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
In this paper,the different influences of lanthanum (La) and cerium (Ce) species on the stability of Y zeolite were studied by X-ray diffractometry (XRD),X-ray photoelectron spectroscopy (XPS),and multinuclear (27Al,2...In this paper,the different influences of lanthanum (La) and cerium (Ce) species on the stability of Y zeolite were studied by X-ray diffractometry (XRD),X-ray photoelectron spectroscopy (XPS),and multinuclear (27Al,29Si) solidstate nuclear magnetic resonance spectroscopy (NMR).It was found that the stability of Y zeolite could be enhanced by the introduction of La or Ce species;however,the former effect was more remarkable than the latter.These results were also confirmed theoretically by density functional calculations.There was a strong interaction between the rare earth (La or Ce) species and Y zeolite clusters,which restrained the formation of extra-framework aluminum and enhanced evidently the stability of Y zeolite.Furthermore,the interaction between La species and Y zeolite was stronger than that of Ce species with Y zeolite.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the Ministry of Science and Technology of China for providing financial support through the National 973 Project (Grant No. 2006CB202501)
文摘In this paper,the different influences of lanthanum (La) and cerium (Ce) species on the stability of Y zeolite were studied by X-ray diffractometry (XRD),X-ray photoelectron spectroscopy (XPS),and multinuclear (27Al,29Si) solidstate nuclear magnetic resonance spectroscopy (NMR).It was found that the stability of Y zeolite could be enhanced by the introduction of La or Ce species;however,the former effect was more remarkable than the latter.These results were also confirmed theoretically by density functional calculations.There was a strong interaction between the rare earth (La or Ce) species and Y zeolite clusters,which restrained the formation of extra-framework aluminum and enhanced evidently the stability of Y zeolite.Furthermore,the interaction between La species and Y zeolite was stronger than that of Ce species with Y zeolite.
