Study On The Anisotropy And Texture Evolution Of Cu-Ni-Si-Mg Alloys For Lead Frames

This research is in intended for making the analysis of reasons for anisotropy effects on alloy sheets caused by solid solution,secondary cold rolling and aging processing,by means of mechanical property tests on Cu-Ni-Si-Mg alloy,in the meantime combining with the determination methods,such as Scanning Electron Microscopy(SEM),Transmission Electron Microscopy(TEM),Optical Microscope(OM),X-ray diffraction(XRD),Energy Dispersive Spectrometer(EDS)and Electron Back-scatter Diffraction(EBSD)to analyze the anisotropy effects and formation rules for Cu-Ni-Si-Mg alloy sheets.Emphasis is laid on the structure and texture changing during first cold rolling,solid solution and secondary cold rolling;In-depth analyses of second phase precipitation and effects on the structure and texture caused by re-dissolution are searched;formation mechanism of anisotropy is revealed;structure optimization of anisotropy and texture controlling technology improvements are put forward;theoretical basis and experimental reference are utilized for comprehensive properties improvements.The conclusions are as follows:(1)With solid solution temperature increase or time extension,In-plane anisotropy of Cu-Ni-Si-Mg alloy sheets is increased in the first place and then tended to be stable;G{011}<100> and Br{011}<211> decreased gradually in terms of texture strength,Cu’{113}<121> and S’{123}<523> increased gradually regarding texture strength;when the solid solution processing reached 850℃/60 s,Rm and Rp0.2 hit the maximum,of which strength-difference will be 103 Mpa and 72MPa;Cu’ and S’ texture strength increase,the quantity of second-phase precipitation and the non-uniform of grains are the main factors for anisotropy.(2)With aging temperature increase,In-plane anisotropy of Cu-Ni-Si-Mg sheets is decreased little by little,while the texture strength of Cu’{113}<121> and S’{123}<523> is increased in the first place and then decreased,however,as aging time prolongs,In-plane anisotropy of Cu-Ni-Si-Mg sheets will be increased and then decreased,and texture strength of Cu’{113}<121> and S’{113}<121> will be decreased little by little.The texture strength of G{011}<100> and Br{011}<211> has been less effected by aging.The decrease of texture strength of Cu’ and S’ is mainly caused by second phase precipitation,in addition,the more the second phase precipitates,the lower of the Cu’ and S’ texture strength value.Second phasecoarsening has no obvious influence on Cu’ and S’ texture strength.(3)In-plane anisotropy of Cu-Ni-Si-Mg sheets will be decreased in the first place and then increased as the secondary cold rolling deformation increase after solid solution;the texture strength of Cu{112}<111>,S{123}<634> and Br{011}<211> will be decreased little by little and that of G{011}<100> will be increased.Cold rolling deformation of 30%~45%after solid solution,the strength-difference between Rm and Rp0.2 will be 21 MPa and 25 MPa,the material would be isotropic.(4)Cu-Ni-Si-Mg falls into the category of low level fault energy metals.various orientations of grains will flow to {011}<211> during the first cold rolling process,The crystal nucleus with {113}<121> and {123}<523> orientation showed obvious growth advantage in the process of solid solution,and eventually devour other oriented grain becomes the stable texture of the solid solution state,The evolution of texture in secondary cold rolling is {113}<121> by {012}<100>→{011}<100>→{011}<211>;shear area will make {112}<111> and {123}<523> turn to {011}<100> and {123}<634>,and flow into{011}<211> finally.