Electrochemical and wetting behavior of as-cast Sn-Zn-Sb lead free solders alloys

Ternary alloys SnZn12Sb8, SnZn10Sb10, SnZn8Sb12, SnZn6Sb14, and SnZn2Sb18 were prepared by induction melting. Electrochemical behavior and wetting (contact angle) of prepared as-cast samples were investigated using open circuit potential measurement and sessile drop technique. The results of electrochemical investigation show that open-circuit potential, few seconds after immersing of electrodes, shifts toward more negative values, indicating a relatively smaller rate of dissolution during the spontaneous dissolution process under the curentless conditions. After that period, the values of potential tend to be constant with time. It was found that all investigated alloys have poor wettability on copper substrate and the contact angle values decrease with increasing superheat temperature

Influence of activators on constitutes of diffusion layer at boronizing pressed samples from iron powder

In this paper, results of experimental investigation which contributes to study of quantitative changes of porosity during chemical-thermical process, apropos boronizing of pressed samples from iron powder, with variation of boronizing mixture composition are presented. The basic mixture is modified by the addition of activators with different chemical composition and in different percentage rate (0-4 wt%). Mixtures with ammonium chloride, ammonium bifluoride and boron potassium fluoride were investigated. According to the results of the experiments it is found that the content of activators has an influence on the porosity of pressed samples from iron powder. In order to obtain better boride layers it was necessary to choose a mixture for boronizing and to determine the most useful activators and their ratio. The results of research and mathematical processing enable the choice of optimal mixture composition for boroning.

Optimization of the aging regime of Al-based alloys

Successful simulation of problems and phenomena related to the changes of the alloys composition is possible by applying simplex plans. The concentration (simplex) triangle application for the design of the optimal regime of Al-5wt%Cu-Pb-Bi alloy aging process is presented in this paper. The iso-lines of the given alloy’s mechanical properties in temperature-aging time coordinates were obtained by applying the mathematical models based of the given aging regimes, and the obtained results of changed properties. Regression polynomial of the fourth degree was used as the mathematical model, whereas the effect of the aging regime has been observed through the changes of tensile strength and contraction. Based on the obtained results, we have come to the conclusion that the simplex lattice method can be successfully applied to a great number of heat treatment aspects when with the increase of the temperature the duration time must be reduced, and vice versa (aging, annealing, homogenizing, etc.)

The possibility of the boronizing process on the pressed samples of iron powder

The paper presents results of the experimental investigation of the boronizing process on nonsintering iron powder samples (NC100.24, Höganäs, Sweden). Experiments are planned within the limits of applicability of simultaneous sintering at chemical-thermal treatment process (boronizing). The simlex plan of 15 experimental points was used for the experiment, while a polynomial function of fourth degree was employed in the modeling of a mixture composition based on the volume changes, porosity and the depth layer changes. Boronizing was carried out in mixture with born carbide by addition of ammonium bifluoride, ammonium chloride and boron potassium fluoride as activators, by proportion definited plan

The influence of the temperature of solution heat treatment on the properties of 6000 series aluminium alloys

The 6000 series alloys belong to the group of aluminium alloys that contain magnesium and silicon as their two main alloying elements. In addition to these two alloying elements, the alloys contain manganese and other elements, in accordance to the type of alloy. Alloys from this series belong to the group of aluminium alloys which are susceptible to thermo-mechanical treatment. These alloys exhibit the best mechanical and physical properties when they are artificially aged, with the occurrence of the strengthening β'' phase. The process of ageing includes solution heat treatment, quenching and ageing at predefined temperatures for a specified amount of time. All the aforementioned processes have a direct impact on the physical and mechanical properties of the alloy following the performed thermal treatment. In this paper the influence of the temperature of solution heat treatment on the properties of two aluminium alloys belonging to the 6000 series was examined, EN AW-6060 and EN AW-6082. The samples were examined at five different temperatures varying from 510-590°C. In order to examine the influence of the temperature of solution heat treatment, measurements of the hardness and electrical conductivity of the samples were performed, following adequate thermal treatment. After the testing, analysis of the results showed that with the increase of the temperature of soluble annealing, there occurred an increase in hardness, and a decrease in electrical conductivity in the aged samples, due to a better homogenization which caused a better distribution of metastable phases

