Mo-Si-B三元系中T2相的中高温变形行为

Mo5SiB2 (T2) undergoes a brittle-to-ductile transition at ~1000℃, which makes possible the use of this potential ultra-temperature structural material. More attentions will be focused on dislocation types, structures, mobility, interaction and their effects on the aspects of flow stress, yield phenomenon, work hardening and crack propagation, when the deformation tests are conducted in the temperature range of 1200-1700℃ and in the strain rate regime of 10-2-10-5s-1. Observations are achieved by SEM and AFM to reveal slip bands on the surfaces of compression samples, and by TEM to reveal the dislocations in deformed microstructures, with the purpose of studying the impacts of microstructure evolution on deformation behaviors under different conditions (temperature, strain rate, strain, etc.). The obtained advances in the theory of microscopic distortional mechanisms will be beneficial to the performance optimization of T2 and Mo-Si-B alloys, and even to develop the structural materials operative at high temperatures above 1200℃.

Mo5SiB2（T2）相在中温区（~1000℃）发生脆—韧转变，为其在超高温结构材料方面的应用提供了可能。本项目拟在系统考察T2相合金不同应变速率（10-2-10-5s-1）下中高温区（1200-1700℃）变形行为的基础上，着重研究位错组态、运动、反应等以及它们对流变应力、屈服现象、加工硬化能力、裂纹扩展等的影响。通过对不同温度压缩变形试样表面滑移带的SEM与AFM观察以及变形组织中位错的TEM观察，研究变形过程中的位错类型与组态及其随温度、应变速率、应变量的变化，以及这种变化对变形行为的影响，进而从基础层面揭示T2相合金中高温变形的微观机理，为Mo-Si-B三元系合金及T2相本身性能优化提供理论基础，对发展超高温（>1200℃）结构材料具有学术价值和重要意义。

Mo5SiB2 (T2）相脆-韧转变发生在较宽的温度范围内，1000℃为临界点，[010](001)等滑移系在外力的作用下开动，阻碍了裂纹进一步扩展， K1C值急剧增加。1200℃时，开动的独立滑移系增多，塑性变形能力及加工硬化能力增强。当温度增加到1400℃及以上时，攀移同滑移一样成为位错重要的运动方式，从而出现了{143}、{523}、{311}非密排面等。该项目从基础层面揭示T2相合金中高温变形的微观机理，为Mo-Si-B三元系合金及T2相本身性能优化提供理论基础，对发展超高温（>1200℃）结构材料具有学术价值和重要意义。