The semi-solid-metal 6063 aluminum alloy was developed for the automotive industry. The objective of this research was to optimize parameters in friction stir welding process that can provide the highest tensile strength. The ANOVA factorial design was used to analyze rotation speed, welding speed, and tool geometry at different factor levels of experimentation. The results showed that the optimized tensile strength was 120.7 MPa from the cylindrical tool, rotation speed was from 1300 to 2100 rpm, and welding speed less than 75 mm/min in the coefficient of determination R2 was 95.09%, as can be considered from the regression equation. The examination of the stir-zone and thermal mechanical affected zone using SEM and EDX showed that the new recrystallization of the microstructure causes fine grain in the stir-zone, coarse grain in advancing-side thermal mechanical affected zone, and equiaxed grain in the retracting-side thermal-mechanical affect zone. The intermetallic compounds of β-Al5FeSi phase transformation phase were formed to three types, i.e., β″-Al5Fe, Mg2Si, and Al8Fe2Si phase were observed. Moreover, in the stir-zone and thermal-mechanical-affected zone, defects were found such as flash defects, void or cavity defects, crack defects, lack of penetration defects, tunnel defects, kissing bond defects, and dendrite formation defects affecting weldability.
Abstract. The objective of research to investigate the parameters, microstructure and mechanical properties of butt joint SSM356 with SSM6061 aluminum alloy by using RFW processes. The main parameters such as rotation speeds are 1550, 1700 and 1850 rpm, burn-off length are 2, 2.5 and 3 mm respectively. For experiment found that, both materials have weld ability to get along well though it has a different chemical composition, the changes in welded metals microstructures occurs deformation leads to smaller particle size. The average dimensions of Mg2Si particles were measured at 0.998 µm long and 1.021 µm wide when one of the workpiece was rotated at 1850 rpm with 2.5 mm burn-off length. The maximum average tensile strength is 87.24 MPa, efficiency of the weld joints is 51.89 percent compared with the base metal of SSM356 aluminum alloys, (base metal is 168.12 MPa) and efficiency of the weld joints is 68.45 percent compared with the base metal of SSM6061 aluminum alloys (base metal is 127.44 MPa). Furthermore, small particles distributed in the weld metal promotes increasing hardness property up to 65.56 HV in the weld metal as compared with those of the base metals.
This research aims to study the influence of parameters that affect the mechanical properties of semi-solid-metal 7075 aluminum alloy with friction stir spot welding process. The parameters for this experiment such as rotation welding speed at 380, 760, 1240 and 2500 rpm and welding time at 60, 90 and 120 seconds were employed respectively. The study found that the welded specimens at all the conditions can be welded very well. Moreover, friction stir spot welding process showed that the hardness in weld zone had an average value at 79.83 HV which is lower than the hardness of the base metal. The shear tensile strength of the welded specimens had the average value approximately 194.20 MPa at rotation welding speed of 2500 rpm, welding time of 90 seconds and plunge of depth of 2 millimetres. The microstructure in the weld zone and thermal mechanical affected zone were deformed permanently. Therefore, friction stir spot welding process of this aluminum alloy provided good effects on mechanical properties. Statistical analysis showed that the coefficient of determination R-square was equal to 93.50 percent. This means that the variations of the experiments were controllable, such as equipment or other factors in the experiment. For the remaining, only 6.50 percent was uncontrolled factors.
SSM 356 aluminum alloys was obtained from a rheocasting technique named gas induced semi solid process has globular structure on base. The friction welding method conserve microstructure that is similar to the original structure of the base material a globular structure. It is also found that a rotational speed of 1750 RPM, burn of Length of 3.2 millimeters and welding time (upset time) of 30 second can produce a very good weld. The results of the investigation have shown that a have average hardness in the range 58.13 HV.
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