The microstructure and properties of as-cast Sn-Zn-Bi solder alloys

U radu su prikazani rezultati ispitivanja strukturnih i mehaničkih karakteristika bezolovnih lemnih legura u sistemu kalaj-cink-bizmut. Nakon dobijanja legura u indukcionoj peći sa zaštitnom atmosferom, trostrukim pretapanjem odmerene količine čistih metala, izvršena su ispitivanja strukture tako dobijenih uzoraka legura optičkom i skenirajućom electronskom mikroskopijom (SEM). Energetskom disperzivnom spektroskopijom (EDS) određen je hemijski sastav faza prisutnih u strukturi legura. Izvršena su merenja tvrdoće, i zatezne čvrstoće ispitivanih legura. Sva istraživanja su sprovedena sa ciljem boljeg upoznavanja osobina legura u sistemu Sn-Zn-Bi, koji se smatra odgovarajućom zamenom olovnih lemnih legura.Research on the lead-free solders has attracted wide attention, mostly as the result of the implementation of the Directive on the Restriction of the Use of Hazardous Substances in Electrical and Electronic Equipment. The Sn-Zn solder alloys have been considered to be one of the most attractive lead-free solders due to its ability to easily replace Sn-Pb eutectic alloy without increasing the soldering temperature. Furthermore, the mechanical properties are comparable or even superior to those of Sn-Pb solder. However, other problems still persist. The solution to overcoming these drawbacks is to add a small amount of alloying elements (Bi, Ag, Cr, Cu and Sb) to the Sn-Zn alloys. Microstructure, tensile strength, and hardness of the selected Sn-Zn-Bi ternary alloys have been investigated in this study. The SEM-EDS was used for the identification of co-existing phases in the samples. The specimens' microstructures are composed of three phases: Sn-rich solid solution as the matrix, Bi-phase and Zn-rich phase. The Bi precipitates are formed around the Sn-dendrit grains as well as around the Zn-rich phase. The amount of Bi segregation increases with the increase of Bi content. The Sn-Zn-Bi alloys exhibit the high tensile strength and hardness, but the values of these mechanical properties decrease with the increase of Bi content, as well as the reduction of Zn content. The results presented in this paper may offer further knowledge of the effects various parameters have on the properties of lead-free Sn-Zn-Bi solders

The microstructure and properties of as-cast Sn-Zn-Bi solder alloys

Research on the lead-free solders has attracted wide attention, mostly as the result of the implementation of the Directive on the Restriction of the Use of Hazardous Substances in Electrical and Electronic Equipment. The Sn-Zn solder alloys have been considered to be one of the most attractive lead-free solders due to its ability to easily replace Sn-Pb eutectic alloy without increasing the soldering temperature. Furthermore, the mechanical properties are comparable or even superior to those of Sn-Pb solder. However, other problems still persist. The solution to overcoming these drawbacks is to add a small amount of alloying elements (Bi, Ag, Cr, Cu, and Sb) to the Sn-Zn alloys. Microstructure, tensile strength, and hardness of the selected Sn-Zn-Bi ternary alloys have been investigated in this study. The SEM-EDS was used for the identification of co-existing phases in the samples. The specimens’ microstructures are composed of three phases: Sn-rich solid solution as the matrix, Bi-phase and Zn-rich phase. The Bi precipitates are formed around the Sn-dendrit grains as well as around the Zn-rich phase. The amount of Bi segregation increases with the increase of Bi content. The Sn-Zn-Bi alloys exhibit the high tensile strength and hardness, but the values of these mechanical properties decrease with the increase of Bi content, as well as the reduction of Zn content. The results presented in this paper may offer further knowledge of the effects various parameters have on the properties of lead-free Sn-Zn-Bi solders

Optimisation of the Recrystallisation Annealing Regime of Pd-5Ni Alloy Using experimental design and statistical analysis to understand the metallurgical properties of palladium alloy for ammonia oxidation catchment gauze applications

In this paper, changes in the mechanical properties of Pd-5Ni alloy are analysed after recrystallisation annealing in order to determine the optimal conditions for a thermomechanical processing regime for this alloy. The temperature and annealing time were varied and the resulting changes in hardness, tensile strength, relative elongation and proof strength were monitored. By using the simplex-lattice method and analysing experimental data, a fourth degree mathematical model-regression polynomial was defined and isolines of changes in the mechanical properties of the investigated alloys were designed depending on the conditions of heat treatment after rolling