As theoretically hypothesized for several decades in group IV transition metals, we have discovered a dynamically stabilized body-centered cubic (bcc) intermediate state in Zr under uniaxial loading at sub-nanosecond timescales. Under ultrafast shock wave compression, rather than the transformation from α-Zr to the more disordered hex-3 equilibrium ω-Zr phase, in its place we find the formation of a previously unobserved nonequilibrium bcc metastable intermediate. We probe the compression-induced phase transition pathway in zirconium using time-resolved sub-picosecond x-ray diffraction analysis at the Linac Coherent Light Source. We also present molecular dynamics simulations using a potential derived from first-principles methods which independently predict this intermediate phase under ultrafast shock conditions. In contrast with experiments on longer timescale (> 10 ns) where the phase diagram alone is an adequate predictor of the crystalline structure of a material, our recent study highlights the importance of metastability and time dependence in the kinetics of phase transformations.

正如在IV组过渡金属中数十年的理论假设一样，我们发现了在亚纳秒级的单轴载荷下Zr中动态稳定的体心立方（bcc）中间态。在超快冲击波压缩下，我们发现形成了以前未观察到的非平衡bcc亚稳态中间体，而不是从α-Zr转变为更无序的hex-3平衡ω-Zr相。我们在线性加速器相干光源处使用时间分辨的亚皮秒X射线衍射分析来探测锆中的压缩诱导的相变途径。我们还介绍了分子动力学模拟，它使用了从第一性原理方法获得的电势，该方法可独立预测超快冲击条件下的中间相。