Showing 14 results for Rafi
B. Sadeghi, H. Sharifi, M. Rafiei,
Volume 3, Issue 1 (Journal OF Welding Science and Technology of Iran 2017)
Abstract
In this research, the microstructure and mechanical behavior of dissimilar joint of AISI 321 stainless steel to ASTM A57CL1 were studied. For this purpose, the GTAW process and ER 308L filler metal with diameter of 1.8 mm were used. In order to study the microstructure and fracture surface of weld samples, optical microscope and scanning electron microscope (SEM) were used. Also, the mechanical behavior of the joint was examined by impact, tension and microhardness tests. It was found that the microstructure of weld metal was austenite with skeletal ferrite. Also in some areas the lacy ferrite was seen. All samples were fractured from ASTM A537CL1 steel with a ductile manner during the tension test. The weld metal indicated high impact energy about 205 J.
B. Sadeghi, M. Shamanian, F. Ashrafizadeh, P. Cavaliere,
Volume 4, Issue 2 (Journal OF Welding Science and Technology of Iran 2019)
Abstract
Solid state joining of powder metallurgy (P/M) processed and sintered by spark plasma sintering through friction stir welding (FSW) was studied. The nanocomposites were prepared via mechanical milling followed by spark plasma sintering. The microstructural and mechanical of the joints were evaluated as a function of the different processing parameters such as rotating and advancing speeds of the tool. The achieved finding revelled that the FSW of the nanocomposites produced by P/M containing bimodal sized Al2O3 reinforcement have a working window are affected by the heat input. The joint evolution revelled that the microstructure and mechanical properties of those was related to the generated heat input during the welding. It is known that dynamic recrystallization (DRX) caused grain size refinement of aluminium into stir zone. Meanwhile, it was revealed that the pinning effect of Al2O3 nanoparticles retarded grain growth of the recrystallized grains caused by dynamic recrystallization (DRX)
I. Rasouli, M. Rafiei,
Volume 4, Issue 2 (Journal OF Welding Science and Technology of Iran 2019)
Abstract
In this research, microstructure and mechanical properties of AISI316 to AISI430 dissimilar joint were investigated. For this purpose, GTAW process using ER316L and ER2209 filler metals with diameter of 2.4 mm was used. The microstructure and fracture surface of the welded samples were characterized by optical microscopy and scanning electron microscopy. Also the mechanical properties of the welded samples were evaluated by tension, impact and microhardness tests. It was found that the microstructure of the welded sample with ER316L filler metal contained Widmanstatten austenite with inter-dendritic and lathy ferrites. Also, in the welded sample with ER2209 filler metal, Austenite phase in ferrite matrix was seen. In tension test, all samples were fractured from AISI430 side of the joint in a ductile manner. ER2209 weld metal indicated low impact energy of about 27 J, while ER316L weld metal indicated higher impact energy of about 43 J. The fracture surface in both welded samples indicated brittle fracture mode. The microhardness of the weld metal of the welded sample with ER316L filler metal was higher than the welded sample with ER2209 filler metal due to the presence of alloying elements, proper distribution of delta ferrite and finer microstructure.
S. Ghaderi, F. Karimzadeh, A. Ashrafi,
Volume 5, Issue 2 ((Journal OF Welding Science and Technology) 2020)
Abstract
In the present study, the effect of time and base metal microstructure on the Transient Liquid Phase (TLP) bonding of 304L stainless steel was studied. TLP was performed at 1050 0C for 5 and 60 minutes on the coarse grain austenitic and martensitic microstructure using BNi-2 interlayer. To prepare martensitic microstructure, as-received 304L was rolled at -15 0C up to 80% rolling reduction. TEM analysis was proved that the microstructure of 80% rolled samples consisted of two different morphologies of martensite namely as lath-type and dislocation cell type martensite. It was observed that the structure of bonded zone after 5 min has consisted of isothermally solidified zone (ISZ) containing γ solid solution and athermally solidified zone (ASZ) containing complex boride phases. Meanwhile, after 60 min of heating, the structure of bonded zone completely solidifies isothermally. The obtained results also showed that the martensitic microstructure considerably effect on the width of diffusion affected zone (DAZ) which was related to the reversion of martensite to ultrafine grain austenite during heating.
