The present work pertains to the study on joining of AA6061 and AISI 4340 through continuous drive friction welding. The welds were evaluated by metallographic examination, X-ray diffraction, electron probe microanaly...The present work pertains to the study on joining of AA6061 and AISI 4340 through continuous drive friction welding. The welds were evaluated by metallographic examination, X-ray diffraction, electron probe microanalysis, tensile test and microhardness. The study reveals that the presence of an intermetallic compound layer at the bonded interface exhibits poor tensile strength and elongation. Mg in AA6061 near to the interface is found to be favourable for the formation and growth of Fe2Al5 intermetallics. Introduction of silver as an interlayer through electroplating on AISI 4340 resulted in accumulation of Si at weld interface, replacing Mg at AA6061 side, thereby reducing the width of intermetallic compound layer and correspondingly increasing the tensile strength. Presence of silver at the interface results in partial replacement of Fe-Al based intermetallic compounds with Ag-Al based compounds. The presence of these intermetallics was confirmed by X-ray diffraction technique. Since Ag-Al phases are ductile in nature, tensile strength is not deteriorated and the silicon segregation at weld interface on AA6061 in the joints with silver interlayer acts as diffusion barrier for Fe and further avoids formation of Fe-Al based intermetallics. A maximum tensile strength of 240 MPa along with 4.9% elongation was obtained for the silver interlayer dissimilar metal welds. The observed trends in tensile properties and hardness were explained in relation to the microstructure.展开更多
Textile-reinforced concrete(TRC)is suitable to repair and reinforce concrete structures in harsh environments.The performance of the interface between TRC and existing concrete is an important factor in determining th...Textile-reinforced concrete(TRC)is suitable to repair and reinforce concrete structures in harsh environments.The performance of the interface between TRC and existing concrete is an important factor in determining the strengthening effect of TRC.In this paper,a double-sided shear test was performed to investigate the effects of the chloride dry-wet cycles on the average shear strength and slip at the interface between the TRC and existing concrete,also considering the existing concrete strength,bond length,textile layer and short-cut fiber arrangements.In addition,X-ray diffraction(XRD)technology was used to analyze the microscopic matter at the interface in the corrosive environment.The experimental results indicate that the interface performance between TRC and existing concrete would decrease with continued chloride dry-wet cycles.Compared with the specimen with a single layer of textile reinforcement,the specimens with two layers of textile with added PVA or AR-glass short-cut fibers could further improve the properties of the interface between the TRC layer and existing concrete.For the TRC with a single layer of textile,the average shear strength tended to decrease with increasing bond length.In addition,the strength grade of the existing concrete had a minor effect on the interface properties.展开更多
基金Defence Research and Development Organization for the financial support
文摘The present work pertains to the study on joining of AA6061 and AISI 4340 through continuous drive friction welding. The welds were evaluated by metallographic examination, X-ray diffraction, electron probe microanalysis, tensile test and microhardness. The study reveals that the presence of an intermetallic compound layer at the bonded interface exhibits poor tensile strength and elongation. Mg in AA6061 near to the interface is found to be favourable for the formation and growth of Fe2Al5 intermetallics. Introduction of silver as an interlayer through electroplating on AISI 4340 resulted in accumulation of Si at weld interface, replacing Mg at AA6061 side, thereby reducing the width of intermetallic compound layer and correspondingly increasing the tensile strength. Presence of silver at the interface results in partial replacement of Fe-Al based intermetallic compounds with Ag-Al based compounds. The presence of these intermetallics was confirmed by X-ray diffraction technique. Since Ag-Al phases are ductile in nature, tensile strength is not deteriorated and the silicon segregation at weld interface on AA6061 in the joints with silver interlayer acts as diffusion barrier for Fe and further avoids formation of Fe-Al based intermetallics. A maximum tensile strength of 240 MPa along with 4.9% elongation was obtained for the silver interlayer dissimilar metal welds. The observed trends in tensile properties and hardness were explained in relation to the microstructure.
基金Project(2017XKZD09)supported by the Fundamental Research Funds for the Central Universities,China。
文摘Textile-reinforced concrete(TRC)is suitable to repair and reinforce concrete structures in harsh environments.The performance of the interface between TRC and existing concrete is an important factor in determining the strengthening effect of TRC.In this paper,a double-sided shear test was performed to investigate the effects of the chloride dry-wet cycles on the average shear strength and slip at the interface between the TRC and existing concrete,also considering the existing concrete strength,bond length,textile layer and short-cut fiber arrangements.In addition,X-ray diffraction(XRD)technology was used to analyze the microscopic matter at the interface in the corrosive environment.The experimental results indicate that the interface performance between TRC and existing concrete would decrease with continued chloride dry-wet cycles.Compared with the specimen with a single layer of textile reinforcement,the specimens with two layers of textile with added PVA or AR-glass short-cut fibers could further improve the properties of the interface between the TRC layer and existing concrete.For the TRC with a single layer of textile,the average shear strength tended to decrease with increasing bond length.In addition,the strength grade of the existing concrete had a minor effect on the interface properties.
