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    Characterization of rapidly solidified Ni-Si and Co-Al eutectic alloys in drop tube
    (ELSEVIER SCIENCE BV, 2010) Cadirli, E.; Herlach, D. M.; Volkmann, T.
    Containerless solidifications of Ni-Si and Co-Al eutectic alloys were carried out using an 8 m drop tube. Molten alloy ejected into a drop tube was rapidly cooled and solidified during free fall. The microstructures of the rapid solidified alloys were evaluated. It was seen that the microstructures of Ni-Si and Co-Al eutectics change from the lamellar and plate-like eutectic to the anomalous eutectic and needle-like forms with decreasing the sample size, respectively. The values of the enthalpy of fusion and specific heat were determined by means of differential scanning calorimetry (DSC) during the transformation from liquid to the solid state. The microhardness of rapid solidified alloys was measured by using a microhardness test device. According to the present measurements, the values of microhardness (HV) for rapid solidified Ni-Si and Co-Al eutectics alloys increase with decreasing the eutectic spacing. (C) 2009 Elsevier B.V. All rights reserved.
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    Microstructural, mechanical, electrical and thermal characterization of arc-melted Ni-Si and Co-Si alloys
    (ELSEVIER SCIENCE BV, 2010) Cadirli, E.; Herlach, D. M.; Davydov, E.
    This work presents the results of characterization of as solidified arc-melted Ni-Si and Co-Si alloys. The alloys of different compositions of the constitutions Ni, Co, and Si of purity of 99.99% were prepared by arc melting method under argon atmosphere in a water-cooled copper crucible with a non-consumable tungsten electrode and titanium getter. The effects of Si addition to pure Ni and Co on microstructure, microhardness (HV), electrical resistivity (p), latent heat of fusion (AN) and specific heat change (AC) were investigated. The measurements of microhardness of the samples were performed by using a microhardness test device. The dependence of microhardness on composition (C-o) was analyzed. According to these results, it has been found that with increasing the amount of Si the HV increases. Variations of electrical resistivity of the samples with the temperature in the range of 300-800 K were also measured by using a standard d.c. four-point probe technique. The Delta H and Delta C-p of the same alloys were determined by means of differential scanning calorimeter (DSC) from heating trace during the transformation from solid to liquid. (C) 2010 Elsevier B.V. All rights reserved.