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    Effect of growth velocity on microstructure and mechanical properties of directionally solidified 7075 alloy
    (Taylor & Francis Ltd, 2020) Cadirli, Emin; Nergiz, Emel; Kaya, Hasan; Buyuk, Ugur; Sahin, Mevlut; Gunduz, Mehmet
    7075 alloys were prepared using metals of 99.99% high purity in the vacuum atmosphere. These alloys were directionally solidified upwards under various growth velocities (8.3-166.0 mu m/s) using a Bridgman-type directional solidification furnace. Dendritic spacings (lambda(1), lambda(2)) and microhardness (HV) were measured from both longitudinal and transverse sections of the samples. Ultimate tensile strength (sigma(U)) and yield strength (sigma(y)) of the solidified samples at room temperature were examined. The HV increased from 75.2 to 112.8 MPa, the sigma(U) increased from 155.8 to 210.1 MPa, and the sigma(y) increased from 198.4 to 319.8 MPa with increasing growth velocity from 8.3 to 166.0 mu m/s. Exponent values of the V for the lambda(1), lambda(2), HV, sigma(U) and sigma(y) were calculated as 0.27, 0.41, 0.05, 0.11 and 0.15, respectively. The results show that the hot tearing in the 7075 alloy is caused by the fracture of dendrites structures.
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    Effect of Heat Treatment on the Microstructures and Mechanical Properties of Al-4Cu-1.5Mg Alloy
    (Springer Int Publ Ag, 2022) Cadirli, Emin; Kaya, Hasan; Buyuk, Ugur; Ustun, Erkan; Gunduz, Mehmet
    In this work, the influence of different heat treatments (HT) processes on the microstructure and mechanical properties of cast Al-4Mg-1.5 Mg alloy was investigated. To investigate the effect of HT, firstly Al-4Cu-1.5Mg samples were homogenized (solution treatment) at 500 degrees C/2h, water quenched at room temperature (RT) and then immediately exposed to an artificial aging process at 200 degrees C for various aging times of 1, 4, 8, 12, 16, 20 and 24 hours. Quantitative examinations after HT processes (solution treatment and aging) have shown that intermetallic phases (Al2Cu and Al2CuMg) were dissolved in the alpha-Al matrix phase and distributed along the grain boundary. Some mechanical properties (HV sigma, sigma(TYS), sigma(UTS), sigma(CYS), E and delta) of a sufficient number of alloy samples exposed to different heat treatments were examined in detail. The data obtained show that the conditions of solution treatment and aging in some conditions show superior mechanical properties than the sample in the form as-cast. The highest microhardness value (126 HV) was obtained for the alpha-Al matrix phase, which was subjected to solution treatment (only homogenization). After aging for 1h at 200 degrees C, the peak value of microhardness was achieved as 289.5 HV for intermetallic phases. The highest tensile strength (sigma(UTS)) was obtained as 328 MPa for the sample which aged for 8h at 200 degrees C after solution treatment for 2h at 500 degrees C.
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    EFFECT OF HEAT TREATMENT ON THE MICROSTRUCTURES AND MECHANICAL PROPERTIES OF AL-4CU-1.5MG ALLOY (vol 16, pg 1020, 2021)
    (Springer Int Publ Ag, 2024) Cadirli, Emin; Kaya, Hasan; Buyuk, Ugur; Ustun, Erkan; Gunduz, Mehmet
    [Abstract Not Available]
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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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    The Effect of Growth Rate on the Microstructure and Mechanical Properties of 7020 Alloys
    (Springer, 2022) Kaya, Hasan; Buyuk, Ugur; Cadirli, Emin; Sahin, Mevlut; Gunduz, Mehmet
    The 7020 aluminum alloy is one of the hardenable Al-Zn-Mg based alloys, which are a family of high strength aluminum alloys. These 7020 alloys are commonly used in the aircraft and automotive industries. The microstructural changes have a significant impact on the mechanical properties of binary and multi-component alloys. For this reason, 7020 aluminum alloys were prepared with different growth rates on account of the changes in the microstructures; thus, directionally solidification processes were actualized with a Bridgman furnace at five various growth rates (V = 8.3-166.0 mu m/s) and at constant temperature gradient (G = 8.3 K/mm). Microhardness (HV), ultimate tensile strength (sigma(U)) and yield strength (sigma(y)) of the solidified alloys were determined. The HV increased from 758.8 to 917.1 N/mm(2), the sigma(U) from 125.4 to 208.1 N/mm(2) and the sigma(y) from 133.7 to 230.8 N/mm(2) with an increase in growth rate from 8.3 to 166.0 mu m/s.