Showing 4 results for Heat Treatment
H. Amiri, S. M. Mirkazemi, A. Beitollahi ,
Volume 34, Issue 2 (7-2015)
Abstract
In this investigation, the effect of heat treatment on magnetic properties of glass and nano-structured cobalt-ferrite glass-ceramic was studied. The glass was synthesized in the system of Na2O-Fe2O3-CoO-B2O3-SiO2. Based on DTA results, heat treatment was done at different times and temperatures. X-ray diffraction pattern of glass-ceramic showed the crystallization of CoFe2O4 and some nonmagnetic phases. The highest magnetization of 11.8 emu/g was obtained for the sample heat-treated for 2 hr at 670C in graphite bed. Average crystallite size of CoFe2O4 in this sample was 50 nm. Scanning Electron Microscopy (SEM) confirmed the formation of cobalt ferrite nanoparticles in the glass matrix.
B. Hassani, F. Karimzadeh, M. Enayati, M. Borouni,
Volume 35, Issue 1 (6-2016)
Abstract
In this study, TIG welding was used to clad and repair the surface of cast AZ91C magnesium alloy. Then, friction stir processing and T6 heat treatment wrer applied on the welded region. Microhardness results showed an improvement in the mean hardness of welded zone and also FSPed zone. Increase in the mean microhardness of the welded zone after T6 heat treatment to the maximum value was also concluded. The results of wear test showed that the wear resistance of the welded area was improved. Further improvement in wear properties was obtained after friction stir processing and T6 heat treatment.
M. Zadali Mohammad Kotiyani, Khalil Ranjbar,
Volume 38, Issue 1 (6-2019)
Abstract
In this research, an in-situ hybrid composite reinforced by Al3Zr and Al3Ti aluminide particles was fabricated by friction stir processing (FSP). The base metal was in the form of a rolled Al 3003-H14 alloy sheet, and zirconium and titanium metal powders were used as the reinforcements. Six passes of FSP were applied. Tensile strength and hardness of the base metal, as well as FSPed samples before and after applying heat treatment, were determined. Microstructural examinations were performed using optical and scanning electron microcopy (SEM), and phase formation was identified by X-Ray diffraction. Microstructural examination revealed that by applying FSP, the prior large and elongated grains of the base metal were converted to the fine and equiaxed grains. It was also observed that chemical reactions occurred at the interface between the aluminum matrix and the metallic powders, forming in-situ aluminides of Al3Zr and Al3Ti. The post annealing heat treatment activated these solid state chemical reactions and more aluminides were formed. It was also found that the heat treated hybrid composite possessed the highest tensile strength and hardness values. The tensile strength in such samples reached 195 MPa, as compared to 110 MPa of the base metal.
M. Shirvani, M. Mashhadi, M. Yosofi,
Volume 38, Issue 4 (1-2020)
Abstract
In this research, solid state carbothermal synthesis of HfB2 Nano powders was investigated. For this purpose, HfO2,H3BO3, carbon active or phenolic resin were used as raw materials for carbothermal reaction. After 2-4 hours of milling the raw materials by a planetary ball in an ethanol media, the mixture was heat dried and pressed in to disks under pressure of 20-30 bar. The disks were then placed in a graphite crucible and heat-treated at 1500–1600 °C for 1 hour under flowing Ar atmosphere. The powder product was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and backscattered electron (BSE) imaging. The heat treatment temperature, amount of boric acid, milling and heat treatment time were recognized as four factors influencing synthesis and size of HfB2 powder particles. SEM images reported irregular morphologies with a particle size of about 2-4 µm for HfB2 powder. The best sample was obtained at a molar ratio of HfO2 : phenolic resin carbon: boric acid = 1:5:5 at 1600 °C after 1 hour of heat treatment. XRD results confirmed synthesis of pure HfB2 with a crystallite size of about 60 nm.
