Microstructure evolution and property analysis of Mg1/Al1060 vacuum diffusion welded joints
The reaction of industrial pure magnesium Mg1 and industrial pure aluminum Al1060 was realized by using va-cuum diffusion welding technology.Scanning electron micro-scope,energy spectrometer,universal mechanical testing ma-chine,microhardness tester and electrochemical workstation were used to study the microstructure,physical composition and properties of diffusion bonding layer.The results show that Mg/Al vacuum diffusion welding generated a diffusion re-action layer composed of magnesium-aluminum intermetallic compounds at the joint,and with the prolongation of the hold-ing time,the thickness of the reaction layer gradually increases,and the microstructure morphology undergoes obvious changes.At the initial stage of diffusion,the reaction layer shows a monolayer structure,and the Mg2Al3 phase precipit-ates preferentially at the joint interface;when the holding time reaches 60 min,the interface generates a new phase layer of Mg17Al12;when the holding time is extended to 90 min,the re-action layer evolves into a three-layer structure consisting of a Mg2Al3 layer,a Mg17Al12 layer,and a(Mg17Al12 + Mg-based solid solution)layer.With the prolongation of the holding time,the shear strength of the joint showed a tendency of in-creasing and then decreasing,and the shear force that could be withstood during the holding time of 60 min reached 1 245.7 N,and the fracture occurred at the Mg2Al3 reaction layer near the aluminum side.The microhardness of each welded layer was significantly higher than that of the magnesium and alu-minum base material,and the Mg2Al3 layer exhibited the highest microhardness of 320.6 HV.The corrosion current density of the Mg1 layer was the smallest,2.199×10-3 A/cm2,while the corrosion current density of the Al1060 layer,the Mg2Al3 layer,the Mg17Al12 layer,and the(Mg17Al12 + Mg based solid solution)layer increased by one order of mag-nitude.The order of corrosion rate is Mg1>(Mg17Al12 + Mg based solid solution)>Mg2Al3>Mg17Al12>Al1060.
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