中文摘要：

采用压缩和单边缺口三点弯曲实验,研究了Mo5SiB2 （T2相）合金试样在真空条件和不同温度下的压缩行为和断裂行为,利用XRD, SEM－EDS和TEM等对试样变形后的微观组织、位错组态和断口形貌进行了分析和观察.结果表明, T2相的脆－韧转变温度为1000－1200℃.在外加切应力的作用下, [010]（001）和〈110〉{110}等多个滑移系开始开动,导致试样发生明显的塑性变形. 由于刃型位错比螺型位错或混合型位错活跃,表现为[010]刃型位错深入到滑移面{110}, 与〈110〉位错发生交互作用,形成大量位错节点, 导致加工硬化. 随温度升高,试样断裂模式从单一解理断裂向穿晶解理－沿晶混合断裂转变,在1000℃时, 试样断口处能清晰地观察到滑移带.

英文摘要：

The ordered intermetallic Mo5SiB2 （T2 phase） is a promising elevated-temperature structural material because of its high melting temperature, and excellent resistance to oxidation and creep. T2 phase has a body-centered tetragonal D81 structure （I4/mcm）,with 20 Mo, 4 Si and 8 B atoms situating in layered arrangements along the c axis.This structure has been regarded as the obstacle to plastic deformation or dislocation activity especially at ambient temperature. However, like most intermetallic compounds, it undergoes a brittle-to-ductile transition （BDT） up to high temperatures, where the increased ductility is companied by microstructure changes. The feature of high-temperature applications makes it necessary to investigate the BDT behavior. The analysis of microstructure, dislocation configuration and fracture surfaces were carried out by compression and three-point bending tests, coupled with XRD, SEM-EDS and TEM methods. The result suggested that BDT happened over a wide temperature range of 1000-1200℃. At the BDT temperature above, multiple slip systems such as the [010]（001） and 〈110〉{110} could be activated under an applied stress, resulting in obvious plastic deformation. Since the edge dislocation displayed more activity than screw and mixed ones, the edge dislocation with b=[010] interacted with the 〈110〉-type dislocation via slipping into its plane of {110}. Therefore, the work hardening was caused by the formation of lots of dislocation nodal points during the subsequent compression process. With temperature increasing, the fracture mode underwent a conversion from transgranular cleavage at ambient temperature to a mix of transgranular cleavage and intergranular failure.