Study On Properties And Structure Of Pd-Ag-(Cu、Cu+Ni) Alloy

Palladium-based alloys have good hydrogen permeation,catalysis,conductivity,corrosion resistance,high temperature and abrasion resistance,which make palladium alloys widely used in the fields of hydrogen purification materials,catalyst materials,electrical contact materials,electroplating materials and dental materials.Alloying of palladium and other metals can greatly enhance its strength,hardness,corrosion resistance and conductivity.In this thesis,palladium and silver,copper,nickel alloying,through a series of cold processing and heat treatment,improve the mechanical and electrical properties of the alloy,expect to get high strength,high hardness,high conductivity and good plasticity of palladium alloy electrical contact material.In this thesis,the changes of mechanical and electrical properties such as hardness,tensile strength,elongation and conductivity of alloys Pd45Ag40Cu15 and Pd45Ag39Cu15Ni1 with different processes,such as solid solution,aging,processing and annealing,were studied,and through metallographic microstructure analysis,XRD analysis,The microstructure of the alloy after different treatment process was analyzed by microscopic analysis of fracture morphology.The results of the study are as follows:1.The solid solution hardening effect of Pd-Ag-（Cu,Cu+Ni）alloy is very obvious,and the solid solution hardness of alloy Pd45Ag40Cu15 and Pd45Ag39Cu15Ni1 is increased by 52%and 62%respectively compared with the hardness of each alloy.Compared with the alloy of the two components,the effect of Pd45Ag39Cu15Ni1 solid solution strengthening is better.2.Pd-Ag-（Cu,Cu+Ni）alloy aging effect is also very significant,the hardness,tensile strength and conductivity are enhanced after aging,alloy aging treatment,the change of temperature than prolonged heat preservation time on the effect of aging hardening.Alloy in 450℃insulation 1h has the best aging effect,compared with solid solution hardness,alloy Pd45Ag40Cu15 hardness increased by 112%,and alloy Pd45Ag39Cu15Ni1 hardness increased by 66%.The aging effect of the alloy Pd45Ag39Cu15Ni1 is lower than that of Pd45Ag40Cu15,and the tensile strength and elongation rate of the aging Pd45Ag39Cu15Ni1 are all decreased.3.The tensile strength and hardness of Pd-Ag-（Cu,Cu+Ni）alloys after processing increase significantly,but the electrical conductivity does not change significantly.And the difference in the degree of deformation of the alloy pre-processing will affect the work hardening results of the alloy,the greater the degree of pre-deformation,the higher the hardness of the alloy after processing.When the deformation is 90%,the hardness of the alloy Pd45Ag40Cu15 with 30%,50%,and 80%pre-deformation and the Pd45Ag39Cu15Ni1 with 80%pre-deformation reaches 300HV_0.2,336HV_0.2,339HV_0.2and 345HV_0.2,respectively,compared with the respective solid solution states,the increase rates were 109%,134%,131%and 92%,respectively.The alloy Pd45Ag39Cu15Ni1 has higher work hardening results,but increase rates is not as good as Pd45Ag40Cu15.4.Alloy Pd-Ag-（Cu,Cu+Ni）annealing,the effect of aging hardening,alloy tensile strength,hardness and conductivity are first increased and then decreased.The strength,hardness and conductivity of 90%deformed alloy Pd-Ag-（Cu,Cu+Ni）were maximum when annealed at 350℃,400℃and 450℃respectively.At this time,the hardness of alloy Pd45Ag40Cu15 is 394HV_0.2,tensile strength is 1197.5MPa,conductivity is6.29x10⁶s/m,Alloy Pd45Ag39Cu15Ni1 hardness is 371HV_0.2,tensile strength is1264.4MPa,The conductivity is 4.37x10⁶s/m.The mechanical and electrical properties of composite alloy,such as hardness,strength,conductivity and plasticity,are Pd-Ag-（Cu,Cu+Ni）alloy by 80%pre-deformation processing-Solution treatment-90%processing deformation-450℃*1h annealing treatment can obtain the best comprehensive performance.5.After adding Ni element to the alloy,the biggest change is that the original single solid solution becomes two homogeneous solid solution,and when the alloy Pd45Ag39Cu15Ni1 is treated with low temperature,one of the solid solution will change into a brittle phase,and the large deformation will restrain the transformation of the phase,so the strength of the alloy at this time is extremely high,and the plasticity is also better.