Phase field study of the grain size and temperature dependent mechanical responses of tetragonal zirconia polycrystals: A discussion of tensioncompression asymmetry
Phase field study of the grain size and temperature dependent mechanical responses of tetragonal zirconia polycrystals: A discussion of tensioncompression asymmetry
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四方氧化锆多晶的晶粒尺寸和温度依赖性机械响应的相场研究：拉伸压缩不对称性的讨论
DOI：
10.1016/j.commatsci.2019.109326
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发表时间：
2020
影响因子：
3.3
通讯作者：
Sun Yuanzun
中科院分区：
文献类型：
--
作者：
Zhu Jingming;Luo Jun;Sun Yuanzun
在本文中，通过相场（PF）建模研究了四方氧化锆多晶（TZP）在单轴拉伸和压缩下的不对称机械响应。之前的四方到单斜 (t-m) 相变 PF 模型（Mamivand 等人，2013）经过修改，可以表征晶粒尺寸效应和环境温度的影响。提出了一种基于四阶朗道多项式的修正化学自由能泛函，以正确描述不同环境温度下t-m相变的能垒。此外，还提出了热力学方法来描述晶界对 t-m 转变的抑制作用。马氏体孪晶之间的界面能也不同于奥氏体-马氏体界面处的界面能。然后进行 PF 模拟，将 TZP 的微观结构演变与加载周期期间的机械响应联系起来。特别是，比较和讨论了 TZP 在拉伸和压缩加载循环下的不对称机械响应。结果表明，改进的 PF 模型可以很好地表征 TZP 的微观结构演化过程以及晶粒尺寸和温度依赖性应力应变响应。对于两种类型的载荷，TZP 在低于平衡温度时表现出形状记忆效应 (SME)，在高于奥氏体转变温度时表现出伪弹性。系统地讨论了晶粒尺寸效应和环境温度对TZPs微观结构演化过程的影响以及单轴拉压下TZPs的应力应变响应特征。结果表明，TZPs 的拉压不对称性主要归因于伴随 t-m 相变的膨胀转变应变。
In this paper, the asymmetric mechanical responses of tetragonal zirconia polycrystals (TZPs) under uniaxial tension and compression are investigated by phase field (PF) modelling. The previous PF model for the tetragonal to monoclinic (t-m) phase transformation (Mamivand et al., 2013) is modified to characterize the grain size effect and the influences of ambient temperature. A modified chemical free energy functional based on the fourth-order Landau polynomial is proposed to properly describe the energy barrier of the t-m phase transformation at different ambient temperatures. In addition, a thermodynamic approach is proposed to describe the suppression effect of the grain boundaries on the t-m transformation. The interfacial energy between the martensitic twins is also differentiated from that at the austenite-martensite interface. PF simulations are then carried out to relate the microstructure evolution of TZPs with the mechanical responses during a loading cycle. In particular, the asymmetric mechanical responses of TZPs under tensile and compressive loading cycles are compared and discussed. It is demonstrated that the modified PF model can well characterize the microstructural evolution process as well as the grain size and temperature dependent stress-strain responses of TZPs. For both types of loadings, TZPs exhibit shape memory effect (SME) below the equilibrium temperature and pseudoelasticity above the austenite transition temperature. The grain size effect and the influences of ambient temperature on the microstructural evolution process and the characteristics of the stress-strain responses of TZPs under uniaxial tension and compression are systematically discussed. It is revealed that the tension-compression asymmetry of TZPs is mainly attributed to the dilatational transformation strain accompanying the t-m phase transformation.