The measurement of high phase-transition temperature is equally challenging and useful for developing high-temperature materials for critical applications. Pyrometer is a suitable option to measure the phase-transition temperature above 2300 K. In this work, Mo, Ta, and their isomorphous binary alloys are selected as the target system for high-speed pyrometer temperature measurements in the arc-melting setup. The present phase transitions (melting point, solidus, and liquidus) measurements indicate that the MoTa is an isomorphous system with a narrow freezing range (i.e., an average value < 35 K). The results from this present work would change the existing MoTa phase diagram. The Gibbs energy modeling for liquid (L) and BCC_A2 (α) phases of the MoTa system are then performed, including the latest experimental results from this work. The applications of the current experimental methodology could be extended to measure the high phase-transition temperatures in superalloys with significant commercial values.

高相变温度的测量同样具有挑战性，对于开发用于关键应用的高温材料非常有用。高温计是测量2300 K以上相变温度的合适选择。在这项工作中，选择Mo，Ta及其同构二元合金作为电弧熔化装置中高速高温计温度测量的目标系统。当前的相变（熔点，固相线和液相线）测量结果表明，Mo Ta是具有较窄冰点范围（即平均值<35 K）的同构系统。本工作的结果将改变现有的Mo Ta相图。Mo的液相（L）和BCC_A2（α）相的吉布斯能量模型然后执行Ta系统，包括这项工作的最新实验结果。当前实验方法的应用可以扩展到测量具有重要商业价值的高温合金中的高相变温度。