Showing 3 results for Samadi
A. Samadi, A. Abdollah-Zadeh, S.h. Razavi , H. Assadi,
Volume 29, Issue 1 (Jun 2010)
Abstract
The initial stages of the precipitation in a dilute Ni-Al binary alloy, Ni-11.6 at.%Al, were studied using differential
scanning calorimetry (DSC), X-ray diffraction (XRD), electron diffraction and electron microscopy (FEG-SEM and TEM) techniques. Three samples were similarly solution treated and then cooled to room temperature under different cooling rates, 170، 25 and 0.03oCs-1. The results indicate a clearly homogenous nucleation during rapid quenching which takes place via simultaneous ordering and phase separation. However, by decreasing the cooling rate to 25oCs-1 the nucleation mechanism changes to heterogeneous on the preferred nucleation sites. The capability of the mentioned empirical techniques for studying the initial stages of the γ′ is another subject which is studied in this article.
M. Khalili Savadkoohi, A. Samadi,
Volume 31, Issue 2 (Dec 2012)
Abstract
Coherency elastic strain between γ and is one of the effective factors which affect the morphology, spatial re-arrangement and coarsening kinetics of precipitates in nickel-base superalloys. In this investigation, using X-ray diffraction (XRD) technique, the - constrained and unconstrained lattice misfits were calculated for different morphologies of the precipitates in Inconel 738LC nickel-base superalloy. The constrained and unconstrained misfits, hence the coherency elastic strains of different morphologies of the precipitates were calculated from the XRD patterns of the bulk sample and electrolytically extracted precipitates, respectively. According to the results, as the sizes of the particles increased the - coherency as well as the compressive strain of the precipitates was reduced and consequently their morphology changed from spherical to cubic, then flower-like, and finally dendritic shapes.
A. Samadi, M. Ghayebloo ,
Volume 34, Issue 2 (Journal of Advanced Materials- Summer 2015)
Abstract
To evaluate the effect of inoculant addition on functionally graded microstructure of centrifugally cast Al-Mg2Si composites, two cylinders of Al-13.8 wt.% Mg2Si with and without the addition of 1 wt.% Al-5Ti-B inoculant were cast in a vertical centrifugal casting machine. The chemical composition, microstructures and microstructural phases of the different radial sections of the cast cylinders were studied using induction coupled plasma (ICP) method, optical/scanning electron microscopes, and X-ray diffractometry, respectively. The results showed that in the inoculant content cylinder, owing to the prevailing thermal regime as well as the specific mode of eutectic solidification in this composite, the titanium and boron compounds were segregated towards the middle layer of the cylinder and caused the formation of primary Mg2Si particles and non-eutectic Al () in this layer. In addition, due to the effect of centrifugal force during solidification, a higher volume fraction of the light primary Mg2Si particles, according to Stocks law, was segregated towards the inner layer of the cast cylinders.
