Molecular Dynamics Simulation Of Twin Deformation In TWIP Steel

With the development of energy and environmental demand for high-strength steel in the automotive field,twin-induced plastic steel has broad application due to its excellent mechanical properties.Twins-induced plastic steel's excellent comprehensive mechanical properties are derived from the role played by twins during deformation.Due to the limitations of conditions,it is difficult to study the physical experiments of twins at the atomic or molecular scale.Based on the potential function of the TWIP steel proposed by the scientific method,the effects of deformation conditions such as deformation temperature,tensile rate,and cracks on the tensile deformation of the twins in the TWIP steel were simulated in this paper.The effects of different deformation temperatures of 200 K,300K,400 K,500K and600 K on twin tensile deformation in TWIP Steel were studied.The results show that the young's modulus decreases linearly with the increase of deformation temperature,and the yield strength decreases gradually.Compared with the yield strength at 200 K,the yield strength at 300 K and 400 k decreases by 1.8% and 2.8% respectively,while the yield strength at 500 K and 600 k decreases 13% and 18.4% respectively.When the temperature is 300?400K,the deformation mode is mainly twinning,and when the temperature is500?600K,the deformation mode is mainly dislocation slip.The effects of different tensile rates of 0.03(?)/ps,0.3(?)/ps,1(?)/ps and 3(?)/ps on twin tensile deformation in TWIP steel were studied.The results show that with the increase of tensile rate,the yield strength of the specimens increases,while the young's modulus is unchanged.The influence of crack on twin tensile deformation in TWIP Steel was studied from crack positions: transverse crack,longitudinal crack and internal crack,from deformation temperature of 200 K,300K,400 k,500K and 600 K,from tensile rate 0.3(?)/ps,0.5(?)/ps,0.7(?)/ps and 1(?)/ps.The results show that the crack perpendicular to the tensile direction has a great influence on the deformation process.Temperature has an effect on the shape of deformation twins at the crack tip.At low temperature,the volume of deformation twins formed at the crack tip is large and the number of deformation twins is single.With the increase of temperature,the volume of deformation twins at the crack tip decreases,the number of twin boundaries increases and the spacing decreases.Under different tensile rates,the mode of crack growth is dislocation slip and twinning.A mechanism for conducting dislocation orientation transition by stair-rod dislocation is observed.When the direction of any partial dislocation connected with the stair-rod dislocation changes to the opposite direction,this change of direction can be transmitted through the constant stair-rod dislocation.From the perspective of stacking fault,the stacking faults of different orientations connected with each other gradually disappear in order.The mechanism of deformation twin nucleation and growth is the slip of Shockley incomplete dislocation.The strengthening mechanism of TWIP Steel during deformation includes the interaction of twin and twin,the interaction of twin and dislocation and the interaction of stacking fault and dislocation.