Mo-Si-B三元系中T2相的脆-韧转变行为  

BRITTLE-TO-DUCTILE TRANSITION FOR T2 IN THE Mo-Si-B SYSTEM

作　　者：潘昆明[1] 张来启[1] 王礞[1] 林均品[1] 

机构地区：[1]北京科技大学新金属材料国家重点实验室,北京100083

出　　处：《金属学报》2013年第11期1392-1398,共7页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目50871012;国家重点基础研究发展计划项目2011CB605502资助~~

摘　　要：采用压缩和单边缺口三点弯曲实验,研究了Mo_5SiB_2(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.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.

关 键 词：Mo_5SiB_2(T2相) 压缩变形 断裂 位错组态 脆-韧转变 

分 类 号：TG146.4[一般工业技术—材料科学与工程]