Nakayama Koji S, Nishijima Masahiko, Zhang Yicheng, Chen Chuantong, Ueshima Minoru, Suganuma Katsuaki
F3D, The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka, 567-0047, Japan.
Daicel Corporation, 2-18-1, Konan, Minato-ku, Tokyo, 108-8230, Japan.
Sci Rep. 2024 Sep 3;14(1):19618. doi: 10.1038/s41598-024-70298-6.
Metastable phases such as supersaturated solid solutions, supercooling, and amorphous phases are well-known in metallurgy. They are often composed in non-equilibrium states and can be transformed into a stable phase by overcoming an energy barrier with driving forces. Particularly, it has been widely used for material strengthening and heterogeneous nucleation of precipitates in solids is mainly induced by heat treatments for supersaturated solid solutions. However, little is known about the metastable phases of the Ag-Si alloy, although it is a well-known simple binary eutectic alloy. Here, we show that the metastable phases composed of amorphous Si and supersaturated Ag solid solution are induced by the eutectic reaction under rapid cooling of Ag-Si. Furthermore, the solute Si in the Ag matrix reacts with oxygen to precipitate Ag by-products, which grow as nodules. The Ag nodules have high crystallinity and robust interfacial structures, and the nodule growth leads to the formation of cross-links between the Ag-Si particles. We also demonstrate the Ag nodule-mediated bonding where the rapidly cooled Ag-Si ribbon is directly used as a bonding medium, indicating the possibility of using it as a high-temperature bonding material with low-temperature processes.
亚稳相，如过饱和固溶体、过冷和非晶相，在冶金学中是众所周知的。它们通常处于非平衡状态，可以通过克服能量势垒并借助驱动力转变为稳定相。特别是，它已被广泛用于材料强化，过饱和固溶体的热处理主要诱导了固体中析出物的异质形核。然而，尽管Ag-Si合金是一种众所周知的简单二元共晶合金，但对其亚稳相却知之甚少。在此，我们表明，在Ag-Si快速冷却过程中，共晶反应会诱导出由非晶态Si和过饱和Ag固溶体组成的亚稳相。此外，Ag基体中的溶质Si与氧反应，沉淀出Ag副产物，这些副产物以结核的形式生长。Ag结核具有高结晶度和坚固的界面结构，结核的生长导致Ag-Si颗粒之间形成交联。我们还展示了Ag结核介导的键合，其中快速冷却的Ag-Si带材直接用作键合介质，这表明它有可能作为一种具有低温工艺的高温键合材料。
