Department of Physics, National University of Singapore, Singapore, 117551, Singapore.
Centre for BioImaging Sciences, Department of Biological Sciences, National University of Singapore, Singapore, 117557, Singapore.
Nat Commun. 2023 Jan 6;14(1):104. doi: 10.1038/s41467-022-35325-y.
Two most common crystal structures in metals and metal alloys are body-centered cubic (bcc) and face-centered cubic (fcc) structures. The phase transitions between these structures play an important role in the production of durable and functional metal alloys. Despite their technological significance, the details of such phase transitions are largely unknown because of the challenges associated with probing these processes. Here, we describe the nanoscopic details of an fcc-to-bcc phase transition in PdCu alloy nanoparticles (NPs) using in situ heating transmission electron microscopy. Our observations reveal that the bcc phase always nucleates from the edge of the fcc NP, and then propagates across the NP by forming a distinct few-atoms-wide coherent bcc-fcc interface. Notably, this interface acts as an intermediate precursor phase for the nucleation of a bcc phase. These insights into the fcc-to-bcc phase transition are important for understanding solid - solid phase transitions in general and can help to tailor the functional properties of metals and their alloys.
在金属和金属合金中，最常见的两种晶体结构是体心立方（bcc）和面心立方（fcc）结构。这些结构之间的相变在生产耐用和功能性金属合金方面起着重要作用。尽管它们具有重要的技术意义，但由于探测这些过程所带来的挑战，这些相变的细节在很大程度上仍不为人知。在这里，我们使用原位加热透射电子显微镜描述了 PdCu 合金纳米粒子（NPs）中 fcc 到 bcc 相变的纳米细节。我们的观察结果表明，bcc 相总是从 fcc NP 的边缘开始形核，然后通过形成一个独特的几原子宽的相干 bcc-fcc 界面在 NP 中传播。值得注意的是，这个界面充当了 bcc 相形核的中间前体相。这些对 fcc 到 bcc 相变的深入了解对于理解一般的固-固相变很重要，并有助于调整金属及其合金的功能特性。
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