Showing 3 results for Ehteshamzadeh
Sh. Shahriari, M. Ehteshamzadeh,
Volume 10, Issue 1 (march 2013)
Abstract
Abstract: Plasma electrolytic oxidation (PEO) technique was used to prepare ceramic coatings on the casted aluminum alloys containing ~5 and ~9.5 wt.% Mg. The applied voltage was controlled at 450V and 550V for evaluating the effect of this main parameter, as well as, magnesium content of the substrate on the microstructure and electrochemical corrosion behavior after PEO treating. The results of X-ray diffraction confirmed formation of galumina and MgSiO3. It was found that higher applied voltage caused fewer and minor discharge channels which led to higher corrosion resistance. Also, increasing of magnesium content of the substrate caused decreasing of polarization resistance, which could be associated to the formation of MgSiO3.
M. Mohammadnejad, M. Ehteshamzadeh, S. Soroushian,
Volume 11, Issue 2 (June 2014)
Abstract
Microstructure and corrosion performance of admiralty brass (ADB) and aluminum brass (ALB) alloys after
passing different annealing heat treatments were investigated using optical and scanning electron microscope, energy
dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), DC polarization measurements and electrochemical
impedance spectroscopy (EIS). The results showed that heat treating of ALB caused gradient in aluminum
concentration across the grains whose increased with increasing of annealing temperature. On the other hand,
corrosion current density (i
corr) of ADB in 3.5%NaCl media decreased with increasing of recrystallization, while ALB
showed corrosion behavior inconsistent with ADB. The impedance measurements showed that corrosion rate of ADB
decreased with increasing of exposure time from 0 to 15 days which could be related to the formation of SnO
2
surface
film and the Sn-rich phases. While polarization resistance of ALB decreased by passing days in the corrosive media
which could be associated to establishing of differential aluminum concentration cells.
H. Nazemi, M. Ehteshamzadeh,
Volume 12, Issue 3 (September 2015)
Abstract
Compression springs were prepared from Cr-Si high strength spring steel and coated with pure Zn and ZnNi by electroplating process. The effect of baking after electroplating as well as applying an electroless nickel
interlayer on the fatigue and fatigue corrosion of the springs was investigated. The results were analyzed using weibull
statistical model. A considerable improvement (8%) in fatigue life of the electroplated springs with Zn-Ni was observed
in the presence of Ni interlayer. In addition, baking of these electroplated springs improved fatigue life by 4%. The
fatigue life under salt spraying conditions, however, has demonstrated remarkable reduction by 40%, 34% and 30%
for Zn-Ni plating, backed and unbaked Zn-Ni plating containing Ni interlayer, respectively
