堆垛层错和温度对纳米多晶镁变形机理的影响

The effects of stacking fault and temperature on deformation mechanism of nanocrystalline Mg

本文采用分子动力学模拟方法研究了在拉伸载荷下,堆垛层错和温度对纳米多晶镁力学性能的影响.在模拟中,采用嵌入原子势描述镁原子之间的相互作用.计算结果表明:在纳米晶粒中引入堆垛层错能明显增强纳米多晶镁的屈服应力,但堆垛层错对纳米多晶镁杨氏模量的影响很小;温度为300.0K时,孪晶在晶粒交界附近形成,孪晶随着拉伸应变的增加而逐渐生长.当拉伸应变达到0.087时,一种基面与X-Y面成大约35°角且内部包含堆垛层错的新晶粒成核并快速增长.也就是说,孪晶和新晶粒的形成和繁殖是含堆垛层错的纳米多晶镁在300.0K温度下的主要变形机理.模拟结果也显示,当温度为10.0K时,位错的成核和滑移是含堆垛层错的纳米多晶镁拉伸变形的主要形式.

The effects of stacking fault （SF） and temperature on the mechanical properties of nano-polycrystal Mg under tension loading are investigated by molecular dynamics simulations. The interatomic potential of embedded atom method （EAM） is used as the Mg-Mg interaction. The computational results show that the yield strength of nano-polycrystal Mg can be obviously enhanced when stacking fault is introduced into grains, and the effect of SF on the Young＇s modulus of nano-polycrystal Mg is very small. The results also show that tensile twins and neff grain at 300.0 K are nucleated and initiated at grain boundaries, growing continuously with the increase of strain. The dihedral angel between the （1000） plane of new grain and the x-Y plane is about 35~. In other words, the nucleation and the growth of twins and new grains are the predominant deformation mechanism for nano-polycrystal Mg at 300.0K. We also find that at 10.0K the dislocation nucleation and slip are the predominant modes of the plastic deformation for nano-polycrystal Mg.