Papers by Mahmood Sharifitabar
International Journal of Applied Ceramic Technology
International Journal of Applied Ceramic Technology, Apr 5, 2022
Microchemical Journal, 2022
International Journal of Refractory Metals and Hard Materials, 2014
The aim of the present study was to investigate the effect of Fe additions on combustion velocity... more The aim of the present study was to investigate the effect of Fe additions on combustion velocity and phases that are formed after synthesis in the TiO 2 -Al-C system. Before experimental tests, thermodynamic calculations were performed to determine the range that Fe can be added to the reaction and remain self sustaining. According to the Merzhanov criterion, if the amount of Fe is lower than 53.13 wt.%, the adiabatic temperature of the reaction is higher than 1800 K and therefore the reaction proceeds in the self sustaining mode. But, experimental observations showed that the reaction became unstable when the amount of Fe was changed from 15 to 20 wt.%, which was considerably lower than that was predicted by thermodynamic calculations. X-ray diffraction analysis indicated that Fe 3 Al, TiC and Al 2 O 3 are the main phases formed in the products and additions of Fe decreased the lattice parameter of TiC. Also, Raman spectroscopy analysis showed that at higher Fe contents, oxygen dissolved in the TiC crystal structure leading to the formation of titanium oxy-carbide with lower lattice parameter and residual un-reacted carbon in the products. The adiabatic temperatures for the reactions containing 15 and 20 wt.% Fe estimated using the thermodynamic data of the new products were in conformance with the Merzhanov criterion and experimental observations. Scanning electron microscopy examinations showed that the addition of Fe decreased TiC particle size and changed their growth controlling mechanism.
Ceramics International
Abstract MgAl2O4‒W and MgAl2O4‒W‒W2B composite powders were obtained rapidly in a single step by ... more Abstract MgAl2O4‒W and MgAl2O4‒W‒W2B composite powders were obtained rapidly in a single step by self-propagating high-temperature synthesis of WO3‒Mg‒xAl2O3 and WO3‒B2O3‒Mg‒yAl2O3 systems. The addition of various Al2O3 contents (x and y-values) to the starting materials was considered as the main synthesis parameter. Thermodynamic calculations revealed that the adiabatic temperature of both systems was decreased with increasing Al2O3 content. The XRD results indicated that after acid leaching of the WO3‒Mg‒xAl2O3 combustion products, W and MgAl2O4 were formed as the main phases and WO2, MgWO4 and Al2O3 as the minor constituents in the final composite. On the other hand, MgAl2O4‒W composites were synthesized in the WO3‒B2O3‒Mg‒yAl2O3 system at y
In this research, titanium carbo-nitride coatings were synthesized on the surface of Ti-6Al-4V al... more In this research, titanium carbo-nitride coatings were synthesized on the surface of Ti-6Al-4V alloy by nitro-carburizing route and the detachment mechanism of the coatings were investigated. For this purpose, rectangular blocks were embedded in a carbon containing graphite cup. Then, the cup was placed in a tubular furnace containing nitrogen gas. After coating in different temperatures between 1200 and 1400 ̊C for 20 to 60 min soaking times, structure and microstructure of the coatings were investigated by X-ray diffraction, Raman analysis and scanning electron microscope equipped with energy dispersive spectroscopy (EDS). Moreover, the effect of coatings on the corrosion resistance of the alloy in an aqueous solution containing 5.2 mol HCl, 3.2 mol HNO3 and 3.2 mol HF was investigated. Results showed that the maximum thickness of the titanium carbo-nitride coating for the sample treated at 1400 ̊C for 60 min was about 50 μm. However, the possibility of coating detachment increase...
Transactions of Nonferrous Metals Society of China
Advanced Powder Technology
International Journal of Minerals, Metallurgy, and Materials, 2016
In this research, resistance upset butt (RUB) welding of 304 austenitic stainless steel and effec... more In this research, resistance upset butt (RUB) welding of 304 austenitic stainless steel and effect of welding power and upset pressure on microstructure and mechanical properties of the joint were investigated. Microstructure of the weld was studied using scanning electron microscopy. X-Ray diffraction analysis was used to evaluate the phase(s) that formed in the joint interface and HAZ. Also tensile strength test were performed. Results showed that there were three different zones in different distances from the joint interface and delta ferrite phase has formed in these regions. There was no precipitation of chromium carbide in the HAZ. The strength of the joint decreased with welding power. Increasing the upset pressure also had considerable influence on tensile strength of the joint.
