Friction stir welding (FSW) between 3 mm thick AA 5052-O aluminum alloy plates was investigated in the present study. Different welded specimens were produced by employing a constant tool traverse speed of 120 mm/min and by varying... more
Friction stir welding (FSW) between 3 mm thick AA 5052-O aluminum alloy plates was investigated in the present study. Different welded specimens were produced by employing a constant tool traverse speed of 120 mm/min and by varying rotating speeds from 800 to 3000 rpm. The welded joints were characterized by its appearances, microstructural and mechanical properties at room temperature. The measurement of different forces acted on the tool during the FSW of AA 5052-O plates provided a significant insight to determine the quality of the welded joints. From the appearances of the welded joints it was evident that, except the tool rotational speed of 3000 rpm all other rotational speeds produced sound welded joints with smooth surface. The joint produced at 1000 rpm yielded a maximum tensile strength of 132 MPa which was 74% of the base material strength. Field emission scanning electron microscopy (FESEM) and energy dispersive spectroscopy (EDS) analyses on the stir zone suggested that, beta-Mg2Al3 intermetallic phases of the base material were mechanically fractured, smeared and mixed to different geometries due to tool stirring. The dissolution and redistribution of beta-Mg2Al3 second phase particles in the stir zone had a considerable effect on the reduction of the tensile strength of the welded joints. The reduction in hardness at the nugget zone (NZ) of the welded joints under different tool rotational speeds could be attributed to the dislocation of Mg-rich phases and segregation of Mg solute atoms at grain boundaries, which drew solute Mg atoms away from the alpha-aluminum matrix. (C) 2014 Elsevier Ltd. All rights reserved.
In an attempt to develop cadmium-free silver brazing filler metals, the ternary Ag-Cu-In alloys were investigated. The effect of varying indium content on melting temperatures and brazeability of Ag-Cu-In alloys on copper was ascertained... more
In an attempt to develop cadmium-free silver brazing filler metals, the ternary Ag-Cu-In alloys were investigated. The effect of varying indium content on melting temperatures and brazeability of Ag-Cu-In alloys on copper was ascertained in this article. Additionally, microstructures, hardness, and shear strength of the brazed joints were investigated. Investigation of brazeability was carried out using a varying gap test piece method adapted from ISO 5179-1983. With this method, the capillary rise height at different joint gaps was used as a quantitative measure for brazeability. The results from differential thermal analysis showed that with the increase of indium content in Ag-Cu-In, the solidus and liquidus temperatures of the filler metals decreased. However, the increase of indium contents showed no significant improvement to the capillary rise height. The limits of capillary rise height of each filler metal corresponding to the joint gaps of 50 and 100 μm were approximately 45 and 28 mm, respectively. Increasing of indium content led to the increase of an intermetallic phase in the brazed layer which subsequently increased the joint hardness. However, this slightly reduced joint shear strength. The average shear strength of the joint brazed with 60Ag-15Cu-25In filler metal was about 11% lower than that brazed with 60Ag-35Cu-5In filler metal.
