| Cu/Al bimetal not only has high thermal and electrical conductivity of copper,good ductility,but also has aluminum corrosion resistance,cheap and other double excellent performance,widely used in electrical,light industry,machinery manufacturing,construction industry,national defense industry and other fields.Because of the difference of copper aluminum physical and chemical performance,no matter what method can not avoid the Cu/Al interface of intermetallic compound,these compounds have larger hard brittle and poor electrical conductivity,which is causing micro defects such as cracks and rapidly expanding area,and the interface of the thicker IMCs against conductive head mechanics,conductive and corrosion resistance and other properties.This paper is applied to the wet zinc smelting the core component of the cathode plate-Cu/Al conductive head research by vacuum hot pressing system spread Cu/Al bimetal,exploring appropriate combination of process parameters in the vacuum hot pressing diffusion method for the Cu/Al,such as temperature and time,in order to get mechanics,conductive and corrosion resistant performance good Cu/Al conductive head,and explaining the formation process of interface and diffusion mechanism and studying simulation conductive head failure mechanism in the service process.The conclusions are as follows:1.Cu/Al bimetal with good interface was prepared by hot-press diffusion method.The interface phase is generally divided into three layers:Al4Cu9,AlCu and Al2Cu phases.If the holding time and temperature are continuously improved,new phase Al3Cu4 will be generated between Al4Cu9 and AlCu.With the increase of temperature,the rate of atomic diffusion will be accelerated,and with the increase of time,the diffusion distance of atoms will be increased.As Cu/Al transition layer becomes wider and wider,its shear strength gradually decreases,its resistivity becomes larger and larger,and its corrosion resistance weakens.The shear fracture of Cu/Al bimetal occurs between Al matrix and Al2Cu.This is because Al2Cu has a large brittleness and a large gap with the lattice parameters of aluminum matrix.As a result,there are many crystal defects on the connection interface,which is prone to intergranular fracture.2.The formation and growth of Cu/Al bimetallic IMCs can be divided into six stages:physical contact at the interface;IMCs nucleation stage;IMCs grew and connected;Continuous thickening of IMCs and formation stage of new phase;IMCs continuing to thicken and flattening;the IMCs continuing to widen and develop new phases.3.Besides,Miedema was adopted to simulate and calculate the formation enthalpy of the intermetallic compound,and EFH model proved that Al2Cu was formed first.According to the the Arrhenius formula fitting of LnK2-1/T curve,the diffusion activation energy of Total,Al4Cu9,AlCu and Al2Cu are respectively 92.74,106.44,96.03 and 79.81 kJ/mol.The diffusion activation energy of Al2Cu is lower than that of other IMCs,because compared with other cubic or rhombic compounds,Al2Cu belongs to the tetrahedral crystal system.Tetrahedral crystal defects such as dislocation and vacancy are more likely to occur in the crystal structure,and atoms are easier to diffuse at the crystal defects.4.With the increase of corrosion time,the "gully" between aluminum and intermetallic compounds becomes deeper and deeper,the shear strength is extremely reduced,and the conductivity of Cu/Al conductor nods is close to that of aluminum.With the increase of interfacial thickness,the corrosion of Cu/Al conductive head becomes more serious,resulting in the decrease of mechanical properties and conductivity of Cu/Al conductive head.5.Cu/Al conductive head is mainly corroded by copper and aluminum alloy.There are uniform corrosion and crack corrosion in aluminum matrix,and chemical corrosion is the main corrosion on copper side.Because of the electrode potential difference,the intermetallic compound layer also has different degree of alloying. |
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