Journal of Welding Science

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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.
 

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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

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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 .

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