Showing 6 results for In-Situ
M. F. Najafabadi and M. A. Golozar,
Volume 23, Issue 1 (7-2004)
Abstract
In this research work, the possibility of semi industrial production of Al-TiB2 and Al-ZrB2 composites, using reactive slag in a flame furnace have been investigated. For this purpose, commercial pure aluminum and powder mixture of TiO2 (ZrO2) , KBF4 and Na3AlF6 were used. The results showed that using a proper ratio of slag forming materials as well as proper amounts of the above-mentioned compounds make it possible to produce good quality Al-TiB2 and Al-ZrB2 compounds employing the conventional melting equipment such as a flame furnace.
F. Mirarabshahi, A. Mashreghi, M. Kalantar, M. Mosalaei,
Volume 35, Issue 4 (2-2017)
Abstract
In this study, fabrication of an in-situ composite through aluminothermic combustion synthesis in An Al–V2O5-NiO system was investigated. Therefore, Al, V2O5 and NiO powders with stoichiometric ratio of 11:1:1, respectively, were milled for an hour and finally the mixtures were compressed. In order to investigate the temperatures of phase transformations, Differential Thermal Analysis (DTA) was utilized. Heat treatment was applied on the raw samples according to their peak temperatures treated in DTA. X Ray Diffraction (XRD) analysis for the samples shows formation of phases such as Al3V and Al3Ni2 at different sintering temperatures. Microstructure and phase analysis showed that during sintering of this sample, Al3V phase was not formed below 700 °C, at 880 °C Al3Ni2 it was formed and after 950 °C, it was transformed to Al4Ni3 phase. In addition, after 950°C, Al3V transformed into Al23V4 phase. Analysis of samples density and hardness showed that, due to increase of volume fraction percentages of reinforcing phase, these two parameters increase as well.
A. Amiri Moghaddam, M. Kalantar,
Volume 36, Issue 1 (6-2017)
Abstract
The aim of this investigation is obtaining WC-Co composite powder from WO3 and Co3O4 by in-situ and carbothermic reduction method using activated carbon as a reducing agent. In this study, cobalt and tungsten oxide powders with 17% carbon (30% more than stoichiometric value) were mixed by ball-milling under atmosphere of argon for 20 hours. Differential Thermal Analysis (DTA) and Thermal Gravimetric Analysis (TGA) results on powder mixture show complete reducing of oxides at 1050°C and forming cobalt carbide and tungsten carbide. Compact samples underwent carbothermic reduction at 1050 °C for different times of 1, 2 and 4 hours with protective layer of alumina and carbon powder mixture with ratio of 1:1. Based on X-Ray Diffraction (XRD) analyses, the best holding time in furnace is 4 hours, in which tungsten reduction and carbonization is completed. XRD evaluation of reduced compacted samples in three conditions of atmosphere protective layer of alumina and carbon powder mixture with ratio of 1:1, protective foil of refractory steel and argon, shows that unreduced oxides and extra phases are present in argon atmosphere and protective foil of steel but not in alumina and carbon mixture layer. The measurement results of physical and mechanical properties on the sintered composite sample in heating rate of 5 °C /min to temperature 1500 °C and the holding time of 2 hours under a shielding layer of alumina and carbon shows obtaining the optimal properties (Pr=80%, KIC=8.1 MPa , MHV=15.67GPa) comparable to that of advanced and costly methods.
M. Khoobroo, A. Maleki, B. Niroumand,
Volume 36, Issue 3 (11-2017)
Abstract
Conventionally, alloying elements are being added to the whole melt; however, in this research in-situ surface alloying of gray cast iron was employed to improve surface properties of the castings. Wires of pure copper with diameters of 0.4 and 0.8 mm were inserted and fixed at bottom of sand molds before melting. Chemical composition analysis revealed the presence of copper from surface to a depth of 1 cm. Microstructural investigations indicated that graphite type changed from A to D and E. Moreover, the content of graphite phase decreased while that of pearlite increased at the surface. Hardness was higher at surface of copper added samples. Wear resistant of the in-situ surface alloyed samples was better than the no-copper added ones.
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.
B. Sharifian, G. H. Borhani, E. Mohammad Sharifi,
Volume 41, Issue 2 (11-2022)
Abstract
In this study, mechanically milled (MM) Al-24TiO2-20B2O3 powder in molten Al7075 matrix was used in order to fabricate in-situ TiB2 and Al2O3 reinforcements in Al7075 matrix. Differential thermal analysis (DTA) examination was adopted to find reaction temperature between milled Al, TiO2, and B2O3 powders. X-Ray Diffraction (XRD) patterns showed the existence of TiB2 and Al2O3 peaks (750 °C at Ar atmosphere) in MM powder. Scanning Electron Microscopy (SEM) results revealed the uniform distribution of TiO2 and B2O3 particles in the aluminum matrix. 6 wt.% MM powder was added to molten Al7075 at 750 °C. The molten Al7075/TiB2-Al2O3 composite was poured in copper mold. The stir casted composites were hot extruded at 465 °C with extrusion ratio of 6:1 and ram speed of 5 mm/s. The microstructures (optical microscopy and TEM) and mechanical properties (hardness and tensile testing) of samples were evaluated. TEM results showed that in-situ TiB2 nanoparticles were formed. The tensile strength of extruded Al7075/TiB2-Al2O3 composite was reached the value of 496 MPa. This result was around four times greater than that of the as cast Al7075 alloy.