M. Emadi, H. Mostaan, M. Rafiei,
Volume 5, Issue 2 ((Journal OF Welding Science and Technology) 2020)
Abstract
Dissimilar weld joints between stainless steels and nickel based super alloys are extensively used in petrochemical, gas and oil applications. These joints jave great challenges from metallurgical transformations point of view. In this research, microstructural evolutions and corrosion behavior of laser weld joint between Inconel 625 and AISI 430 ferritic stainless steel were investigated. Ferritic stainless steels are less expensive and have magnetic properties in comparison with austenitic stainless steels. Scanning electron microscope and optical microscope were used in order to study the microstructures of weld metal and heat affected zone. It was found that fine dendritic microstructuresare formed in the weld metal which isgrown in a competition manner. An epitaxial growth was observed in the interface between AISI base metal and weld metal. No considerable grain growth was observed in the heat affected zone on Inconel 625. Corrosion resistance of weld joint was investigated in 3.5 % wtNaCl solution using potantiodynamic polarization test. It was concluded that corrosion resistance is increased from AISI 430 base metal toward Inconel 625 base metal.
M.r. Samadi, H. Mostaan, M. Rafiei , M. Salehi,
Volume 6, Issue 1 (Journal OF Welding Science and Technology 2020)
Abstract
Nowadays, aluminum and its alloys have extensive applications in marine and aerospace industrious owing to their excellent properties. Among these alloys, 5xxx series of aluminum alloys have also excellent corrosion resistance, high toughness and strength and also good weldability. Decrease in yield strength and also tensile strength due to the grain growth in the heat affected zone is of the main problems in the welding of these series of Al alloys. In this research work, gas tungsten arc weld joints in two modes i. e. direct current and pulsed current were compared in order to study the effect of this parameter on the microstructure, mechanical properties and corrosion resistance of weld joints. Also, the effect pulsed current parameters such as peak current and basic current were investigated. Microstructural evolutions and fracture surfaces of weld joints were examined by optical microscope and scanning electron microscope, respectively. It was found that the fracture behavior of all joints is in a ductile manner. Also, tensile test and electrochemical polarization were conducted in order to study the mechanical properties and corrosion behavior of weld joints.
M. Rafi, H. Sabet, V. Abouei Mehrizi,
Volume 7, Issue 1 (Journal OF Welding Science and Technology 2021)
Abstract
In this project, joining Ti-6Al-4V and AISI 304 dissimilar plates by laser-spot-welding method has been studied. In this regard, Ti-6Al-4V and AISI 304 plates, with a thickness of 0.7 and 0.5 respectively, were lap-welded using an interlayer of 0.2 & 0.3 mm copper and silver (pure silver). The process was done by 400Watt pulsed laser (Nd:YAG) using oncentric spot welding with 4mm diameter circles as lap welding. Once the spots were created, they got studied and surveyed first by eye inspection, then by optic metallography inspection and finally, by tensile strength and SEM; of course, if cracks were not detected on joining. The results proved copper a better interlayer compared to silver: no joining occurred while using silver as an interlayer for 3 milliseconds, and replacing the upper metal didn’t change the outcome. The best joining result was observed when AISI 304 was placed above (near the laser), copper plate interlayer was used in 7 milliseconds, with 15 Hz frequency, 10.7 J heat input and 1.5 KW peak-power. This way, sheer strength equaled 160 MPa and micro hardness equaled 504 HV.
Dr Seyed Mahdi Rafiaei, Eng. Gholamhosein Eslami,
Volume 7, Issue 2 (Journal OF Welding Science and Technology 2022)
Abstract
In this research, Ti-6Al-4V alloy sheet with a thickness of one millimeter with butt joint design was welded by tungsten-gas arc welding process using pulse current (PCGTAW) and using AMS 4954G filler metal. In this study, the effect of pulse system frequency on microstructure and mechanical properties was investigated by optical microscopy, Vickers hardness and tensile strength tests. In the non-frequency welding sample, due to the lack of pulse current and lower cooling rate of the molten pool, the formation of large amounts of soft phases of the Weidmann-Statten layer in the weld metal region is possible. Finally, in this method, the lowest average hardness of 341 Vickers was obtained. The experimental results showed that using pulsed current and increasing the pulse frequency up to 450 Hz increased the cooling rate of the molten pool, followed by increasing the amount of martensitic phase α 'in the form of a basket in the weld metal region and finally increasing the average microhardness in this region. In other words, using the maximum frequency led to a significant increase in hardness up to 367 Vickers in the weld zone. Finally, using the tensile strength test, it was shown that in all the samples, failure occurred from the base metal area, which was a very good phenomenon due to the proper welding quality of the samples.
