单轴拉伸下氧化锆纳米柱相变机理的分子动力学研究

Molecular dynamics study on phase transition mechanism oftetragonal zirconia nanorods under uniaxial tension

通过分子动力学模拟,观察到[001]取向的四方氧化锆纳米柱在拉伸载荷下具有两个线弹性变形的应力-应变关系.这一现象是四方结构向单斜结构相变的结果 .为了进一步阐明应力-应变曲线,进行了包括晶体结构分析和原子应变计算在内的详细研究.晶格取向强烈影响塑性变形机制,即[001]和[111]取向的纳米柱在拉伸载荷下经历相变,而沿[110]取向的纳米柱导致脆性断裂.观察到显著的温度效应,随着温度从300K升高到1500K,弹性模量从573.45GPa线性降低到482.65GPa.此外,还用轻推弹性带(NEB)理论估算了相变能垒,观察到相变能垒随温度的升高而降低.这一工作将有助于加深对氧化锆的四方相到单斜相转变和纳米尺度力学行为的理解.

Through molecular dynamics simulation, it is observed that the [001] oriented tetragonal zirconia nanopillars have two linear elastic deformation stress-strain relationships under tensile load. This phenomenon is the result of the phase transition from tetragonal structure to monoclinic structure. In order to further clarify the stress-strain curve, detailed studies including crystal structure analysis and atomic strain calculation were performed. The lattice orientation strongly affects the plastic deformation mechanism, that is, the [001] and [111] oriented nanopillars undergo phase transition under tensile load, while the [110] oriented nanopillars lead to brittle fracture. A significant temperature effect was observed. As the temperature increases from^(3)00K to 1500K, the elastic modulus decreased linearly from 573.45GPa to 482.65GPa. In addition, the phase transition energy barrier is estimated by the light elastic band (NEB ) theory, and it is observed that the phase transition energy barrier decreases with increasing temperature. This work will help to deepen the understanding of tetragonal to monoclinic phase transition and nano-scale mechanical behavior of zirconia.