Friction stir welding（FSW） is a solid-state welding process which is capable of joining materials which are relatively difficult to be welded by fusion welding process. Further, this process is highly energy-efficie...Friction stir welding（FSW） is a solid-state welding process which is capable of joining materials which are relatively difficult to be welded by fusion welding process. Further, this process is highly energy-efficient and environmental-friendly as compared to the fusion welding. Despite several advantages of FSW over fusion welding, the thermal cycles involved in FSW cause softening in joints generally in heat-treatable aluminum alloys（AAs） due to the dissolution or coarsening of the strengthening precipitates leading to decrease in mechanical properties. Underwater friction stir welding（UFSW） can be a process of choice to overcome these limitations. This process is suitable for alloys that are sensitive to heating during the welding and is widely used for heat-treatable AAs. The purpose of this article is to provide comprehensive literature review on current status and development of UFSW and its importance in comparison to FSW with an aim to discuss and summarize different aspects of UFSW. Specific attention is given to basic principle including material flow, temperature generation, process parameters, microstructure and mechanical properties. From the review, it is concluded that UFSW is an improved method compared with FSW for improving joint strength. Academicians, researchers and practitioners would be benefitted from this article as it compiles significantly important knowledge pertaining to UFSW.展开更多
Underwater friction stir processing was performed on commercially pure copper with a purity of 99.8% and a copper-zinc alloy(brass). The tool was made of tungsten carbide in the threaded cone form. Friction stir proce...Underwater friction stir processing was performed on commercially pure copper with a purity of 99.8% and a copper-zinc alloy(brass). The tool was made of tungsten carbide in the threaded cone form. Friction stir processing was performed at a tool rotational speed of 1800 r/min and a tool transverse speed of 4 mm/min while the samples were immersed in a water tank with a water circulation system. In order to evaluate the effect of the number of process passes on the microstructure and mechanical properties of the samples, this process was continued for up to 6 passes. Microscopic studies using light microscopy on commercially pure copper samples show significant decrease in grain size. Likewise, the hardness of the cross-sectional area shows an increase more than the base metal. The X-ray diffraction pattern of the underwater friction stir processed samples in comparison to that of the base metal exhibits shorter and wider peaks, while the background of the pattern is increased. The sum of these factors represents the formation of an amorphous/ultrafine grained structure. Also, the wear behavior of the samples was investigated by means of pin-on-disk method and the results show that the friction coefficient of processed samples is decreased compared to that of the base metal. The results of wear and hardness tests show that the underwater friction stir processing can significantly improve the wear resistance and hardness of commercially pure copper and brass.展开更多
The purpose of this study is to reveal the microstructure and mechanical properties of friction stir welding(FSW)joints prepared in water/air.For comparable analysis,the submerged FSW(SFSW)and conventional FSW are bot...The purpose of this study is to reveal the microstructure and mechanical properties of friction stir welding(FSW)joints prepared in water/air.For comparable analysis,the submerged FSW(SFSW)and conventional FSW are both conducted on 6061-T6 aluminum alloy plates at the combination rotation speed of 800 r/min and the traverse rate of 50 mm/min.The results show that a greatest grain refinement is achieved by SFSW,which is remarkably smaller than that of the base material(BM)and air FSW(AFSW)samples,leading to a significant improvement of tensile strength from 202.5 MPa in the AFSW sample to 232 MPa in the SFSW sample.展开更多
文摘Friction stir welding（FSW） is a solid-state welding process which is capable of joining materials which are relatively difficult to be welded by fusion welding process. Further, this process is highly energy-efficient and environmental-friendly as compared to the fusion welding. Despite several advantages of FSW over fusion welding, the thermal cycles involved in FSW cause softening in joints generally in heat-treatable aluminum alloys（AAs） due to the dissolution or coarsening of the strengthening precipitates leading to decrease in mechanical properties. Underwater friction stir welding（UFSW） can be a process of choice to overcome these limitations. This process is suitable for alloys that are sensitive to heating during the welding and is widely used for heat-treatable AAs. The purpose of this article is to provide comprehensive literature review on current status and development of UFSW and its importance in comparison to FSW with an aim to discuss and summarize different aspects of UFSW. Specific attention is given to basic principle including material flow, temperature generation, process parameters, microstructure and mechanical properties. From the review, it is concluded that UFSW is an improved method compared with FSW for improving joint strength. Academicians, researchers and practitioners would be benefitted from this article as it compiles significantly important knowledge pertaining to UFSW.
文摘Underwater friction stir processing was performed on commercially pure copper with a purity of 99.8% and a copper-zinc alloy(brass). The tool was made of tungsten carbide in the threaded cone form. Friction stir processing was performed at a tool rotational speed of 1800 r/min and a tool transverse speed of 4 mm/min while the samples were immersed in a water tank with a water circulation system. In order to evaluate the effect of the number of process passes on the microstructure and mechanical properties of the samples, this process was continued for up to 6 passes. Microscopic studies using light microscopy on commercially pure copper samples show significant decrease in grain size. Likewise, the hardness of the cross-sectional area shows an increase more than the base metal. The X-ray diffraction pattern of the underwater friction stir processed samples in comparison to that of the base metal exhibits shorter and wider peaks, while the background of the pattern is increased. The sum of these factors represents the formation of an amorphous/ultrafine grained structure. Also, the wear behavior of the samples was investigated by means of pin-on-disk method and the results show that the friction coefficient of processed samples is decreased compared to that of the base metal. The results of wear and hardness tests show that the underwater friction stir processing can significantly improve the wear resistance and hardness of commercially pure copper and brass.
文摘The purpose of this study is to reveal the microstructure and mechanical properties of friction stir welding(FSW)joints prepared in water/air.For comparable analysis,the submerged FSW(SFSW)and conventional FSW are both conducted on 6061-T6 aluminum alloy plates at the combination rotation speed of 800 r/min and the traverse rate of 50 mm/min.The results show that a greatest grain refinement is achieved by SFSW,which is remarkably smaller than that of the base material(BM)and air FSW(AFSW)samples,leading to a significant improvement of tensile strength from 202.5 MPa in the AFSW sample to 232 MPa in the SFSW sample.
