Research On Micro-mechanism Of Twinning And Related Plastic Deformation Behavior For Magnesium

Mg alloys are attracting much attention as popular light materials.However,Mg and its alloys belong to the HCP structure which have limited number of slip systems available for dislocation glide;so it exhibits low ductility and low plastic formability.Thus,twinning deformation is one of the important deformation modes for plastic deformation in hexagonal close-packed(hcp)metals such as Mg,and it strongly affects the mechanical properties.Therefore,deformation twins and other related issues of HCP structure metals have attracted the attention of many scholars.In order to more thoroughly study the common twinning deformation behavior and related plastic deformation mechanism of mg,the method of molecular dynamic simulation is used from the aspect of microscopic atomic movement and dislocation slip;so the analysis of the nucleation and growth of twins is more comprehensive and thorough.It provides a theoretical support for the processing and forming of magnesium and its alloys,and guides the actual production process.In this paper,the anisotropy of mg was studied firstly.The LAMMPS software was used to simulate the process of compressing single crystal magnesium along different orientations and the plastic deformation modes of single crystal magnesium during the compression process were analyzed to understand the cause of the anisotropy of metal magnesium.Moreover,compression deformation along the c-axis direction are mainly slip and {10(?) 1} twinning deformation,while compression deformation along the direction of vertical c-axis are mainly {10(?) 2} twinning deformation and {10(?) 1} secondary twinning deformation.Secondly for the common plastic deformation mode of magnesium--twining deformation,the twin atomic motion and the dislocation slip mechanism for {10(?)2} and {10(?)1} twinning of magnesium were studied in this paper.The result shows that the {10(?)2} twin atoms mainly have mutual conversion between the {0002} basal plane and the {10(?)0} cylinder plane.It is also found that the {10(?)2} twin is the result of two kinds of imperfect dislocation slipping together.The Burgers Vector is b=1/3<10(?)0>.The dislocation slipping mechanism has also been verified by transmission electron microscopy(TEM)experiment.The {10(?)1} twin atoms mainly have mutual conversion between the {0002} basal plane and the {10(?)1} pyramidal plane.It is also found that the {10(?)1} twin is the result of imperfect dislocation slipping at interval of two atomic layers.The Burgers Vector is also b=1/3<10(?)0>.At last,the mobility of twin boundary for {10(?)2} twin and {10(?)1} twin were simulated.The result shows that the {10(?)2} twin boundaries are easier to move and the migration of {10(?)2} twin boundaries presents ?bow? shape mode;while the {10(?)1} twin boundaries migrate with ?step? mode.It is also found that there are a large number of periodic interfacial dislocations on the {10(?)1} twin interface and the interfacial dislocations will hinder the movement of twin interface.This phenomenon has been also further verified by transmission electron microscopy(TEM)experiment.