锆合金中氢化物的结构和弹性性能: 结合第一性原理计算和实验

Structures and Elastic Properties of Hydrides in Zirconium Alloys: First-Principle Calculations and Experiments

摘要:

采用第一性原理计算和实验方法研究了α-Zr及其氢化物的结构和弹性性能。考虑到所有可能的H-原子构型，构建了不同相的氢化物模型。结果表明，γ、δ和ε氢化物的稳定结构分别为P4₂/mmc、P4₂/nnm和I4/mmm。计算结果表明，ε氢化物的生成焓最低，并提出了γ→δ→ε的相变顺序。与α-Zr相比，氢化物的c轴晶格常数变小，γ、δ和ε单位胞的膨胀体积分别为12.1%、14.8%和17.9%。3种氢化物的计算弹性模量（E）均低于α-Zr，但弹性各向异性均高于α-Zr。通过纳米压痕实验分析了α-Zr基体和δ氢化物的弹性性能，结果表明，α-Zr基体和δ氢化物的E分别为116.88和111.01 GPa。因此，在氢化物/基体界面的氢化物侧容易发生应力集中，氢化物容易成为裂纹源，导致锆合金发生脆性断裂。

Abstract:

The structure and elastic properties of α-Zr and its hydrides were investigated by first-principle calculations and experimental methods. Considering all possible H-atom configurations, different phase models of hydrides were constructed. Results show that the stable structures of γ, δ and ε hydrides are P4₂/mmc, P4₂/nnm and I4/mmm, respectively. Calculation results suggest that ε hydride has the lowest formation enthalpy, and the phase transition sequence of γ → δ → ε is proposed. Compared with those of α-Zr, the c-axis lattice constants of hydrides become smaller, and the expansion volumes of γ, δ and ε unit cell are 12.1%, 14.8% and 17.9%, respectively. The calculated elastic modulus (E) of the three hydrides are lower than that of α-Zr, but their elastic anisotropy is higher than that of α-Zr. The elastic properties of α-Zr matrix and δ hydride were analyzed by nanoindentation experiment and the results show that E of the α-Zr matrix and δ hydride is 116.88 and 111.01 GPa, respectively. Therefore, the stress concentration is easy to occur on the hydride sides near the hydrides/matrix interface, so the hydrides are more likely to be the sources of crack and cause brittle fracture of zirconium alloys.