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    Effect of silicon content on microstructure, mechanical and electrical properties of the directionally solidified Al-based quaternary alloys
    (Elsevier Science Sa, 2017) Cadirli, Emin; Buyuk, Ugur; Engin, Sevda; Kaya, Hasan
    Effect of silicon content on the microstructure (lamellar and flake), mechanical (microhardness, ultimate tensile strength) and electrical resistivity properties of Al-Cu-Fe-Si quaternary alloys has been investigated. Al-26Cu-0.5Fe-xSi (x = 6.5, 8, 10, 12 and 14 wt %) were prepared using metals of 99.99% high purity in the vacuum atmosphere. These alloys were directionally solidified under constant temperature gradient (8.50 Minim) and growth rate (8.25 mu m/s) by using a Bridgman type directional solidification furnace. Eutectic spacing, microhardness, ultimate tensile strength and electrical resistivity were expressed as functions of composition. The dependency of the eutectic spacing, microhardness, tensile strength and electrical resistivity on the composition (Si content) were determined. According to experimental results, the microhardness, ultimate tensile strength and electrical resistivity of the solidified samples increase with increasing the Si content, but decrease eutectic spacing. Variation of electrical resistivity with the temperature in the range of 300-650 K for studied alloys was also measured by using a standard d.c. four point probe technique. (C) 2016 Elsevier B.V. All rights reserved.
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    Microstructural, Mechanical, Electrical, and Thermal Properties of the Bi-Sn-Ag Ternary Eutectic Alloy
    (Wuhan Univ Technology, 2017) Kaya, Hasan; Engin, Sevda; Aker, Aynur; Buyuk, Ugur; Cadirli, Emin
    The development of lead-free solders has emerged as one of the key issues in the electronics packaging industries. Bi-Sn-Ag eutectic alloy has been considered as one of the lead-free solder materials that can replace the toxic Pb-Sn eutectic solder without increasing soldering temperature. We investigated the effects of temperature gradient and growth rate on the mechanical, electrical and thermal properties of the Bi-Sn-Ag ternary eutectic alloy. Bi-47 wt% Sn-0.68 wt% Ag alloy was directionally solidified upward with different temperature gradients ( G=2.33-5.66 K/mm) at a constant growth rate ( V=13.25 mu m/s) and with different growth rates ( V=6.55-132.83 mu m/s) at a constant temperature gradient ( G=2.33 K/mm) in the growth apparatus. The microstructures (lambda), microhardness ( HV), tensile stress ( sigma), electrical resistivity (rho), and thermal properties (Delta H, C-p, T-m) were measured on directionally solidified samples. The dependency of the lambda, HV, sigma, and rho on G and V was investigated. According to the experimental results, lambda values decrease with increasing G and V, but HV, lambda, and rho values increase with increasing G and V. Variations of electrical resistivity (rho) for cast samples with the temperature in the range of 300-400 K were also measured by using a standard dc four-point probe technique. The enthalpy of fusion (Delta H) and specific heat ( C-p) for the same alloy was also determined by means of differential scanning calorimeter ( DSC) from heating trace during the transformation from eutectic liquid to eutectic solid.
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    Unidirectional solidification of Zn-rich Zn-Cu hypoperitectic alloy
    (MATERIALS RESEARCH SOC, 2009) Kaya, Hasan; Engin, Sevda; Boyuk, Ugur; Cadirli, Emin; Marasli, Necmettin
    Zn-0.7 wt% Cu-hypoperitectic alloy was prepared in a graphite crucible under a vacuum atmosphere. Unidirectional solidification of the Zn-0.7 wt% Cu-hypoperitectic alloy was carried out by using a Bridgman-type directional solidification apparatus under two different conditions: (i) with different temperature gradients (G = 3.85-9.95 K/mm) at a constant growth rate (41.63 mu m/s) and (ii) with different growth rate ranges (G = 8.33-435.67 mu m/s) at a constant temperature gradient (3.85 K/mm). The microstructures of the directionally solidified Zn-0.7 wt% Cu-hypoperitectic samples were observed to be a cellular structure. From both transverse and longitudinal sections of the samples, cellular spacing (lambda) and cell-tip radius (R) were measured. The effects of solidification-processing parameters (G and V) on the microstructure parameters (lambda and R) were obtained by using a linear regression analysis. The present experimental results were also compared with the current theoretical and numerical models and similar previous experimental results.