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采用XRD、OM、SEM和TEM对V-5Cr-5Ti合金铸态组织进行分析,研究第二相的行为。结果表明:采用真空电子束熔炼制备的V-5Cr-5Ti合金铸态组织具有粗大的晶粒,晶粒内部存在以层状第二相堆垛成树枝状为特征的成分偏析区;金属钒和铸态V-5Cr-5Ti合金的晶格常数分别为0.30316和0.30375 nm,V的单胞体积膨胀约0.58%;存在2种类型的第二相:(1)短条状第二相,具有fcc结构,晶格常数为0.4182~0.4228 nm;(2)椭圆状第二相,具有fcc结构,晶格常数为0.4186~0.4242 nm。V-5Cr-5Ti合金凝固过程中,首先Ti元素与C元素反应析出具有立方结构的亚稳间隙相(Ti_2C)或V元素与C元素反应析出具有hcp结构的亚稳间隙相(V_2C),随后原子发生相互取代,最终形成以Ti元素为主,V、Cr元素为辅,具有fcc结构的碳-氧-氮化物,化学式记为(Ti_2-CON)。
The as-cast microstructure of V-5Cr-5Ti alloy was analyzed by XRD, OM, SEM and TEM, and the behavior of the second phase was studied. The results show that the as-cast microstructure of V-5Cr-5Ti alloy prepared by vacuum electron beam melting has coarse grains and segregation of components characterized by delamination of dendritic second phase into dendrites; The lattice constants of the as-cast V-5Cr-5Ti alloy are 0.30316 and 0.30375 nm, respectively, and the unit cell volume of V expands by about 0.58%. There are two types of second phases: (1) a short second phase with fcc Structure with a lattice constant of 0.4182 ~ 0.4228 nm; (2) an elliptic second phase with an fcc structure with a lattice constant of 0.4186 ~ 0.4242 nm. During the solidification of V-5Cr-5Ti alloy, the metastable interstitial phase (V 2 C) with cubic structure and the metastable interstitial phase (V 2 C) with cubic structure were precipitated by the reaction between Ti and C, The atoms are replaced by each other to form a carbon-oxygen-nitride with a fcc structure, which is mainly composed of Ti and supplemented with V and Cr elements. The chemical formula is (Ti 2 -CON).