Study Of Anisotropic Behavior In Dual-Phase Brass By Neutron Diffraction

From the mechanical points of view,materials represent some anisotropic behaviors when the plastic deformation occurs or if the material is textured.These anisotropies of polycrystalline materials are a result of the typeⅡstress,which affects the lattice distortion,rotation and yield of the crystal grains.Understanding the typeⅡstress of materials can provide better guidance for basic research and engineering applications.Diffraction methods are excellent non-destructive stress detection techniques.Compared with X-ray diffraction,neutrons have stronger penetrating ability due to their electrical neutrality.They can measure larger-volume samples and obtain typeⅡand typeⅢstress information inside the sample.At present,sin2ψmethod and d₀ method are common diffraction methods to measure internal stress of materials.However,these methods cannot reflect the stress distribution of materials accurately as they do not measure anisotropic behavior.The texture-components-dependent method can track the three-dimensional stress tensor information of different grain components,which can more accurately reflect the anisotropy of the material.In this paper,the two-phase polycrystalline material brass with a relatively simple structure is selected as the research object,neutron diffraction technology and texture-components-dependent method are applied to study the anisotropic behavior of the grains in two phases with different components during uniaxial stretching,and the mechanism of their anisotropy are discussed.In the process of research,neutron diffraction is used to track the texture evolution and stress information of the sample under load.Afterwards,the diffraction analysis is carried out to determine the texture of the brass sample before and after deformation.The stress tensor of each component in two phases is calculated by texture-components-dependent method.Finally,combined with the constitutive relationship of anisotropic materials,the mechanism of anisotropic behavior of dual-phase brass is studied.The measurement and calculation results of neutron diffraction shows that grains of each component are mainly subjected to normal stress σ₁₁,σ₂₂ and σ₃₃,and the stress tensors vary in different components under the same macroscopic stress.Combining the single crystal elastic constants,diffraction elastic constants,texture evolution,and Schmid factor calculated from the anisotropic polycrystalline mechanics analysis and the experimental results,it can be concluded that（111）crystal plane has the greatest hardness,and crystal grains will have the greatest tensile strength when their（111）plane is perpendicular to the tensile direction.Understanding the distribution difference of stresses between different components is of great significance for studying the anisotropic properties of materials,and has important reference value for solving the design and processing problems of materials.