Investigations On Aging And Hot Deformation Behaviors Of Cu-Ni-Si-Co Alloy

Due to the high performance such as excellent strength,conductivity,good mechanical and physical properties,Cu-Ni-Si alloy is an important basic material for lead frame,resistance welding electrode and nuclear reactor wall.A new type of CuNi-Si alloy can be developed according to combine with the addition of trace elements and aging treatment to meet the industrial demands.In this experiment,three kinds of alloys,Cu-1.5Ni-1.0Co-0.6Si,Cu-1.5Ni-1.5Co-0.6Si,and Cu-1.5Ni-1.5Co-0.6Si-0.15 Ce alloy are designed and prepared by vacuum melting.The aging behaviors of the three kinds of alloys with different cold deformation after solution are studied.The microstructure and aging process of the alloy are analyzed.The changes of electrical conductivity and microhardness of the alloy are described.The equations of electrical conductivity and aging precipitation kinetics are established.The aging strengthening mechanism and aging precipitation kinetics of the alloy are discussed.The hot deformation behavior of the alloy deform on gleeble-1500 d thermal simulator with the strain temperature 700-900 ?,and the strain rate 0.001-10 s-1.The true stress-true strain curves of the alloy under different hot deformation conditions are drawn.The relationship between the strain temperatures,strain rates and flow stress are analyzed.The constitutive model of CuNi-Co-Si alloy is constructed.The hot working maps of the alloy is drawn and the deformation mechanism was analyzed.The results show that the conductivity and hardness of Cu-Ni-Co-Si alloy can be improved by cold deformation before aging.At the same aging time,the higher the aging temperature,the higher conductivity and hardness.The mass fraction of the alloying element Co increase from 1.0wt.% to 1.5wt.%,the conductivtiy decrease.There are three types of precipitates in Cu-Ni-Co-Si alloy:(Ni,Co)2Si,?-Ni3 Si and massive Co2 Si after aging treatment.The(Ni,Co)2Si phase formed by the substitution of some Ni atoms by Co atoms grows with the increase of Co content from 1.0wt.% to 1.5wt.%.A definite phase relationship between(Ni,Co)2Si and ?-Ni3 Si and copper matrix in Cu-Ni-Co-Si alloy aged at 450 ? for 2 h can be obtained as(220)_Cu //(011)_?//(100)_p;[001]_m//[001] _?//[100]_p,(220)_Cu //(011)_?//(100)_p';[001]_m//[001]_?//[100]_p',(111-)_Cu //(111)_?//(021)_p;[112]_m//[112]_?//[012]_p.In the hot deformation process,Cu-Ni-Co-Si alloy is a temperature and strain rate sensitive alloy.The stress value of the alloy increases with the increase of temperature and increases with the decrease of strain rate.When the content of Co element in the alloy increase from 1.0wt.%.to 1.5wt.%.,the flow stress of the alloy increase obviously in the process of hot deformation.When the content of Co increase from 1.0wt.%.to 1.5wt.%.,the activation energy of hot deformation decrease by 16%.The addition of Ce increase the hot deformation activation energy by 56%.The rare earth elements can expand the thermal processing stability region of the alloy and increase the hot working behavior.