones obtained in the semi-continuous casting technology with using crystallizers. The casting quality was analysed on the basis of the microstructure images and mechanical properties. The investigations also concerned increasing the corrosion resistance of lead-free alloys. This resistance was determined by the dezincification tendency of alloys after the introduction of alloying additions, i.e. aluminium, arsenic and tin. The investigations focused on the fact that not only alloying additions but also the production methods of charge materials are essential for the quality of produced castings. The introduced additions of aluminium and tin in amounts: 0÷1.2 wt% decreased the dezincification tendency, while arsenic, already in the amount of 0.033 wt%, significantly stopped corrosion, limiting the dezincification process of lead-free CuZn37 brass. At higher arsenic contents, corrosion occurs only within the thin surface layer of the casting (20 μ).