Materials & Design, 2015
ABSTRACT 304 austenitic stainless steel reinforced by Al2O3 particles was prepared by microwave a... more ABSTRACT 304 austenitic stainless steel reinforced by Al2O3 particles was prepared by microwave assisted self-propagating high temperature synthesis process using the Fe2O3Cr2O3NiOAlFe reaction system. Furthermore, effects of mechanical activation of the reactants and the addition of 21.2 wt.% extra Al to the chemical composition of the reactants on the chemical composition of the produced stainless steel was investigated. Atomic absorption spectroscopy analysis results indicated that by the addition of extra Al to the reactant mixture and using 30 minute mechanical activation, stainless steel containing 17.27 wt.% Cr and 7.73 wt.% Ni could be produced with its chemical composition very close to the chemical composition of 304 stainless steel. X-ray diffraction analysis showed that the stainless steel contains nanostructured austenite and ferrite phases. Also microstructural characterizations indicated that there is a uniform distribution of black particles in the steel matrix. Energy dispersive spectroscopy analysis showed that these particles are composed of Al and O elements while the matrix contains Fe, Cr and Ni elements. The presence of Al2O3 particles and nanostructure matrix improved the hardness and therefore the wear properties of the composite in comparison with the wrought 304 stainless steel plate.
Surface and Coatings Technology, 2013
ABSTRACT In the present study Ti(C, N) ceramic layer was synthesized on the surface of Ti–6Al–4V ... more ABSTRACT In the present study Ti(C, N) ceramic layer was synthesized on the surface of Ti–6Al–4V alloy by pack nitro-carburizing method to improve surface properties of this alloy. Rectangular blocks were placed in a carbon contained graphite cup and heat treated in a nitrogen atmosphere at different temperatures and soaking times. Phase analysis results indicated that higher treatment temperatures led to increase carbon concentration in Ti(C, N) phase. Almost uniform layer with very high hardness compared to the base material was synthesized and the thickness of the layer increased with increasing treatment time and temperature. Also, corrosion resistance of the alloy was improved dramatically after pack nitro-carburizing process. In some samples, separation of a layer from base material was observed and a suggested mechanism for this phenomenon was declared.
International Journal of Refractory Metals and Hard Materials, 2014
The aim of the present study was to investigate the effect of Fe additions on combustion velocity... more The aim of the present study was to investigate the effect of Fe additions on combustion velocity and phases that are formed after synthesis in the TiO2-Al-C system. Before experimental tests, thermodynamic calculations were performed to determine the range that Fe can be added to the reaction and remain self sustaining. According to the Merzhanov criterion, if the amount of Fe is lower than 53.13 wt.%, the adiabatic temperature of the reaction is higher than 1800 K and therefore the reaction proceeds in the self sustaining mode. But, experimental observations showed that the reaction became unstable when the amount of Fe was changed from 15 to 20 wt%, which was considerably lower than that was predicted by thermodynamic calculations. X-ray diffraction analysis indicated that Fe3Al, TiC and Al2O3 are the main phases formed in the products and additions of Fe decreased the lattice parameter of TiC. Also, Raman spectroscopy analysis showed that at higher Fe contents, oxygen dissolved ...
