Ümit Bayram

Dependence of microstructural, mechanical and electrical properties on growth rates in directional solidified Zn—Al—Bi eutectic alloy

Abstract Zn—5%Al—0.2%Bi (mass fraction) alloy was directionally solidified upward at a constant temperature gradient with a wide range of growth rates using a Bridgman-type directional solidification furnace. The eutectic spacings, microhardness, ultimate tensile strength and electrical resistivity for directionally solidified Zn—Al—Bi alloy were measured. Dependence of eutectic spacings, microhardness, ultimate tensile strength and electrical resistivity on growth rates was obtained by linear regression analysis. The results obtained in the present work for low growth rates (smaller than 450.0 μm/s) are in good agreement with experimental results obtained in previous work for directional solidified Zn—Al eutectic alloy with a similar growth rate but differs from the Jackson—Hunt eutectic theory and those obtained in previous experimental works at higher growth rates. The critical growth rate might be 450.0 μm/s for the Zn—Al—Bi eutectic alloy. From the plot of heat flow versus temperature, enthalpy of fusion, specific heat difference between liquid and solid phases and melting temperature for the Zn—Al—Bi alloy are found to be 112.55 J/g, 0.291 J/(g·K) and 660.20 K, respectively.

Dependence of microstructure, microhardness, tensile strength and electrical resistivity on growth rates for directionally solidified Zn-Al-Sb eutectic alloy

Abstract Zn-5.3 wt.% Al-0.8 wt.% Sb alloy was directionally solidified upward at a constant temperature gradient (G = 2.39 K mm−1) with a wide range of growth rates (V) (9.70 – 2 013.40 μm s−1) by using a Bridgman type directional solidification furnace. The average values of eutectic spacing (λ), microhardness (HVT), ultimate tensile strength (σUTS) and electrical resistivity (ρ) were measured from transverse sections of the directionally solidified samples. The dependency of λ, HVT, σUTS and ρ on V were experimentally obtained by using linear regression analysis for low, high and all growth rates. The bulk growth rates were also determined by using the measured values of λ and V for low, high and all growth rates. The results obtained in the present work were compared with the Jackson–Hunt eutectic theory and similar experimental results in the literature. Also, the specific heat difference (ΔCP) and enthalpy of fusion (ΔH) for the Zn–Al–Sb alloy were determined by means of differential scanning calorimetry.

Thermal Conductivity of Solid Phases for Naphtol, Camphene, Salol, and Bezil

Dependencies of thermal conductivity of solid phases on temperature have been investigated by using radial heat flow apparatus for naphthol, camphene, salol, and benzil. From graphs of the solid phase’s thermal conductivity variations versus temperature, the thermal conductivities of the solid phases for naphthol, camphene, salol, and benzil have been determined at their melting temperatures. The ratios of thermal conductivity of the liquid phase to thermal conductivity of the solid phase for naphthol, camphene, salol, and benzil have also been determined with a Bridgman-type directional solidification apparatus at their melting temperatures.