Study On The Deformation Mechanism Of Dual-phase Magnesium Alloy Based On Interface Defects

Magnesium(Mg)alloy has many excellent properties,such as low density,high specific strength and favorable recyclability.It is mainly used in electronic products,automobile and aerospace fields.However,the poor plastic deformability of Mg alloys at room temperature seriously hinders the large-scale application of Mg alloys in industry,which mainly stems from the fact that the number of independent slip-system for the Mg alloys is insufficient at room temperature.Nanoscale amorphous alloys exhibit a remarkable plasticity.Previous study reported that the introduction of nanoscale amorphous into Mg alloys can effectively improve the strength and plasticity of Mg alloys simultaneously,which is mainly ascribed to the synergistic mechanism of the crystalline phase and amorphous phase of the dual-phase Mg alloys during deformation.In addition,during the plastic deformation of Mg alloys,apart from the well-established conventional dislocation glide and deformation twining mechanisms,the new grain(i.e.crystalline reorientation)is also the common mode of its plastic deformation whose interface is composed of basal/prismatic interface and(10(?)2)twin boundary.However,the effect of basal/prismatic interface and(10(?)2)twin boundary on the deformation mechanism of the dual-phase Mg alloys is still unclear,and the solution of these problems will be of great significance to the design of highperformance dual-phase Mg alloys.In this work,the molecular dynamics simulation is employed to explore the effect of basal/prismatic interface and(10(?)2)twin boundary on the deformation mechanism and mechanical properties of the dual-phase Mg alloys under uniaxial tensile loading.The main contents and conclusions are as follows:(1)The effect of basal/prismatic interface on the deformation mechanism of the dual-phase Mg alloys here is investigated.The results indicate that the crystalline/amorphous interface(CAI)have a significant Peach-Koehler(attractive or repulsive)force to govern the activation of interfacial dislocations on basal/prismatic interface.When the spacing between CAI and BPI(SAB)is less than 12.0 nm,it is found that the attractive force exerted by CAI has an effect on the activation of interfacial dislocations.On the contrary,the repulsive force controls interfacial dislocation activation when SAB is greater than 12 nm.The results also show that the strain corresponding to the maximum peak stress increases almost linearly with increasing SAB,which is mainly attributed to the increase of strain contributed by basal/prismatic interface migration.(2)The effect of(10(?)2)twin boundary on the deformation mechanism of dualphase Mg alloys here is also explored.The results show that the twin boundary can induce the activation of dislocation slip and HCP→FCC phase transformation,which can effectively facilitate the synergy interaction between the crystalline phase and amorphous phase and enhance the plastic deformability of the dual-phase Mg alloys.However,the twin boundary increases the plasticity of dual-phase Mg alloys at the expense of strength.To design high performance dual-phase Mg alloys,the effect of the spacing between the twin boundary and CAI(STC)on the mechanical properties of the dual-phase Mg alloys is also studied.It is worth highlighting that the yield strength of the dual-phase Mg alloys increases with the increase of STC.The simulations indicate that the high-strength and high-plasticity dual-phase Mg alloys can be obtained by introducing twin boundary and optimizing STCs.