Majid Aslani, Mahdi Rafiei,
Volume 7, Issue 2 (Journal OF Welding Science and Technology 2022)
Abstract
In this study, in order to modify the weld structure obtained from repair welding of AZ91C magnesium alloy and improvement of tensile strength, input parameters such as current intensity and preheating temperature were optimized for this alloy. T6 heat treatment was separately done befor and after the welding to homogenize the microstructure and improvement of the mentioned properties. Using variance analysis, the accuracy of the models was checked and analyzed. Optical microscopy, scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS) and tensile tests were used to characterize the microstructure and mechanical properties of the repaired parts. The results of microstructural studies showed that the samples 2 (samples that were subjected to T6 heat treatment before and after welding) had continuous precipitates which these precipitates affected the strength due to the interruption of more slip planes and creating stronger barriers in the path of dislocations, resulting the better mechanical properties as compared with samples 1 (samples that were subjected to heat treatment only after welding). Also, by plotting response surface graphs and level diagrams, the highest tensile strength for samples 1 was observed at preheating temperatures of 493 to 513 K and current intensities of 80 to 90 A, and for samples 2 at temperatures of 513 to 553 K and current intensities of 100 to 110 A.
A. Lalpour, M. Mosallaee, A. Ashrafi,
Volume 9, Issue 1 (Journal OF Welding Science and Technology 2023)
Abstract
In the present study, friction stir processing (FSP) technique was carried out on the AA2024 sheet at different traverse speed (63 to 250 mm/min) and rotation speed (315 to 800 rpm). The temperature and grain size of stirred zone (SZ) were measured and their relationship was analyzed and effect of FSP parameters on the grain size of SZ was determined. Experiment and analytical investigations revealed that SZ grain size complies the exponential temperature-dependent relationship and can be defined the mathematical equation. Calculations indicate that a change in operational variables (rotation and traverse speeds) makes no variation in strain rate, and it is constant.
L. Gadami Domabi, S. M. Rafiaei, S. Jahanbazi Gojani,
Volume 9, Issue 1 (Journal OF Welding Science and Technology 2023)
Abstract
In this paper the production of chitosan and polylactic acid polymer scaffolds containing zinc oxide particles was carried out through the 3D printer method. Zinc oxide particles were processed through combustion synthesis method. According to the XRD results, the produced oxide has a high phase purity, and the evaporation of volatile impurities and the increase of crystallinity happened via performing the calcination process. In the X-ray diffraction pattern of PLA/ZnO/Chitosan, the broad peak in the range of 10-25 degrees indicates the amorphousness of the background polymer, and with the addition of ZnO, sharp and powerful peaks have appeared in the graph. The SEM images of zinc oxide synthesized by combustion method also showed that the size of ZnO nanoparticles is approximately 50 nm, while after the calcination heat treatment, the size of the particles increased greatly and reached an average size of 130-160 nm. Finally, the microscopic images obtained from the surface of scaffolds possessing 10% zinc oxide, 5% chitosan and polylactic acid showed that by optimizing the 3D printer, ZnO particles are uniformly dispersed in PLA/Chitosan polymer field.
Behnam Heidari-Dehkordi, Mahdi Rafiei, Mahdi Omidi, Mohsen Abbasi-Baharanchi,
Volume 9, Issue 2 (Journal OF Welding Science and Technology 2024)
Abstract
In this study, 316L stainless steel and WC-10Co cermet were bonded by transient liquid phase process with BNi-2 interlayers with different thicknesses of 25 and 50 μm. The bonding process was conducted at 1050 °C for 1, 15, and 30 min. After bonding, the microstructure of the joints was examined using optical microscopy and scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy. Microhardness and tensile-shear tests were also performed to study the mechanical properties of the bonded samples. Microstructural analyses revealed that the formation mechanism of the solidified region in all samples was isothermal solidification, resulting in an isothermal solidification zone upon bonding. Additionally, the only phase present in the isothermal solidification zone was a nickel-based solid solution. In the diffusion-affected zone of the steel base material, complex borides formed regardless of the interlayer thickness. In the diffusion-affected zone of the WC-Co material, a brittle eta phase formed. Microhardness tests indicated that the maximum hardness in all samples was approximately 1100 Vickers, which was attributed to the presence of hard WC particles in the WC-Co base material. Furthermore, the highest tensile-shear strength, approximately 240 MPa, was observed in the bonded sample for 15 min with 50 μm thickness interlayer.
