Control Of Microstructure And Properties Of Cu-(Ni)-Mo Alloys Prepared By Aluminothermic Reaction

Cu alloys are widely used in many fields of modern industry and are one of indispensable non-ferrous materials in human production and life because of their excellent electrical and thermal conductivity conductivity,corrosion resistance and easy processing.However,there is a contradictory relationship between the conductivity and the strength of copper alloys.Therefore,one of the current research focuses is that how to keep the high conductivity and improve the strength of copper alloys.The refractory metal elements W,Mo,Ta and Nb have almost no solid solubility in copper,which can be used as nucleation points to refine grains and raise recrystallization temperature.Meanwhile,the copper alloys with good comprehensive properties are hopeful to be obtained by reasonably controlling the amount of such elements.In this paper,Cu-Mo binary alloys were prepared by aluminothermic reaction method,which has the advantages of simple process,low cost and large alloy size.On this basis,the cluster model of Professor Dong Chuang from Dalian University of technology was introduced to design the alloy composition.The Cu-Ni-Mo ternary alloys with five components were prepared,and then they were rolled at room temperature with 40%,60% and 80% deformation.Finally,the rolled alloys with 80%deformation were treated at 965 °C solution for 1 h and 450 °C aging for 2 h.The structure and properties of the alloys in different states were analyzed in detail:(1)The Cu-Mo binary alloys showed poor formability,existing many macroscopic holes.As the diluent content decreased,the adiabatic temperature increased,the reactant melted fully,the melt fluidity increased,and the formability of as cast alloys improved obviously,but it can not meet the subsequent processing requirements.(2)Based on the cluster model,the as cast Cu-Ni-Mo alloys with different composition have good formability and no macroscopic defects.Namely,on the basis of binary Cu-Mo alloys,the introduction of the third component Ni which can be mutually soluble with Cu,can successfully dispersed the insoluble Mo and significantly improved the fluidity of the melt,thus improved the formability of the alloy.The microstructure of as cast Cu-Ni-Mo alloys consist of equiaxed grains and a small amount of precipitated phases.With the increase of Ni and Mo content,the grain size decreased gradually.The hardness,strength and elongation increased with the increase of Ni and Mo content,while the conductivity decreased gradually,which is mainly caused by lattice distortion caused by more solute atoms solid solution inCu matrix.(3)During the rolling process of the as cast Cu-Ni-Mo alloys,a large number of dislocations and stress concentration are formed inside the alloy,resulting in a large number of lamellar deformation structures,grain refinement,significant increased in strength and hardness,and significant decreased in plasticity.However,there is no obvious change in the phase composition of the alloy.After rolling,the precipitates are broken and distributed more evenly,and the void concentration in the matrix and crystal decreased continuously,which reduced the scattering effect of point defects on electrons,counteracts the increase of resistivity caused by dislocation proliferation,and makes no obvious change in the conductivity of the alloy.(4)After solution and aging treatment,the microstructure of Cu-Ni-Mo alloys changed from rolled fibrous lamellar structure to uniform equiaxed structure,typical annealing twin structure appeared in some grains,the grain size is obviously reduced,the work hardening phenomenon was eliminated,the precipitation phase was partially dissolved,and the precipitation strengthening effect was weakened due to the decreased of precipitation phase.The hardness and strength decreased obviously,while the appearanced of twin structure increased the plasticity of the alloy,which was 6-8 times higher than that of as rolled alloy.Compared with as cast alloy,the strength and plasticity of the alloys have been improved obviously after cold deformation and heat treatment,and the electrical conductivity basically had no loss.The tensile strength of Cu99[Ni12/13Mo1/13]1,Cu97[Ni12/13Mo1/13]3,Cu95[Ni12/13Mo1/13]5,Cu93[Ni12/13Mo1/13]7 and Cu90[Ni12/13Mo1/13]10 alloy are 257.31 MPa,263.56 MPa,305.87 MPa,310.26 MPa and 323.04 MPa,respectively MPa,yield strength are101.53 MPa,105.68 MPa,113.24 MPa,119.45 MPa and 127.12 MPa,elongation are35.61%,41.09%,32.33%,29.68% and 42.04%,electrical conductivity are 42.58%IACS,27.48% IACS,21.25% IACS,15.74% IACS and 12.3% IACS,respectively.