M. Eshraghi Kakhki, A. Kermanpur, M. A. Golozar,
Volume 30, Issue 1 (Jun 2011)
Abstract
In this work, a 3D thermo-microstructural model was developed to simulate the continuous cooling of steel. The model was employed for simulation of cooling process of the gears made from a plain carbon steel (AISI 1045) and a low alloy steel (AISI 4140). Temperature-dependent heat transfer coefficients for two different quenching media were evaluated by experimental and computational methods. The effects of latent heat releases during phase transformations, temperature and phase fractions on the variation of thermo-physical properties were investigated. The present model was validated against cooling curve measurements, metallographic analysis, and hardness tests, and good agreement was found between the experimental and simulation results. This model was used to simulate the continuous cooling process and to predict the final distribution of microstructures and hardness in steel gears.
M. Eshraghi, Z. Mosleh, M. Rahimi,
Volume 38, Issue 1 (Journal of Advanced Materials-Spring 2019)
Abstract
In this investigation, the structural and magnetic properties of Cr and Zn substituted Co ferrite with the general formula Co1-xZnxFe2-xCrxO4 (x= 0.1, 0.3, 0.5, 0.7) as prepared by sol- gel method were studied. The structural, morphological and magnetic properties of the samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Scanning electron microscopy (SEM) and Vibrating sample magnetometer (VSM). XRD measurements along with the Rietveld refinement indicated that the prepared samples were single phase with the space group of Fd-3m. Results of SEM images also showed that the particles were in the nanosize range. Also, the magnetic properties of the samples indicated that the magnetization was first decreased, reaching the minimum value for x=0.1 sample; then it was increased. This behavior was related to the cation distribution at the tetrahedral and octahedral sites. Moreover, coercivity was significantly decreased with increasing the doping level due the decrease of magnetocrystalline anisotropy because of the nonmagnetic Zn ion substitution.
