Study On Interface Behavior Between Amorphous Alloy And Copper

The amorphous alloy has unique microstructure,no grain boundary,dislocation and other defects,and exceedingly good physical,chemical and mechanical properties.Still,the application of amorphous alloy in engineering is greatly limited because it is not easy to form at room temperature.Therefore,it is very important to develop a new forming technology in the future application of amorphous alloys.The appearance of the amorphous composite material greatly improves the toughness of the amorphous alloy,and also brings new opportunities for the development of the amorphous alloy.It is the current research hotspot in the field of amorphous materials and welding to effectively expand the application field of the amorphous alloy.In this paper,aiming at the quality of the joint between bulk amorphous alloy and metal,and taking advantage of the difference between the melting properties of amorphous material and metal,pulse laser welding is proposed to realize the welding connection between Zr based amorphous alloy and copper.With the microstructure and properties of the joint as the core and the interface between Zr based amorphous and metal as the breakthrough point,the high quality joint technology and base of amorphous alloy and metal are explored and obtained Undergraduate theory.First of all,the butt fusion welding process of Zr based amorphous alloy(Zr₄₄Ti₁₁Ni₁₀Cu₁₀bBe₂₅)was tested by pulse laser welding,and the well formed butt joint of Zr based amorphous fusion welding was obtained under the a ppropriate process parameters.The joint morphology,crystal phase,crystal structure and thermal stability were analyzed by optical microscopy,XRD,SEM+EDS,Vickers hardness and TG-DSC.The results show that in the secondary electron image of the HAZ,the grain like fine crystal phase is found,while the weld area is small crystal phase;the Bragg diffraction peaks of the HAZ and the fusion area correspond to Zr₂Cu and Zr₂Ni;combined with the crystallization enthalpy of the exothermic peak in the DSC curve,the crystallization fractions of the HAZ and the fusion area are calculated to be4.2%and 32.0%,respectively.Then,pulse laser welding of Zr based amorphous alloy and copper was carried out.The microstructure,chemical composition and mechanical properties of the Zr based amorphous alloy/copper fusion brazing joint were systematically characterized by means of SEM,EDS,XRD,Vickers hardness tester and nanoindentation.The results show that there are crystal peaks in the XRD patterns of HAZ and WZ.In addition,a diffusion layer is formed between the weld zone and the copper.EDS energy spectrum analysis shows that the concentration gradient of elements is formed by the"displacement"mutual diffusion of Cu and Zr formed by the diffusion layer,which indicates that the copper migrates to the weld zone along the WZ/Cu interface during the welding process;the hard intermetallic compounds Zr₂Cu and Zr₂Ni are formed in the weld zone?WZ?and heat affected zone?HAZ?to make the Vickers hard of the joint The degree is slightly higher than that of Zr based amorphous base metal.In the process of nano indentation,the Zr based amorphous base metal with large free volume shows obvious zigzag protrusion,and the weld area with crystal structure shows the highest nano indentation hardness and reduction modulus,while the plastic energy dissipation of Zr based amorphous base metal in nano indentation is the most.Finally,through the calculation of the weld pool and the theory of crystal nucleation and growth,combined with the analysis of the interface mechanism by the finite element simulation,the C curve and the thermal cycle curve related to welding are obtained,and the crystallization kinetics in the weld zone and the heat affected zone is further discussed.In the process of pulsed laser welding,the heat cycle curve of the joint heat affected zone and the weld zone intersects with the continuous heating transition?CHT?curve of the crystallization temperature?T_x?,so that the crystal structure is formed in the weld pool during the solidification process of pulsed laser welding:one is the amorphous solid-phase crystal with short-range atom migration of the solid-phase,and the substrate is used as the seed crystal to gradually extend upward until the crystal surface;the other is the amorphous solid-phase crystal with short-range atom migration of the solid-phase The amorphous exists in the form of a spiral dislocation.Through Scherrer equation and XRD data of Zr based amorphous/Cu,the grain size in different regions of the joint was obtained.