Atomic-resolution observation of crystal growth in metallic glass nanorods
Crystallization induced microstructure plays a central role in tailoring materials properties, yet our understanding of its formation process is limited due to its complexity. Classical crystallization theories assume that nucleation and growth are separate processes in which thermodynamically unstable clusters fluctuate in the nucleation stage, but do not participate in the later growth. Here, we apply in situ aberration-corrected transmission electron microscopy (TEM) technique to directly observe the crystal growth of metallic glass nanorods at the atomic resolution and test the classical theories. Surprisingly, we show that, at the atomic scale, the isothermal growth rate for a single crystalline phase is asymmetric upon thermal history. This observation is in direct contrast to what would be expected based on classical theories. We further observe that the asymmetric growth rate depends on the diameter of the nanorod. Thus, our in situ TEM observations mark departure from classical theories.
Yujun Xie is currently a 4th year PhD student in Mechanical Engineering and Materials Science at Yale University. He received his B.S. in Materials Science and Engineering from Drexel University in 2014. His research interests focus on using in situ transmission electron microscopy to investigate the underneath crystallization mechanism in metallic glass and phase change materials and provide insight on relevant engineering problems.