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    Effects of Deformation on Microstructure of Cu-Zn-Ni Alloy
    (Gazi Univ, 2012) Celik, Harun; Aldirmaz, Emine; Aksoy, Ilhan
    The thermal and mechanical effects on microstructure of Cu-12.44%Zn-4.75%Ni (wt%) alloy were investigated. The effects mechanical on both rapidly cooled sample and slowly cooled sample obtained from Cu-Zn-Ni alloy were investigated by using scanning electron microscopy (SEM), X-ray diffraction techniques (XRD). The thermal energy changes of in the alloy were examined by means of differential scanning calorimetry (DSC). As a result of SEM observations, annealing twins structures are observed in rapidly and slowly cooled samples. According to pictures of the SEM and XRD, the stress applied to samples caused to lose existing annealing twins, and led to formation of slip planes lying parallel to each other in between plates. The stress-strain behaviour is associated with applied heat treatment effect to samples. It's shown that the intensities of XRD peaks to be decrease, as a result of the increase in cooling rate. This result indicates that density defects of crystal increases with rapidly cooled in the Cu-Zn-Ni alloy. In both samples of the thermal energy changes, at the process of diffusion transformation eutectoid separation reactions have been proved to exist.
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    Öğe
    Micro-structural analysis of self-accommodating martensites in Cu-11.92 wt%Al-3.78 wt%Ni shape memory alloy
    (Elsevier Science Sa, 2008) Sari, Ugur; Aksoy, Ilhan
    Morphologies and configurations of the self-accommodating martensites in Cu-11.92 wt%Al-3.78wt%Ni shape memory alloy were studied by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). From microstructural observations, it is clearly observed that the self- accommodating martensites have typical plate group configuration. Each martensite plate group consists of four variants A, B, C, and D. Usually, variants A and C (or B and D) form characteristic spear morphology and variants A and D (or B and C) form fork morphology. Variants A and C are twin-related with respect to the ((1) over bar (2) over bar 1)(2H) mirror plane of the 2H martensite. Additionally, TEM observations reveal that two kinds of close-packed martensite structures, 2H (gamma(')(1)) and 18R (beta(')(1)) martensites, coexist in the quenched alloy. These structures occur by the localized formation of four variants of a plate group in a self-accommodating manner to minimize the total shape change. (c) 2007 Elsevier B.V. All rights reserved.