Investigation of the thermoelectrical properties of the Sn91.2-x–Zn8.8–Agx alloys

Sn91.2-x–Zn8.8–Agx alloys (x = 0.15–10.0 wt%) were directionally solidified upwards at a constant G (4.16 K mm-1) and V (41.5 µm s-1) in a Bridgman-type directional solidification furnace. The electrical resistivity (?) measurements of the alloys depending on the temperature were performed using the standard four-point probe method, and the temperature coefficients of the resistivities (?) were calculated. Composition analyses of the alloys were carried out using energy-dispersive X-ray spectroscopy. The enthalpy (?H) and the specific heat (?Cp) values of the alloys were determined by differential scanning calorimetry analysis. The thermal conductivity (K) values were obtained from the Wiedemann–Franz equation. According to the experimental results, electrical resistivities increased up to 3.0 mass% Ag and decreased with further increase in Ag content. Enthalpy and specific heat values decreased with the increasing content of Ag. The results were compared with the previous works for Sn–Zn–Ag alloys. © 2017, Akadémiai Kiadó, Budapest, Hungary.Ömer Halisdemir ÜniversitesiAcknowledgements This project was supported by the Nig^de Ömer Halisdemir University Scientific Research Project Unit under Contract No: FEB 2013/18. The authors would like to thank to Nig^de University Scientific Research Project Unit for their financial support

Effects of Growth Rates and Compositions on Dendrite Arm Spacings in Directionally Solidified Al-Zn Alloys

Dendritic spacing can affect microsegregation profiles and also the formation of secondary phases within interdendritic regions, which influences the mechanical properties of cast structures. To understand dendritic spacings, it is important to understand the effects of growth rate and composition on primary dendrite arm spacing (?1) and secondary dendrite arm spacing (?2). In this study, aluminum alloys with concentrations of (1, 3, and 5 wt pct) Zn were directionally solidified upwards using a Bridgman-type directional solidification apparatus under a constant temperature gradient (10.3 K/mm), resulting in a wide range of growth rates (8.3–165.0 µm/s). Microstructural parameters, ?1 and ?2 were measured and expressed as functions of growth rate and composition using a linear regression analysis method. The values of ?1 and ?2 decreased with increasing growth rates. However, the values of ?1 increased with increasing concentration of Zn in the Al-Zn alloy, but the values of ?2 decreased systematically with an increased Zn concentration. In addition, a transition from a cellular to a dendritic structure was observed at a relatively low growth rate (16.5 µm/s) in this study of binary alloys. The experimental results were compared with predictive theoretical models as well as experimental works for dendritic spacing. © 2017, The Minerals, Metals & Materials Society and ASM International.Firat University Scientific Research Projects Management UnitThis project was supported by the Erciyes University Scientific Research Project Unit under Contract No: FBD-12-3978. The authors are grateful for this financial support

Investigation of the thermo-electrical properties of A707 alloys

In the present work, the thermal conductivity, electrical conductivity, enthalpy of fusion, specific heat capacity and thermal diffusivity of the A707 alloy (Al–4.5 Zn–1.2 Mg–0.15 Cr–0.15 Zr wt.%) have been investigated. Phase identification of the studied alloy was investigated with energy dispersive X-ray analysis and X-ray diffraction techniques. Thermal conductivity of as-cast A707 alloy was measured using Comparison Cut Bar Method in the temperature range of 300–800 K. With the increase of temperature, thermal conductivity decreased gradually in as-cast A707 alloy. The electrical conductivities of the sample were obtained with the Wiedemann–Franz equation by using the measured thermal conductivity values. Thermal conductivity coefficients for the alloy were obtained from the graphs of thermal conductivity versus temperature. The enthalpy of fusion and the specific heat capacity during the transformation were also determined. Thermal diffusivity changes were calculated as a function of temperature through the obtained thermal data. © 2019 Elsevier B.V.Firat University Scientific Research Projects Management UnitThis project was supported by Erciyes University Scientific Research Project Unit under Contract No: FBA-2017-7241 . The authors thank Erciyes University Scientific Research Project Unit for their financial support