Transactions of Nonferrous Metals Society of China, 2012
The dissimilar joining of CP-copper to 304 stainless steel was performed by gas tungsten arc weld... more The dissimilar joining of CP-copper to 304 stainless steel was performed by gas tungsten arc welding process using different filler materials. The results indicated the formation of defect free joint by using copper filler material. But, the presence of some defects like solidification crack and lack of fusion caused decreasing tensile strength of other joints. In the optimum conditions, the tensile strength of the joint was 96% of the weaker material. Also, this joint was bent till to 180º without any macroscopic defects like separation, tearing or fracture. It was concluded that copper is a new and good candidate for gas tungsten arc welding of copper to 304 stainless steel. 摘 要：采用不同焊丝对工业纯铜和 304 不锈钢进行钨极氩弧焊接。结果表明，采用铜做焊丝时，焊缝无任何缺 陷生成，而采用 304 不锈钢和 Ni−Cu−Fe 合金为焊丝材料时，焊缝中有凝固裂纹和未熔化区存在。在最优条件下， 焊缝的抗拉强度能达到铜材的 96%。焊缝在弯曲到 180°下也没有分离、撕裂和断裂等现象发生。这表明铜是一种 较好的工业纯铜与 304 不锈钢 GTA 焊的焊丝材料。 关键词：钨极氩弧焊；工业纯铜；304 不锈钢；异种材料连接；显微组织；力学性能 (Edited by YUAN Sai-qian)
Materials & Design, 2010
In this research, joining austenitic to martensitic stainless steels and effect of welding power ... more In this research, joining austenitic to martensitic stainless steels and effect of welding power on microstructure and mechanical properties of the joint were investigated. Microstructure of the weld was studied using optical microscopy (OM) and scanning electron microscopy (SEM). Energy dispersive spectroscopy (EDS) linked to SEM was used to determine chemical composition of phases and distribution of chromium (Cr), nickel (Ni) and iron (Fe) at the joint interface. Microhardness and tensile strength tests were performed. Finally fracture surface of samples were studied by SEM. Results showed that an interlayer composed of 80% ferrite and 20% martensite has formed at the joint interface and there were three different zones in the heat affected zone (HAZ) of two steels. Different forms of austenite phase including widmanstatten austenite (W c ), allotriomorphic austenite (A c ) and intergranular austenite (I c ), delta ferrite (d-ferrite) and chromium carbide (Cr 23 C 6 ) have formed in the HAZ of austenitic stainless steel. Fractography of tension samples indicated that in all samples fracture occurred in austenitic stainless steel HAZ. The strength and hardness of the joint increased and HAZ length decreased with increasing of welding power.
Composites Part B-engineering, 2011
In this research, microstructures and hardness profiles across the interface of friction stir wel... more In this research, microstructures and hardness profiles across the interface of friction stir welded joints between monolithic 2024-T4 aluminum alloy (AA) and Al/Mg 2 Si metal matrix cast composite (MMC) and effects of one and two welding passes on these parameters were investigated. Results showed that there were complicated patterns of materials flow in the stir zone (SZ) especially in samples welded in two passes. This region was free of defects like voids and tunnel defects in samples welded in one pass. But some defects were formed in samples welded in two passes. Stirring caused fragmentation and rearrangement of Mg 2 Si large particles in the stir zone and thermo mechanically affected zone (TMAZ) of MMC, respectively. Eutectic phase has formed on the grain boundaries of 2024 AA in thermo mechanically affected zone due to high heat input to the joint area during welding. In samples welded in one pass, hardness increased from the base metal to the stir zone on the MMC side, reached a maximum in the middle of the joint interface and decreased at about 2 mm away from the joint interface center on 2024 AA side. But, hardness variation in the sample welded in two passes was complicated and there was alternating decrease and increase in hardness value at the joint interface.
Materials & Design, 2011
In the present study, friction spot welding or refill friction stir spot welding was performed to... more In the present study, friction spot welding or refill friction stir spot welding was performed to consolidate dissimilar AA5754 Al and AZ31 Mg alloys. The intermetallic compounds of Al 12 Mg 17 and Al 3 Mg 2 were primarily found in the weld, distributed at the interface between the base materials and in the Al top sheet. The distribution of the intermetallic compounds and the interfacial area between the base materials affect the lap shear strength of the weld. It is concluded that the material flow induced by tool movement plays an important role in both the distribution of the intermetallic compounds and the interfacial area between the base materials.
Materials & Design, 2011
Gas atomized Mg-Zn 4.3 Y 0.7 (at%) alloy powders were consolidated by using a magnetic pulsed com... more Gas atomized Mg-Zn 4.3 Y 0.7 (at%) alloy powders were consolidated by using a magnetic pulsed compaction (MPC) process, and obtained by rapid solidification not to lose the fine microstructure during the generally conducted thermal consolidation process. MPC is known as one of the most rapid pressing process with the GPa range. The effects of the discharging voltage and thermal pressure on the microstructure, hardness, density and compressive strength were investigated. The experimental results showed that the density increased with increasing the voltage although the sample MPCed still consists of pores especially between the powder boundaries even at the maximum pressure of this investigation. The density was improved further up to 96% to the cast value by the MPC at the maximum voltage. Uniform and fine microstructure formed in the alloy powders as atomized was almost maintained even after the thermal MPC.
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Papers by Mahmood Sharifitabar