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Correlation of Hardness and Silicon Morphology for Al-Si-Sb Alloy

Uzun O., Yilmaz F., Emeksiz C., Ergen S., Kolemen U.

Archives of Metallurgy and Materials

2018

Vol. 63, iss. 1

467--472

In this study, we have focused on the role of silicon morphology on the hardness of eutectic Al–12 wt.% Si–0.5 wt.% Sb alloy solidified at different cooling rates. The alloys were produced by using induction melting, arc-remelting and melt-spinning techniques. The cooling rates of the alloys were determined as 0.5, 60 and ~105°C.s-1 for induction-melted, arc-remelted and meltspun alloy. The experimental results show that as the cooling rate increased the coarse silicon phase was substantially refined and its morphology altered from sharp need-like to round shape. Two exothermic peaks, attributed to precipitation and coarsening of silicon from supersaturated α-Al, were observed in the DSC curve of MS alloy. Vicker’s hardness of melt-spun alloy was found two times higher than those of IMed and ARed alloys. The lowest hardness of induction-melted alloy was ascribed to the lamellar morphology of silicon, yielding decohesive rupture. This result was confirmed by finite element analyzing.

AC susceptibility study of YBCO

Guclu N., Kolemen U.

Materials Science Poland

2011

Vol. 29, No. 3

209--215

The temperature dependence of ac susceptibility of YBCO bulk samples was measured as a function of ac field amplitude and frequency. Analysis of the temperature dependence of the ac susceptibility near the transition temperature (Tc) has been done employing the simplified Kim model. We have obtained an empirical function for the penetration field Hp = Ha(1-t)b ,t = T=Tc. Best fitting to data was obtained with parameters Ha 6:2103 A/m and b 1:50. The experimental value agrees well with the model calculations. In addition, as the frequency increases, the peak temperature (Tp) shifts to higher temperature. This effect can be interpreted in terms of flux creep. The field dependence of activation energy obtained from the Arrhenius plots for the frequency ( f ) and (Tp) can be described as U ž (Hac)-b0 with b0 0:38 for YBCO.