| Skutterudite thermoelectric materials have high conversion efficiency,great mechanical properties,and economical practicability in the medium temperature range(500-550?).They have achieved good applications in the field of deep-space exploration and the field of automobile exhaust waste heat recovery.Large-scale use puts forward higher requirements on the reliability of device joints.The skutterudite needs to be connected with electrodes to form a thermoelectric power generation device during application.The contact effect,element diffusion,and thermal expansion coefficient matching problems need to be considered during the connection process.Therefore,it is urgent to develop a connection intermediate layer that can effectively solve the above problems at the same time.In this paper,the FeCoNiCrMo high-entropy alloy intermediate layer is designed and prepared,and the diffusion welding process of the CuMo alloy electrode and the p-type Ce0.8Fe3CoSb12 skutterudite thermoelectric material is studied.The high-temperature thermal stability of the joint and the service time are further explored.The law of influence on its contact resistivity.First,the diffusion welding connection of two high-entropy alloy intermediate layers FeCoNiCrX(X=Cu,Mo)and Ce0.8Fe3CoSb12 skutterudite was initially explored,and the weldability of the two intermediate layers was studied by observing the microstructure characteristics of the connection interface.The results show that when the FeCoNiCrCu high-entropy alloy is connected with skutterudite by diffusion welding,the mutual diffusion of Cu and Sb elements is serious,and there are longitudinal and transverse through cracks in the joint,and the thermal expansion coefficients of the two are quite different;while FeCoNiCrMo high-entropy alloy and skutterudite The joint interface of the mine is well bonded.The CuMo alloy electrode and p-type Ce0.8Fe3CoSb12 skutterudite thermoelectric material are diffusion-connected with the FeCoNiCrMo high-entropy alloy intermediate layer.The interfaces of the connection joints are complete,straight,and defect-free.The typical interface structure is CuMo/(Ni,Cu)ss/FeCoNiCrMo/Mo3Sb7/(Fe,Co,Ni,Cr)Sb/p-type skutterudite.The influence of welding temperature,welding pressure,and holding time on the micro structure and mechanical properties of the joint was explored.The optimal process parameters are as follows:the welding temperature is 600?,the welding pressure is 40 MPa,and the holding time is 10 min.At this time,the contact resistance of the joint is The rate is 1.8 ??·cm2,the joint shear strength is 21.6 MPa,and the joint shear fracture position appears at the FeCoNiCrMo/p-type skutterudite interface.The CuMo/Ni/FeCoNiCrMo/p-type skutterudite joints were annealed at a service temperature of 550? for 50 h,100 h,and 640 h,respectively.After the joints were annealed for 640 h,the metallurgical bonding at the CuMo/Ni/FeCoNiCrMo interface was still good.The formed(Cu,Ni)ss can further improve the interface strength,the thickness of the reaction layer at the interface of the FeCoNiCrMo/p-type skutterudite joint is 14.4 ?m;the shear strength of the joint is reduced to 18.8 MPa,and the contact resistivity of the joint is increased to 4.2 ??·cm2.By fitting the experimental data of the joint reaction layer thickness and contact resistivity after annealing,it is predicted that the joint reaction layer thickness after annealing at 550? for 100 days(2400 h)will not exceed 25 ?m,and the contact resistivity will not exceed 6.5 ??·cm2;It is predicted that the thickness of the reaction layer of the joint after annealing at 550? for 1 year(8760 h)will not exceed 45 ?m,and the contact resistivity will not exceed 11 ??·cm2. |
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