Ferroelastic toughening of single crystalline yttria-stabilized t ' zirconia: A phase field study
Ferroelastic toughening of single crystalline yttria-stabilized t ' zirconia: A phase field study
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单晶氧化钇稳定氧化锆的铁弹性增韧：相场研究
DOI：
10.1016/j.engfracmech.2020.107077
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发表时间：
2020
影响因子：
5.4
通讯作者：
Zhu Jingming
中科院分区：
文献类型：
--
作者：
Sun Yuanzun;Luo Jun;Zhu Jingming
具有四元相（t '-YSZ）的氧化钇稳定的氧化锆最广泛地用于热障涂层。本文提出了一个简明的二维相场模型来模拟单晶t '-YSZ中的畴变，其中明确地考虑了畴变的能垒。畴变的矫顽应力可以很容易地通过调节畴变的能垒来调节。在此基础上，将新的畴变PF模型与已有的断裂PF模型相结合，建立了耦合PF模型。耦合PF模型可以同时模拟畴变和裂纹扩展，而无需任何自组织准则。然后用PF模拟研究了在不同类型的载荷下单晶t '-YSZ中边缘裂纹的扩展。系统地讨论了晶体取向和加载方式对裂纹扩展和畴变的影响。通过对裂纹尖端应力场的分析，验证了畴变区的分布。当初始t'相的轴与裂纹面平行或垂直时，由于模型的对称性，裂纹以I型扩展。为了定量评估铁弹增韧，计算了能量释放率（ERR）沿着裂纹扩展，其中逐步位移载荷施加到数值模型。在每一个加载步骤，裂纹可以达到平衡状态，其中的能量释放率等于裂纹扩展阻力。通过计算每个加载步骤的能量释放率，揭示了畴变的铁弹增韧效应，并定量表征了其特征。结果表明，t'相的畴变对裂纹扩展有明显的增韧作用。除了晶体取向外，加载方式也会对畴变和增韧效果产生明显影响。对于与裂纹表面不对称的晶体取向，由于畴变区的不对称分布，裂纹可能会偏转。本文建立的耦合PF模型可以作为表征单晶t'氧化锆断裂行为和铁弹增韧效应的有效数值工具。
Yttria stabilized zirconia with the tetragonal prime phase (t'-YSZ) is most widely used in thermal barrier coatings. In this paper, a concise 2D phase field (PF) model is proposed to simulate domain switching in single crystalline t'-YSZ, where the energy barrier for domain switching is explicitly considered. The coercive stress for domain switching can be easily tuned by adjusting the energy barrier for domain switching. After that, a coupled PF model is developed by combing the new PF model for domain switching and the existing PF model for fracture. The coupled PF model can simulate the domain switching and crack propagation simultaneously without any ad-hoc criteria. The propagation of an edge crack in single crystalline t'-YSZ under different types of loadings are then studied with PF simulations. The influences of crystalline orientation and loading types on crack propagation and domain switching are systematically discussed. The distribution of the domain switching zone is validated by analyzing the stress field around the crack tip. When thec-axis of the initial t' phase is in parallel with or perpendicular to the crack surface, the crack propagates in mode I due to the symmetry of the model. In order to assess the ferroelastic toughening quantitatively, the energy release rate (ERR) along with the crack growth is calculated, where a stepwise displacement load is applied to the numerical model. At each load step, the crack can reach the equilibrium state, where the energy release rate equals the crack growth resistance. By computing the energy release rate at each load step, the ferroelastic toughening effect of domain switching is revealed and quantitatively characterized. It is shown that the domain switching of the t' phase can produce obvious toughening effect on crack propagation. Besides crystal orientation, loading types can also have distinct influences on domain switching and the toughening effect. For crystal orientations asymmetric to the crack surface, the crack may deflect due to the asymmetric distribution of the domain switching zone. The coupled PF model developed in this paper can act as an effective numerical tool to characterize the fracture behavior and ferroelastic toughening effect of single crystalline t' zirconia.