Twinned dendrites in Al-Zn alloy with high Zn content (40% wt.%) were successfully prepared by directional solidification. At different directional solidification rates (1000 and 1500 μm/s), microstructures and growth orientation variations of Al twinned dendrite and non-twinned dendrite were characterized. By using the inverted trapezoidal graphite sleeve at 1000 μm/s, Al twinned dendrite were formed to developed feather crystal structures in longitudinal section. Its primary and secondary twinned dendrite were grew along [110] direction. Moreover the deviation angle between [110] direction of Al twinned dendrite and the heat flow direction was about 27.15°. While not using the inverted trapezoidal graphite sleeve at 1000 and 1500 μm/s, Al dendrite was the non-twinned dendrite and the twinned dendrite was not appeared. The experimental results showed that the higher temperature gradient, a certain pulling rate and convection environment were the formation conditions of twinned dendrites.
Dendritic cells (DCs) due to their ability to present antigens are essential during the immune response to infections. The aim of the study was to evaluate the influence of bovine leukaemia virus (BLV) infection on DC properties. Cytokine profiles of myeloid, plasmacytoid and mono- cyte derived DCs from BLV infected cattle were analysed. Concentrations of IL-6, IL-10, IL-12, IFN-γ, and TNF-α in DC cultures were measured by flow cytometry. Obtained results indicated activation of pDCs population, where a significant increase in production of the IFN-γ was shown. Meanwhile, a decrease in production of IFN-γ and increase in production of IL-10 were shown in mDCs; the main population responsible for antigens presentation. This may indicate a contribu- tory role of the population during the process of persistent infection. In MoDCs population a significant elevation in secretion of proinflammatory cytokines – IL-6 and TNF-α was noted.
A comprehensive understanding of melt quality is of paramount importance for the control and prediction of actual casting characteristics. Among many phenomenon that occur during the solidification of castings, there are four that control structure and consequently mechanical properties: chemical composition, liquid metal treatment, cooling rate and temperature gradient. The cooling rate and alloy composition are most important among them. This paper investigates the effect of the major alloying elements (silicon and copper) of AlSi-Cu alloys on the size of secondary dendrite arm spacing. It has been shown that both alloying elements have reasonable influence on the refinement of this solidification parameter
The quality of the squeeze castings is significantly affected by secondary dendrite arm spacing, which is influenced by squeeze cast input
parameters. The relationships of secondary dendrite arm spacing with the input parameters, namely time delay, pressure duration, squeeze
pressure, pouring and die temperatures are complex in nature. The present research work focuses on the development of input-output
relationships using fuzzy logic approach. In fuzzy logic approach, squeeze cast process variables are expressed as a function of input
parameters and secondary dendrite arm spacing is expressed as an output parameter. It is important to note that two fuzzy logic based
approaches have been developed for the said problem. The first approach deals with the manually constructed mamdani based fuzzy
system and the second approach deals with automatic evolution of the Takagi and Sugeno’s fuzzy system. It is important to note that the
performance of the developed models is tested for both linear and non-linear type membership functions. In addition the developed models
were compared with the ten test cases which are different from those of training data. The developed fuzzy systems eliminates the need of
a number of trials in selection of most influential squeeze cast process parameters. This will reduce time and cost of trial experimentations.
The results showed that, all the developed models can be effectively used for making prediction. Further, the present research work will
help foundrymen to select parameters in squeeze casting to obtain the desired quality casting without much of time and resource
consuming.
In this study, the effects of grain size refiner addition and various pre-heating mold temperatures on AlSi9 cast alloy microstructure and solidification have been evaluated. For different process conditions, thermal analysis was performed for all samples and cooling curves were established. Important parameters in liquidus and eutectic Si-phase regions have been calculated using the first derivative cooling curves. Secondary Dendrite Arm Spacing (SDAS) variation was also determined. Experimental results question the effectiveness of cooling curve parameters in providing the microstructure data as a function of refinement. The present work shows that the effect of grain refiner addition on the value of SDAS was higher when the solidification time was lower. It indicated that the solidification parameters such as nucleation temperatures of α-Al phase, undercooling temperature and total solidification time were affected by grain refinement. It has been found that the addition of grain refiner affect the eutectic phase formation time. However, it has no effect on the eutectic phase morphology.
What is the limit of improvement the structure obtained directly from the liquid state, with possible heat treatment (supersaturation and aging)? This question was posed by casting engineers who put arbitrary requirements on reducing the DAS (Dendrite Arm Spacing) length to less than a dozen microns. The results of tests related to modification of the surface microstructure of AlSi7Mg alloy casting treated by laser beam and the rapid remelting and solidification of the superficial casting zone, were presented in the paper. The local properties of the surface treated with a laser beam concerns only a thickness ranging from a fraction to a single mm. These local properties should be considered in the aspect of application on surfaces of non-machined castings. Then the excellent surface layer properties can be used. The tests were carried out on the surface of the casting, the surface layer obtained in contact with the metal mould, after the initial machining (several mm), was treated by the laser beam. It turned out that the refinement of the microstructure measured with the DAS value is not available in a different way, i.e. directly by casting. The experimental-simulation validation using the Calcosoft CAFE (Cellular Automaton Finite Element) code was applied.