Effect Of Texture On Properties And Residual Stress In Cu-Ni-Si Alloys And Its Mechanism

Cu-Ni-Si alloys are widely used in the manufacture of lead frames and packaging materials for integrated circuits because of their high strength,high elasticity,and excellent electrical conductivity.With the continuous development of electronic information products to small,thin,lightweight,multifunctional and intelligent,integrated circuits are developing in the direction of large-scale and ultra-large-scale,which prompts the lead frame to have high strength,high elasticity,and high conductivity.It also needs to have good plasticity and forming properties,that is,good flatness and low residual stress.The mechanical properties,electrical conductivity and internal residual stress distribution of the plate and strip are closely related to the texture.This paper systematically studied the evolution of the microstructure and texture of Cu-Ni-Si alloys under different heat treatment processes,as well as the effect of texture on properties and residual stress.And established a comprehensive evaluation system for texture,mechanical and electrical properties,and macroscopic and microscopic residual stress.The effects of hot rolling,solid solution,cold rolling and aging processes on the texture evolution of Cu-Ni-Si-Co alloys are studied in detail,and the texture strengthening mechanism and conductive mechanism are analyzed from the mechanism.The preferred orientation of the grains in the hot-rolled sheet is not obvious.The large-deformation cold-rolled sheet mainly contains copper texture and R-shaped texture.The solution treatment makes the preferred orientation of the crystal grains disappear,and the effect on the Copper texture is more obvious.The aging board mainly contains R-type texture,and the content exceeds 40%.When the grain orientation is close to the[111]crystal plane,it is located in the hard orientation zone,the Schmid value is smaller,and the strength of the material is larger.At the same time,the[111]crystal plane is a densely packed plane,and the conductivity is also better.The texture close to the[100]crystal plane is located in the soft orientation zone,and its mechanical and electrical properties are opposite.The effects of multiple deep cold rolling and low temperature aging processes on the properties and texture evolution of the deformed Cu-Ni-Si-Co alloy are discussed.The structure characteristics and strengthening mechanism of dislocations,precipitates and twins in the alloy are also described.The tensile strength and electrical conductivity of the alloy reached 937.27 MPa and 45.57%IACS,respectively,and it has good stress relaxation resistance.The metamorphic alloys mainly contain Brass,R-type and Copper textures,and their volume contents are 30.2%,29.2%and 20.3%,respectively.There are a large number of dislocation entanglements,dislocation lines,dislocation cells and deformed twins in the alloy.The alloy contains both 300-600 nm coarse particle precipitates and 5-10 nm rod-like nano precipitated phases,the composition of which is(Ni,Co)2Si.The average dislocation density in the morphological samples at 350?/2 h is about(35.967±1.513)× 1014 m-2,and the probability of stacking fault or twinning is about(14.414±0.333)×10-3.Based on the diffraction results of XRD and HEXRD(high energy synchrotron radiation),the interaction stress model between Voigt and Reuss grains has been revised,so that it can more accurately characterize the residual stress in the texture sample.For Cu-Ni-Si-Co alloy,the residual stress is positively correlated with Young's modulus,so the residual stress measured by the(111)diffraction crystal plane is larger.It shows that the residual compressive stress has the largest distribution on the face-centered cubic close-packed surface.Based on the classic X-ray diffraction sin2? method for measuring residual stress,a method for calculating residual stress with weighted average significance is proposed for textured materials,which provides a new idea and new method for measuring the residual stress of textured materials by X-ray.Based on the nanoindentation method and the FIB-DIC ring core method,the relationship between the micro-texture and micro-residual stress of Cu-Ni-Si-Co alloy was studied.The Young's modulus and residual stress on the orientation close to the[111]crystal plane is larger,that is,the densely packed(111)crystal plane has the effect of concentrating the stress.The Young's modulus and residual stress near the[100]crystal plane is relatively small,indicating that the[100]grain orientation has the effect of buffering the residual stress.In addition,the influence of large deformation and broken sub-grain on the residual stress distribution is higher than the influence of crystal orientation.This paper uses texture as a bridge to define a weighted correlation model between macroscopic stress and microscopic stress,and expands the basic theory of texture's influence on residual stress.