Farzad Shahin, Ehsan Baharzadeh, Mahdi Rafiei, Hossein Mostaan,
Volume 9, Issue 2 (Journal OF Welding Science and Technology 2024)
Abstract
In this study, formation of Fe3Al and (Fe,Cr)3Al intermetallic compounds and the effect of Cr on microstructural and mechanical properties of Fe-Al cladding system such as hardness and wear resistance, were evaluated. For this purpose, first, iron and aluminum powders were mixed without chromium powder and in the second stege with the addition of chromium powder in high energy planetary ball mill, and Fe3Al and (Fe,Cr)3Al intermetallic compounds were synthesized. The preplaced powders were cladded on the surface of CK45 steel using gas tungsten arc welding process. The microstructure, formed phases and properties of the cladded layers were studied by optical microscope, scanning electron microscope, X-Ray Diffraction, micro and macro hardness, energy dispersive X-ray spectroscopy (EDS) and pin on disk wear test at temperatures of 25, 250, and 500 ᵒC. It was found that the microstructure of Fe-Al binary cladding contained Fe3Al dendrites with non-epitaxial growth. This non-epitaxial growth resulted from the difference in the chemical composition of the coating and the substrate at the interface between the coating and the substrate, which caused the formation of new crystals at the interface. However, the microstructure of Fe-Al-Cr ternary cladding contained martensitic blades within (Fe,Cr)3Al matrix. The results of hardness tests revealed that the hardness of ternary cladding is twice as compared with the binary cladding (30 and 60 HRC for binary and ternary claddings, respectively). Also it was found that the presence of Cr element in Fe-Al cladding improved the wear resistance of deposited layers. The predominant wear mechanism of Fe3Al pin was adhesive, while for (Fe,Cr)3Al pin moreover adhesive wear, micro-plowing abrasive wear was also seen. The mass losses of both pins were maximum at ambient temperature and minimum at temperature of 500 oC.
H. Zeidabadinejad, M. Rafiei, I. Ebrahimzadeh, M. Omidi, F. Naeimi ,
Volume 10, Issue 1 (Journal OF Welding Science and Technology 2024)
Abstract
In this research, the transient liquid phase bonding of St52 carbon steel to WC-Co cermet using a copper interlayer with 50 μm thickness was done. For this purpose, samples were jointed to each other at a constant temperature of 1100 ºC and bonding times of 1, 15, 30, and 45 min. The microstructure of the joints was examined using an optical microscope and scanning electron microscope equipped with energy-dispersive X-ray spectroscopy. XRD analysis was also used to investigate the effect of bonding on the phase changes of the bonding area. Microhardness and tensile shear tests were also conducted to study the mechanical properties of the samples. Microstructural investigations showed the formation of three different zones including isothermal and athermal solidification zones and DAZ in the WC-Co base material side, which determine the characteristics of the samples. The isothermal solidification zone contained a Fe-rich solid solution and the athermal solidification zone contained a Cu-rich solid solution. η phase was not formed in the DAZ of WC-Co cermet at bonding times of 1 and 15 min. This phase was formed in the DAZ of WC-Co cermet by increasing the bonding time to 30 and 45 min. The microhardness studies showed that all samples had the same trend. Maximum microhardness was 1100 HV which was related to WC-Co base cermet and the lowest microhardness was about 220 HV which was related to steel base metal. Also, the maximum tensile-shear strength of the bonded samples was about 180 MPa for a bonded sample at a bonding time of 15 min, which was due to the increase in the volume fraction of iron-rich solid solution, as well as proper microstructural continuity and the presence of an optimal amount of copper-rich phase in the microstructure.
