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采用XRD、SEM和XRD对Nb-35Ti-4C合金热处理前后的相组成、界面结构、组织演变及力学行为进行研究。结果表明:热处理前后合金均由Nbss和(Nb,Ti)C构成。热处理过程中Nbss内部析出长条状的二次(Nb,Ti)C;(Nb,Ti)C内则析出长条状的二次Nbss。二次Nbss依附于fcc(Nb,Ti)C的密排面(111)面形核,与母相(Nb,Ti)C满足(N-W)位相关系:[011]_((Nb,Ti)C)//[001]_(Nbss), (111)_((Nb,Ti)C)//(110)_(Nbss)。碳化物与Nbss具有洁净良好的界面结合。热处理后单相(Nb,Ti)C变为(Nb,Ti)C+二次Nbss的共析组织。纳米压痕测试表明共析组织转变降低了碳化物的脆性,提高了合金的韧性。
The phase composition, interface structure, microstructure evolution and mechanical behavior of Nb-35Ti-4C alloy before and after heat treatment were investigated by XRD, SEM and XRD. The results show that the alloy before and after heat treatment consists of Nbss and (Nb, Ti) C. During the heat treatment, long secondary barium (Nb, Ti) C precipitates inside Nbss and long barrous Nbss precipitates within (Nb, Ti) C. The secondary Nbss is attached to the close-packed (111) plane nuclei of fcc (Nb, Ti) C and has a relationship with the (NW, Nb) phase of the parent phase ) // [001] _ (Nbss), (111) _ ((Nb, Ti) C) // (110) _ (Nbss). Carbides and Nbss have a clean, well-integrated interface. After heat treatment, single phase (Nb, Ti) C becomes eutectoid structure of (Nb, Ti) C + secondary Nbss. Nanoindentation tests show that the transformation of eutectoid structure reduces the brittleness of carbides and improves the toughness of the alloy.