In Situ Calorimetry Study on Cooling of the Metallic-Glass Forming Melts

Optimizing the microchannel design of the next generation of chips requires an understanding of the in situ property evolution of the chip-based materials under fast cooling. This work overcomes the conventional reliance on reheating data of melt-quenched glasses by demonstrating direct observations of glass transition on cooling curves utilizing the most advanced fast differential scanning calorimetry. By leveraging an MEMS chip sensor that allows for rapid heat extraction from microgram-sized samples to a purged gas coolant, the device is able to reach ultra-fast cooling rates of up to 40,000 K·s^-1. Four thermal regions are identified by examining the cooling behaviors of two metallic glasses. This is because the actual rate of the specimen can differ from the programmed rate, especially at high set rate when the actual rate decreases before the glass transition is completed. We define the operational window for reliable cooling curve analysis, build models with empirical and theoretical analyses to determine the maximum feasible cooling rate, and demonstrate how optimizing sample mass and environment temperature broaden this window. The method avoids deceptive structural relaxation effects verified by fictivetemperature analysis and permits the capture of full glass transition during cooling.