Preparation And Properties Of Half-Heusler Alloy/Cu Joint

Thermoelectric materials can realize the direct conversion of thermal energy to electrical energy,and use waste heat generated by industry,geothermal or solar thermal energy for thermoelectric power generation,which is an effective way to improve energy utilization and vigorously develop clean energy.At this stage,the ZT values of n-type and p-type Half-Heusler alloy thermoelectric materials have reached above 1.0,but there are still few researches on thermoelectric devices,so the reliable HH/Cu joint connection process is explored for the realization of Half-Hesuler thermoelectric materials device-based applications are of great significance.Based on the high-temperature vacuum brazing process,this paper selects Ag₇₂Cu₂₈ eutectic solder for the connection of HH/Cu joints,and explores the influence of brazing process parameters and annealing time on the interface structure and properties of HH/Cu joints.The study found that brazing process parameters(brazing time,brazing temperature)have an important impact on the interface structure of HH/Cu joints.With the increase of brazing temperature and brazing time,the thickness of the joint's weld seam and the diffusion reaction layer gradually increases,the number of intermetallic compounds at the interface gradually increases.With the extension of the annealing time,the thickness of the diffusion reaction layer at the joint increases,and the number of intermetallic compounds increases,the weld gradually dissolves to the Cu electrode,and the thickness of the weld area gradually decreases.The study pointed out that the brazing temperature and brazing time have similar effects on the mechanical properties of the joints.With the increase of temperature and time,the shear strength first increases and then decreases.The brazing temperature of n-HH/Cu joints is When the brazing temperature is 830?and the brazing time is 10 min,the shear strength is the highest,which is 34.3 MPa.When the brazing temperature of p-HH/Cu joint is 820?and the brazing time is 10 min,the shear strength still reaches 25.7 MPa.Both can meet the service requirements of the joint.Studies have shown that,for n-HH/Cu joints,when the brazing temperature is830?and the brazing time is 10 min,the contact resistivity of the joint is less than1??·cm².For p-HH/Cu joints,when the brazing temperature is 820?and the brazing time is 10 min,the contact resistivity of the joint is less than 1??·cm².Because the elements in the HH alloy seriously diffuse to the electrode side,the annealing stability of the HH/Cu joint is poor,so it needs to be considered adding barrier material between the HH alloy and the Cu electrode to obtain a more reliable Half-Heusler thermoelectric device.