Simulation Study On Interaction Mechanism Between Dislocation And Amorphous Phase In Dual-Phase Alloys

Amorphous/crystalline nano-dual-phase structure provides a new approach for the development of ultra-high-strength and high-toughness advanced magnesium(Mg)alloys and high-entropy alloys(HEAs).Recently,scholars at home and abroad have successively prepared high-performance dual-phase Mg alloys and dual-phase HEAs experimentally,but the basic strengthening mechanism and deformation mechanism of the dual-phase Mg alloys and HEAs require additional research to be further revealed.In particular,the mechanism of interaction between dislocation and amorphous phase and its influence on the mechanical properties of alloy materials are still unclear.Therefore,it is of great significance to understand the strengthening and toughening mechanism of amorphous/crystalline dual-phase Mg alloys and HEAs from the atomic scale,to reveal the interaction mechanism between dislocation and amorphous phase,and to provide relevant theoretical guidance for the design and preparation of dual-phase alloy materials with excellent properties.In this paper,taking Mg alloys and HEAs as the research objects,the molecular dynamics simulation method is used to study the interaction behavior of dislocation and amorphous phase under shear loading,clarifying the size and spacing of amorphous phase,the composition of crystal phase,and the effect of temperature on mechanical behavior and deformation mechanism of dual-phase alloys.The main research contents and conclusions are as follows:(1)The effect of the size of amorphous nanopillar on the mechanical properties and deformation behavior of Mg alloys is investigated.The results show that the strengthening effect of amorphous nanopillar on the Mg alloys is dependent on the size of the amorphous nanopillar.The small-size amorphous nanopillar as an obstacle has a weak blocking effect on dislocation slip,so the dislocation easily detaches from the amorphous nanopillar and recover to a perfect full dislocation.The resistance of amorphous nanopillar to dislocation slip is mainly due to the attraction between the dislocations and amorphous/crystalline interface.The study found that an unconventional mechanism caused by extended dislocations appears when dislocation interacts with amorphous nanopillar,which is different from the traditional shear mechanism and Orowan mechanism of the interaction between dislocation and crystalline precipitates.(2)The effect of the rare earth element Y content in the Mg alloys on the interaction mechanism of dislocation and amorphous nanopillar is investigated.The results show that Y content has a significant effect on the interaction mechanism between prismatic<a>dislocation and amorphous nanopillar.When Y content is less than 2%,the solid solution strengthening caused by Y is less than the dislocation strengthening caused by the extended dislocations in pure Mg,so the depinning stress of pure Mg is greater than the Mg-Y1% and Mg-Y2% models.However,when Y content is greater than 2%,the high concentration of Y increases the difficulty of basal plane <a> slip,preventing the perfect prismatic dislocation from decomposing into the extended dislocation on the basal plane.The results show that the extended dislocation strengthening has little effect on the increase of depinning stress,but the solid solution strengthening effect is significantly enhanced,so the depinning stress of pure Mg is less than the Mg-Y3% and Mg-Y4% models.(3)The effects of amorphous nanopillar size,amorphous nanopillar spacing and temperature on the behavior of expanded dislocation overcoming amorphous obstacle in HEAs are investigated.The results indicate that different from traditional pure metals,the width of the extended dislocation of the HEA fluctuates violently during the shear deformation,and the partial dislocation lines are wavy lines rather than straight lines.The curved dislocation line can interact with more solute atoms,so as to further increase the resistance of dislocation movement,which contributes to the strain strengthening of the HEA.The results of the study point out that the introduction of amorphous nanopillar can significantly improve the strength of the HEA.The larger the amorphous nanopillar size(or the smaller the amorphous nanopillar spacing),the longer the pinning time of dislocation,the higher the depinning stress of dislocation,that is,the more obvious the strengthening effect.The results also indicate that with the increase of temperature,the critical shear stress of dislocation slip and the blocking effect of amorphous nanopillar on dislocation is decrease significantly,which is due to the decrease of the strength of the crystalline and amorphous phases at higher temperature.