Abstract Crystallization of metallic glasses produced by rapid solidification and supercooled liquids on heating takes place at large undercooling which has some peculiarities compared to crystallization on casting. By using transmission electron microscopy we present a detailed in-situ study of an unusual isothermal crystallization reaction observed in the Al85Y8Ni5Co2 metallic glassy alloy below Tg. It started from the formation of a primary intermetallic compound (IMC) immediately followed by a pseudo-eutectic reaction consisting of IMC and nanoscale Al (solid solution) particles while α-Al particles are significantly smaller in size than the intermetallic phase. Moreover, a majority of these nanoscale α-Al particles do not have a common interface with the primary IMC particles but are separated by the residual glassy phase which remains present within these pseudo-eutectic colonies. On the other hand, as can be assumed from the Gaussian type of the heat flow plot at the isothermal conditions and reasonable linearity of the Avrami plot this reaction takes place like a single stage process. This residual glassy phase has a high stability versus crystallization and crystallizes only at a higher temperature. However, such a crystallization mechanism is observed only on slow heating or isothermal exposure at a temperature below Tg. On rapid heating or at isothermal annealing in the supercooled liquid, primary nanocrystallization of the aluminum solid solution is observed followed by the formation of intermetallic compounds at a higher temperature.

中文翻译：

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在不同加热速率下在 TEM 中原位观察到的 Al 85 Y 8 Ni 5 Co 2 金属玻璃的异常结晶

摘要 快速凝固和过冷液体加热产生的金属玻璃的结晶发生在大过冷度下，这与铸造结晶相比具有一些特点。通过使用透射电子显微镜，我们对在低于 Tg 的 Al85Y8Ni5Co2 金属玻璃合金中观察到的异常等温结晶反应进行了详细的原位研究。它开始于主要金属间化合物 (IMC) 的形成，紧接着是由 IMC 和纳米级 Al（固溶体）颗粒组成的假共晶反应，而 α-Al 颗粒的尺寸明显小于金属间相。而且，大多数这些纳米级 α-Al 颗粒与初级 IMC 颗粒没有共同的界面，而是被残留的玻璃相隔开，这些玻璃相仍然存在于这些假共晶群中。另一方面，从等温条件下的热流图的高斯类型和 Avrami 图的合理线性可以假设，该反应像单阶段过程一样发生。这种残留的玻璃相对于结晶具有高稳定性，并且仅在较高温度下结晶。然而，这种结晶机制仅在低于 Tg 的温度下缓慢加热或等温暴露时观察到。在过冷液体中快速加热或等温退火时，