Loading...
Search for:
fereiduni--eskandar
0.05 seconds
Ultrahigh-strength friction stir spot welds of aluminium alloy obtained by Fe3O4 nanoparticles
, Article Science and Technology of Welding and Joining ; Volume 23, Issue 1 , 2018 , Pages 63-70 ; 13621718 (ISSN) ; Movahedi, M ; Baghdadchi, A ; Sharif University of Technology
Taylor and Francis Ltd
2018
Abstract
The present research was aimed at simultaneous increase in strength and fracture energy of friction stir spot weld of Al-5083 alloy via reinforcing by Fe3O4 nanoparticles. Compared to non-reinforced welds, failure load and fracture energy of reinforced welds increased up to ∼115 and 560%, respectively. These findings were discussed in the light of grain refinement as well as considerable increase in hardness of fracture location due to the presence of sub-micron and nano reinforcing particles (RPs). Fe3O4 nanoparticles were transformed to Al–Fe intermetallics due to their small size and heat generated during the welding process. The stir zone of reinforced welds consisted of three different...
Aluminum/steel joints made by an alternative friction stir spot welding process
, Article Journal of Materials Processing Technology ; Volume 224 , October , 2015 , Pages 1-10 ; 09240136 (ISSN) ; Movahedi, M ; Kokabi, A. H ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
The effect of the rotational speed and dwell time on the joint interface microstructure and tensile-shear strength of friction stir spot welded Al-5083 aluminum/St-12 steel alloy sheets was investigated. Joining of the sheets was performed using an alternative friction stir spot welding (FSSW) process in which the welding tool tip did not penetrate into the lower steel sheet. Rotational speeds of 900 and 1100 rpm were applied in association with the dwell times of 5 to 15 s to weld the samples. Thermal history was recorded during the joining process. Interfacial microstructure, formation of intermetallic compounds (IMCs) at the joint interface and the fracture locations were studied using...
Dissimilar Al/steel friction stir spot welding: To penetrate into the lower steel sheet or not?
, Article Science and Technology of Welding and Joining ; Volume 21, Issue 6 , 2016 , Pages 466-472 ; 13621718 (ISSN) ; Movahedi, M ; Kokabi, A. H ; Sharif University of Technology
Taylor and Francis Ltd
2016
Abstract
There has always been a question about which condition results in superior mechanical properties in friction stir spot welds: (i) when the tool tip penetrates into the lower sheet or (ii) when the tool tip does not touch it. Given the question, the effects of the tool penetration depth were investigated on the microstructure and mechanical behaviour of dissimilar Al-5083/St-12 joints produced by friction stir spot welding (FSSW). Two different processes named as non-penetrating and penetrating FSSW were used. Optical and scanning electron microscopes as well as microhardness and tensile-shear tests were utilised to examine the obtained joints. The results showed that the penetrating process...
Effect of angular position on the quality of dense plasma focus-based additive layer manufactured molybdenum coatings
, Article International Journal of Advanced Manufacturing Technology ; Volume 99, Issue 9-12 , 2018 , Pages 2717-2725 ; 02683768 (ISSN) ; Hosseinzadeh, A ; Nazmabadi, M ; Vosoughi, N ; Sharif University of Technology
Springer London
2018
Abstract
The present research aims at depositing molybdenum on stainless steel substrate using dense plasma focus (DPF) device. The varying parameter was the angular position of substrate surface from the anode tip. The deposited layers were characterized using various analyses such as X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), and microhardness measurements. Microstructural observations revealed that the deposited coatings had rough surfaces containing holes as well as a stripe-featured structure covering the whole surface including the interior regions of the holes and the regions among them....
Effect of dwell time on joint interface microstructure and strength of dissimilar friction stir spot-welded al-5083 and st-12 alloy sheets
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 48, Issue 4 , 2017 , Pages 1744-1758 ; 10735623 (ISSN) ; Movahedi, M ; Kokabi, A. H ; Najafi, H ; Sharif University of Technology
Springer Boston
2017
Abstract
Joining of Al-5083 alloy sheet to St-12 steel sheet was performed using a new friction stir spot welding (FSSW) technique in which the tool pin tip did not enter lower steel sheet. Effect of dwell time on the microstructure and mechanical properties of the joints was studied by various methods including microhardness measurements, shear test, stereo and light microscopy as well as scanning and transmission electron microscopy (SEM and TEM). Results indicated that compared to the conventional FSSW process, stronger joints can be achieved by this FSSW technique. Cross-sectional observation of the failed specimens indicated the occurrence of final fracture from the circumference of the tool pin...
Friction Stir Spot Welding of Al-5083 and St-12 Alloy Sheets
, M.Sc. Thesis Sharif University of Technology ; Kokabi, Amir Hossein (Supervisor) ; Movahhedi, Mojtaba (Supervisor)
Abstract
Friction stir spot welding (FSSW), as a solid state welding process, can be used instead of resistance spot welding (RSW) for dissimilar joining of aluminum and steel sheets due to its advantages over the RSW process including the non-preferential melting of aluminum as well as the formation of thinner intermetallic phases at the joint interface. In the present study, it has been tried out to investigate the effect of rotational speed, dwell time and pin length on the tensile-shear strength of the Al-5083/St-12 friction stir spot welded joints. The pin diameter was 5 mm while the pin lengths of 2.8 and 3.2 were used to weld the samples. Rotational speeds of 800, 900 and 1100 rpm were applied...
Mechanical and electrochemical behaviors of butt-welded high temperature steel pipes
, Article Engineering Failure Analysis ; 2016 ; 13506307 (ISSN) ; Vanini, S. A. S ; Fereiduni, E ; Rokni, M. H ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
In this study, fatigue, corrosion fatigue and electrochemical behaviors of butt-welded A106-B steel pipes were investigated. These pipes were subjected to mechanical and thermal cyclic stresses due to the internal pressure fluctuations and cooling-heating cycles. Residual stress measurements were carried out for three different depths through the thickness and were correlated to the microstructural observations and microhardness measurements. Results showed that the maximum tensile residual stresses existed at the boundary of weld metal and base metal because of the contraction-expansion effects resulting from phase transformations and cooling rate differences. Fatigue fractures occurred at...