Showing 6 results for M.R
Yahosseini M.r.s., Simchi A., Varahram N., Davami P.,
Volume 2, Issue 1 (Oct 2005)
Abstract
In the present work, a model was proposed to predict the thermal history during rapid solidification (RS) of metal droplets in the gas atomization process. The classical theory of heterogeneous nucleation was based on Newtonian heat flow and enthalpy method. Solving the governing numerical equations by the finite difference method (FDM) gave up the opportunity of analyzing the temperature-time history of the droplets during cooling in the RS process. Here, cooling in the liquid state, nucleation and recalescence, segregated solidification, eutectic solidification and cooling in the solid state were considered. To verify the model, the gas atomization of Al-4.5% Cu alloy was studied and the results were compared with the Shukla's model [1]. Convincing agreement was obtained between the predicted undercoolings and the experimental results reported previously.
Fatemi Nayeri S.h.r., Aboutalebi M.r., Vahdati Khaki J.,
Volume 3, Issue 1 (Oct 2006)
Abstract
A mixture of Tio2+Al+C powders was mechanically activated using a planetary ball mill under different milling conditions wherein the milled powders were further subjected to combustion synthesis to produce TiC+Al2O3 composite. The mechanically alloyed powders were characterized by X-Ray diffraction analysis and TEM investigations. XRD analysis of milled powder mixture showed no significant reaction between TiO2, Al and C while a significant amorphization of powder mixtures was observed. TEM analysis indicated the formation of a composite structure of powder particles after milling. The subsequent thermal treatment of the milled powder mix showed that the milling of initial powder mixture under dry environment using mixed large and small balls had a great effect on reaction efficiency and yielded to the highest TiC + Al2O3 ratio in the synthesized products.
B. Pourgolmohammad, S.m. Masoudpanah, M.r. Aboutalebi,
Volume 15, Issue 2 (June 2018)
Abstract
In this work, the different fuels (citric acid, glycine and urea) were used for solution combustion synthesis of CoFe2O4 powders. X-ray diffraction, Raman spectroscopy, electron microscopy and vibrating sample magnetometry techniques were employed for characterization of phase evolution, cation distribution, microstructure and magnetic properties of the as-combusted CoFe2O4 powders. Single phase CoFe2O4 powders with partially inverse structure in which the Co2+ cations are distributed in both tetrahedral and octahedral sites were synthesized by the citric acid, glycine and urea fuels. The as-combusted CoFe2O4 powders by the citric acid fuel exhibited the highest inversion coefficient. The crystallite size of the as-combusted CoFe2O4 powders synthesized by urea fuel was 15 nm, increased to 41 and 52 nm for the glycine and citric acid fuels, respectively. Furthermore, the solution combusted CoFe2O4 powders showed ferromagnetic behavior with saturation magnetization of 61.9, 63.6 and 41.6 emu/g for the citric acid, glycine and urea fuels, respectively. The high crystallinity and particle size of the as-combusted CoFe2O4 powders using glycine fuel led to the highest magnetization and the moderate coercivity.
R. Zarei Moghadam, M.h. Ehsani, H. Rezagholipour Dizaji, M.r. Sazideh,
Volume 15, Issue 3 (September 2018)
Abstract
In this work, Cadmium Telluride (CdTe) thin films were deposited on glass substrates at room temperature by vacuum evaporation technique. The deposited CdTe thin films were characterized by X-ray diffraction, UV-Visible spectroscopy and Field emission scanning electron microscope (FESEM) techniques. Structural studies revealed that the CdTe films deposited at various thicknesses are crystallized in cubic structure. The results showed the improvement of the film crystallinity upon grain size increment. Optical constants such as refractive index (n), extinction coefficient (k), real and imaginary parts of dielectric constant, volume energy loss function (VELF), and surface energy loss function (SELF) were calculated using UV-Vis spectra. In addition, band gap and Urbach energies were calculated by Tauc and ASF methods. The band gap energy of the specimens was found to decrease from 1.8 to 1.4eV with increasing the thickness of films. The absorption coefficient, computed and plotted versus the photon energy (hν) and tailing in the optical band gap, was observed which is understood based on Urbach law. Urbach energy variation from 0.125 to 0.620 eV in the samples with higher thicknesses is concluded.
M.r. Tavakoli Shoushtari, M. Goodarzi, H. Sabet,
Volume 15, Issue 4 (December 2018)
Abstract
In this study, the microstructure, hardness, and dry sliding wear behavior of the hardfaced layers made by a cored wire Fe-B-C-Ti alloy were investigated. St37 steel was used as the substrate and the deposition of the hardfaced layers was conducted by the flux cored arc welding (FCAW) process under single-, two-, and three-pass conditions. Dry sliding wear tests were performed by a pin-on-disk apparatus, based on ASTM-G99, at room temperature (250C) at the normal applied loads of 50, 100, and 150 N with a constant speed of 0.08 m/s for a sliding distance of 1000 m. The microstructural and phase analyses were carried out by field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD), respectively. The results showed that the hardfaced layer produced by the single-pass process contains TiC rectangular phase distributed within a matrix containing ferrite and the eutectic of (α-Fe2B). But, the hardfaced layers produced by the two- and three-pass process contain TiB2 hexagonal phase in addition to TiC, which prevents the formation of detrimental FeB phase around Fe2B and reduces the number of micro-cracks. Moreover, the sample hardfaced by the three-pass process had the best wear resistance due to the greater hardness resulted from the higher amounts of TiC and TiB2 phases. In addition, increasing the number of passes has led to the reduction of wear rate at all the three applied loads. At the applied load of 100 N, the wear mechanism for the all three hardfaced samples was an oxidation wear. However, at the applied load of 150 N, the wear mechanism was a combination of oxidation and delamination.
Krishnakumar K, Rajamanickam M.r,
Volume 23, Issue 3 (September 2026)
Abstract
Track rollers used in bucket wheel excavators are subjected to repeated mechanical loading in an environment where abrasive particles, moisture and corrosive contaminants can accelerate surface deterioration. The present study examines the mechanical, electrochemical and tribological behaviour of GS‑42CrMo4V cast steel used for this application. The material w::as char::acterized through chemical composition analysis, microhardness measurement, tensile testing and fractographic examination. Its corrosion behaviour was further evaluated in 3.5 wt.% NaCl and acidic HCl and H₂SO₄ solutions using potentiodynamic polarization and electrochemical impedance spectroscopy, while three-body abrasion and reciprocating wear tests were carried out to assess its resistance to material loss under different contact conditions. The bottom roller exhibited an average microhardness of 430 HV, compared with 314.2 HV for the roller pin. Tensile and fractographic observations indicated good mechanical performance, although localized damage features were observed on the fractured surfaces. The electrochemical results showed that the material performed better in the neutral chloride solution than in the acidic media. In 3.5 wt.% NaCl, the corrosion current density and corrosion rate were 1.597 μA cm⁻² and 0.487 mpy, respectively, whereas the acidic solutions produced considerably higher corrosion activity. The wear tests confirmed that high hardness alone did not prevent material removal under abrasive and sliding contact. Abrasive action, plastic deformation and localized adhesive interactions contributed to surface degradation under the investigated conditions. The results therefore indicate that, despite its favourable hardness and mechanical characteristics, GS-42CrMo4V remains susceptible to degradation in aggressive acidic environments and under severe abrasive and sliding conditions. The observed behaviour points to the need for further improvement in material processing, surface condition, corrosion protection and the control of abrasive particle ingress. These findings provide a basis for understanding the service-related limitations of the material and for improving the durability of track rollers used in mining equipment.
