Showing 5 results for Emami
M. Ostovar, T. Saeid, A. Mostafapour, S. Emami,
Volume 4, Issue 2 (Journal OF Welding Science and Technology of Iran 2019)
Abstract
In the TIG-MIG hybrid welding, higher weld efficiency and better weld quality are obtained with respect to each individual TIG and MIG welding methods. Moreover, in this method, the MIG arc is more stable in pure argon shielding gas. Therefore, in this study, the influence of TIG-MIG hybrid welding parameters on the welds appearance quality and welds depth to width ratio of a 316L austenitic stainless steel was investigated using optimum parameters of Taguchi design of experiments (DOE). Microstructure of the heat affected zone (HAZ) obtained from the hybrid welding was compared with those of each individual MIG and TIG welding techniques under equal heat-input condition. The results indicated that the most important parameter in the hybrid method to obtain the best appearance quality and the highest depth to width ratio is the distance between the two arcs. The MIG and TIG currents are the next influencing parameters. The width of HAZ and the size of constituent grains in hybrid welding with optimum parameter, were smaller than those of each individual TIG and MIG processes due to the higher associated cooling rate in the hybrid welding technique.
S. Emami, T. Saeid,
Volume 5, Issue 2 ((Journal OF Welding Science and Technology) 2020)
Abstract
Friction stir welding (FSW) was conducted on AISI 304 austenitic stainless steel plate with 2 mm thickness. The FSW was performed at a welding and rotational speeds of 50 mm/min and 400 rpm, respectively. Microstructure observations by the optical microscopy showed that a severe grain refinement occurred in the stir zone (SZ). Electron backscattered diffraction analysis (EBSD) results indicated that high fraction of low angle grain boundaries (LAGBs) developed in the thermo-mechanically affected zone (TMAZ) through the occurrence of the dynamic recovery. Moreover, in the path from the TMAZ towards the SZ, the fraction of high angle grain boundaries (HAGBs) increased with decreasing the fraction of LAGBs through the occurrence of continuous dynamic recrystallization (CDRX). 100 Pole figure showed the formation of shear texture components of A*1 and A*2 in the SZ which implied the occurrence of CDRX mechanism.
M. Hajizadeh, S. Emami, T. Saeid,
Volume 6, Issue 1 (Journal OF Welding Science and Technology 2020)
Abstract
Friction stir welding was conducted on AISI 304 austenitic stainless steel sheet with dimensions of
100 mm × 100 mm × 2 mm. The FSW was performed at a welding speed of 150 mm/min and rotational speeds of 400 and 800 rpm. The results showed that high frequency of low angle grain boundaries (LAGBs) were formed through dynamic recovery in the thermo-mechanically affected zone (TMAZ). Higher amount of LAGBs were developed in the TMAZ of welded sample with 800 rpm due to the higher amount of strain and heat generated. High fraction of high angle grain boundaries were formed in the stir zone (SZ) of the welded samples through the occurrence of continuous dynamic recrystallization (CDRX). A very fine microstructure developed in the sampled welded with lower rotational speed. Analysis of texture using {111} Pole figures showed the formation of shear texture components in the SZ of both welded samples. The intensity of the obtained texture for the sample welded with 800 rpm was greater. The formation of shear texture components in the SZ of both samples implied the occurrence of CDRX mechanism
S. Emami, T. Saeid,
Volume 6, Issue 1 (Journal OF Welding Science and Technology 2020)
Abstract
Single phase brass strips with 2 mm thickness were severely deformed through 1 and 3 cycles of accumulative roll bonding process (ARB). ARB process effectively increased the hardness, yield strength, and the ultimate strength of the processed materials. The hardness of processed material increased from 95 HV in annealed material to 225 HV in 3 cycle ARBed material, and the yielding and ultimate strengths increased more than 5 and 2 times of the annealed sample, respectively. Friction stir welding (FSW) process was successfully conducted on the annealed and ARBed samples to investigate and compare the microstructure and the mechanical properties of the joints obtained in bead on plate configuration. Microstructural observations showed that very fine dynamically recrystallized grains developed in the stir zones (SZs) of all welded samples. Mechanical properties were evaluated by hardness and tensile testing. Hardness test for the ARBed and FS welded samples showed that the hardness value decreased by 110 Hv in the resultant SZs. Results of tensile testing revealed that yield and ultimate strength of the FS welded ARBed samples 1.3 and 1.8 times are greater than that of the annealed FS welded sample .
M. H. Saebi, A. H. Emami Ghalehghasemi, M. Atapour, A. Saboori,
Volume 11, Issue 2 (Journal OF Welding Science and Technology 2025)
Abstract
The Ti-6242 alloy is of particular significance in additive manufacturing due to its high thermal resistance. However, components fabricated from this alloy using the electron beam powder bed fusion (EB-PBF) process often exhibit poor surface quality, primarily resulting from the layer-by-layer fabrication nature and and the presence of partially melted powder particles. In this study, laser polishing was employed to enhance the surface characteristics of EB-PBF fabricated Ti-6242 specimens using three laser powers (195, 260, and 325 W) and two scanning speeds (4.5 and 3 mm/s). The effects of these parameters on surface roughness, microstructure, and mechanical properties were evaluated through surface profilometry, metallography, hardness, and wear tests. The results indicated that the average surface roughness decreased by up to 93%, from 9.36 µm to 0.61 µm. Moreover, the initial α and β phases transformed into a fine, martensitic α′ phase within the polished layer, leading to a 33% increase in hardness—from 380 to 506 HV—and a significant improvement in wear resistance. Consequently, optimal adjustment of laser polishing parameters can simultaneously reduce surface roughness and enhance the mechanical performance of Ti-6242 components.
