【摘要】 用真空电弧熔炼方法制备了处于共晶区的Nb-18Si复合材料,用背散射电子相(BEI)和X射线衍射(XRD)分析了铸态和1 200℃×100h退火后复合材料的微观组织形貌和相组成,并进行了断口形貌分析。结果发现退火可以促进亚稳定相Nb3Si分解成Nb5Si3+Nb。延性相Nbss粒子尺寸和体积分数的增加影响材料的断口形貌,铸态的断口完全呈解理断裂,退火以后断口中出现界面脱离。脆性相对延性相的约束程度对材料的韧性影响很大。更多还原

【Abstract】 Nb-based in-situ composites at eutectic compositions were prepared by arc-melting in vacuum,followed by heat treatment at 1 200℃ for 100 hours.The microstructure and composition of the sample were investigated using scanning electron microscopy（SEM） with back-scattered electron image（BEI）,energy disperse spectrum（EDS） and X-ray diffraction（XRD）.The fracture surface was analyzed for comparing the fracture toughness of annealed sample to that of as-cast sample.The results reveal that heat treatment results in a phase transformation,Nb₃Si→Nb₅Si₃+Nb_ss.The change of fractography depends on the volume fraction and size of ductile phase Nb_ss,where Nb_ss denotes Nb solid solution.The as-cast sample failed by cleavage fracture.In annealed sample,decohesion is seen at the interface of Nb_ss and silicide.Ductile phase is constrained by brittle matrix and high constraint plays an important role to damage fracture toughness of composites.更多还原