In-Situ Study On Plastic Deformation Mechanism Of Bicrystalline Copper Under Uniaxial Tensile

Copper and its alloys are widely used as metal structural materials in the industrial field,and the stress conditions are complex under the dynamic and static loads during service.The deformation behavior of bicrystal is the basis for understanding mechanical behavior of polycrystalline materials and it can provide experimental as well as theoretical basis for studying the plastic deformation of polycrystalline copper.The evolutionary behavior of slip bands was studied by in-situ scanning electron microscopy?In-situ SEM?combined with digital image correlation?DIC?during plastic deformation.The results show that grain boundary and grain orientation make great influence on the generation and evolution of slip bands.The normal strain field E_xxx reveals that the single and double slip systems are activated at two grain interiors and grain boundary?GB?vicinity,respectively.The slip bands lead to unhomogeneity of local strain,and increase in numbers and decrease in intensity with increasing tensile strain,therefore the deformation gets more and more homogenous.The single slip system tends to be activated in softer grain[50-1],so the slip bands are much more in number and distribute homogenously.While harder grain[1-53]tends to active double slip systems and the slip bands are less in number but larger in intensity?strain?.Softer grain has larger normal strain E_xxx than harder grain,and their difference are amplified after 8%tensile strain,resulting the higher mediated stress caused by GB and sharp increase of shear strain E_xyy at GB vicinity.The amplitude of shear strain field E_xyy is much smaller than that of normal strain field E_xx,and the value of shear strain at GB vicinity is higher than it within grain interiors.The in-situ electron backscattered diffraction?In-situ EBSD?was used to study the lattice rotation behavior of bicrystal copper during plastic deformation.The results show that grain boundary and grain orientation play important roles in rotation behavior of grains.Significant rotation occurs in different areas before 25%tensile strain.After 25%tensile strain,the lattice rotation mainly occurs at GB vicinity.Orientation within softer grain vicinity changed from[112]towards the line of[001]-[111],which satisfying the Sachs model.While the lattice rotation behavior near GB do not match either Sachs model or Taylor model.The orientations of harder grain vicinity are always distributed around[001],which satisfying Taylor model.The distribution of shear strain near GB affects the rotation behavior of local lattice,and lattice rotation can change Schmid factor distribution.Geometrically necessary dislocations maps as well as image quality maps indicate that the most uneven deformation occurs at grain boundary during deformation.