In this study, the effects of tool rotational speed, tool traverse speed, and Zn content on the grain size and hardness of the friction-stir-welded （FSWed） Cu-Zn alloy joints were investigated. The microstructures o...In this study, the effects of tool rotational speed, tool traverse speed, and Zn content on the grain size and hardness of the friction-stir-welded （FSWed） Cu-Zn alloy joints were investigated. The microstructures of the joints were examined using optical microscope （OM） and scanning transmission electron microscope （STEM）. Vickers hardness test was conducted to evaluate the hardness of the joints. In addition, the relationships between the process parameters, grain size, and hardness of the joints were established. The results show that the developed relationships predict the grain size and hardness of the joints accurately. The Zn content of the alloys is the most effective parameter on the grain size and hardness, where the tool traverse speed has the minimum effect. The relationship between the hardness and grain size of the joints has a deviation from the Hall-Petch equation due to formation of high dislocation density inside the grains. At higher Zn amounts, the dislocation tangles with high density form instead of dislocation cells, and hence, lower conformity with the Hall-Petch relationship is observed.展开更多
Friction stir welding （FSW） process has gained attention in recent years because of its advantages over the conventional fusion welding process. These advantages include the absence of heat formation in the affected...Friction stir welding （FSW） process has gained attention in recent years because of its advantages over the conventional fusion welding process. These advantages include the absence of heat formation in the affected zone and the absence of large distortion, porosity, oxidation, and cracking. Experimental investigations are necessary to understand the physical behavior that causes the high tensile strength of welded joints of different metals and alloys. Existing literature indicates that tensile properties exhibit strong dependence on the rotational speed, traverse speed, and axial force of the tool that was used. Therefore, this study introduces the experimental procedure for measuring tensile properties, namely, ultimate tensile strength （UTS） and tensile elongation of the welded AA 7020 A1 alloy. Experimental findings suggest that a welded part with high UTS can be achieved at a lower heat input compared with the high heat input condition. A numerical approach based on genetic programming is employed to produce the functional relationships between tensile properties and the three inputs （rotational speed, traverse speed, and axial force） of the FSW process. The formulated models were validated based on the experimental data, using the statistical metrics. The effect of the three inputs on the tensile properties was investigated using 2D and 3D analyses. A high UTS was achieved, including a rotational speed of 1050 r/min and traverse speed of 95 mm/min. The results also indicate that 8 kN axial force should be set prior to the FSW process.展开更多
This investigation was undertaken to predict the mass gain （MG） of cobalt electroless deposition （ED） on ceramic SiC particles.Response surface methodology （RSM） based on a full factorial design with three ED pa...This investigation was undertaken to predict the mass gain （MG） of cobalt electroless deposition （ED） on ceramic SiC particles.Response surface methodology （RSM） based on a full factorial design with three ED parameters and 30 runs was used to conduct the experiments and to establish a mathematical model by means of Design-Expert software.Three ED parameters considered were pH,bath temperature and ceramic particle morphology.Analysis of variance was applied to validate the predicted model.The results of confirmation analysis by scanning electron microscopy （SEM） show that the developed models are reasonably accurate.The pH is the most effective parameter for the MG.Also,the highest mass gain is obtained for the lowest pH,highest bath temperatures and heat-treated SiC particles.In addition,the developed model shows that the optimal parameters to get a maximum value of mass gain are pH,bath temperature and ceramic particle state of 8,70 ℃ and heat treatment,respectively.展开更多
文摘In this study, the effects of tool rotational speed, tool traverse speed, and Zn content on the grain size and hardness of the friction-stir-welded （FSWed） Cu-Zn alloy joints were investigated. The microstructures of the joints were examined using optical microscope （OM） and scanning transmission electron microscope （STEM）. Vickers hardness test was conducted to evaluate the hardness of the joints. In addition, the relationships between the process parameters, grain size, and hardness of the joints were established. The results show that the developed relationships predict the grain size and hardness of the joints accurately. The Zn content of the alloys is the most effective parameter on the grain size and hardness, where the tool traverse speed has the minimum effect. The relationship between the hardness and grain size of the joints has a deviation from the Hall-Petch equation due to formation of high dislocation density inside the grains. At higher Zn amounts, the dislocation tangles with high density form instead of dislocation cells, and hence, lower conformity with the Hall-Petch relationship is observed.
文摘Friction stir welding （FSW） process has gained attention in recent years because of its advantages over the conventional fusion welding process. These advantages include the absence of heat formation in the affected zone and the absence of large distortion, porosity, oxidation, and cracking. Experimental investigations are necessary to understand the physical behavior that causes the high tensile strength of welded joints of different metals and alloys. Existing literature indicates that tensile properties exhibit strong dependence on the rotational speed, traverse speed, and axial force of the tool that was used. Therefore, this study introduces the experimental procedure for measuring tensile properties, namely, ultimate tensile strength （UTS） and tensile elongation of the welded AA 7020 A1 alloy. Experimental findings suggest that a welded part with high UTS can be achieved at a lower heat input compared with the high heat input condition. A numerical approach based on genetic programming is employed to produce the functional relationships between tensile properties and the three inputs （rotational speed, traverse speed, and axial force） of the FSW process. The formulated models were validated based on the experimental data, using the statistical metrics. The effect of the three inputs on the tensile properties was investigated using 2D and 3D analyses. A high UTS was achieved, including a rotational speed of 1050 r/min and traverse speed of 95 mm/min. The results also indicate that 8 kN axial force should be set prior to the FSW process.
文摘This investigation was undertaken to predict the mass gain （MG） of cobalt electroless deposition （ED） on ceramic SiC particles.Response surface methodology （RSM） based on a full factorial design with three ED parameters and 30 runs was used to conduct the experiments and to establish a mathematical model by means of Design-Expert software.Three ED parameters considered were pH,bath temperature and ceramic particle morphology.Analysis of variance was applied to validate the predicted model.The results of confirmation analysis by scanning electron microscopy （SEM） show that the developed models are reasonably accurate.The pH is the most effective parameter for the MG.Also,the highest mass gain is obtained for the lowest pH,highest bath temperatures and heat-treated SiC particles.In addition,the developed model shows that the optimal parameters to get a maximum value of mass gain are pH,bath temperature and ceramic particle state of 8,70 ℃ and heat treatment,respectively.
