Evaluation of the mechanical properties of friction stir lap welded joints for dissimilar aluminum alloys(AA1100 To AA6061)
In this study friction stir lap welding (FSLW) joints are made for similar and dissimilar aluminum alloys (AA1100 to AA6061-T6) sheets of 3mm thickness by varying the welding parameters, such as tool rotation speeds (1000, 1250 & 1600 rpm) and welding speeds (35, 75 & 100 mm/min) and pin length of (2.8, 5.4 & 5.7mm) with using cylindrical threaded tool pin profile. Many tests and inspections were performed such as X-Ray radiographic and tensile shear test to evaluate the weld quality and joint efficiency under different welding parameters. Microhardness and microstructure observations were carried out at the best welding parameters. The maximum tensile shear force (4.93 KN) and joint efficiency (93%) were obtained when welding process was conducted by a new technique with using friction stir diffusion welding process at the welding speed of 75 mm/min, tool rotation speed of 1250 rpm and using pin length of 2.8 mm. It was found that the Vickers hardness of the similar and dissimilar joints reached to the maximum value at stir zone and drop toward the base metals.
A Study of Diffusion Phenomenon in Friction Stir Lap Welding Joints for Low Carbon Steel C10 to Aluminum Alloy AA1100-H112
In this study the friction stir lap welding was carried out by a new technique (diffusion bonding phenomenon) between (AA1100 and low carbon steel C10 sheets of 3mm and 1mm thickness respectively. These alloys have difference ranges in melting temperature and other physical properties.  Different parameters were used: tool rotation speeds (630, 1250) rpm, travel speeds (80, 32) mm/min. and pin length (2.8,3) mm  using cylindrical threaded pin. Many tests and inspections were performed such as tensile shear test and X-Ray diffraction tests. Microhardness and microstructure observations were conducted by using optical and SEM. The above tests were used to evaluate the weld quality and joint efficiency under different welding parameters. Best result for  FSLW by  diffusion phenomenon  appear in (low carbon steelC10 / AA1100-H112) joint at 1250rpm  in 32 mm/min. with 2.8mm pin length and the maximum tensile shear strength was (3.9)KN.It was found that the highest micro hardness was (138HV) at the interface between the low carbon steel and AA1100.
Cyclic strain induced precipitation in a solution treated aluminium alloy
Abstract Cyclic mechanical tests were carried out on specimens of an Al-Mg-Si alloy, 6351, in the solution treated condition and the behaviour compared to that of an Al-Mg alloy, 5182. Both showed marked cyclic hardening typical of non precipitation hardened aluminium alloys. In the 5182 alloy, this hardening has been attributed to dislocation pinning by solute atoms. Differences in mechanical behaviour were observed which suggested that hardening of the 6351 alloy may be due to a cyclic strain induced precipitation hardening effect rather than solute atom pinning. Using a previously described weak beam technique, evidence was found for precipitate formation on dislocations in the cycled 6351 alloy. The evolution of the microstructure during cycling was different in the two alloys. In the 6351 alloy, the dislocation density reached a maximum and then decreased with further cycling even though hardening continued to occur. This was attributed to progressive deactivation of dislocation sources whilst normal annihilation reactions continued to occur among the mobile dislocations.