将Nb-V微合金钢在1200 ℃固溶0.5 h后淬火, 然后在450 ℃回火4 h, 结合扫描电子显微镜(SEM)和透射电子显微镜(TEM), 用三维原子探针(3DAP)研究渗碳体内部和渗碳体/基体界面处的元素分布和成分变化. 结果显示, 淬火样品中C原子由于自回火而出现轻微偏聚, 其它合金原子V,Nb, Si, Mn, Mo和Al等分布均匀. 450 ℃回火4 h样品中出现C原子偏聚区, 在该区域内, Mn含量较高, Mo和V轻微偏聚, Si和Al很少, 对应渗碳体析出, Si富集在渗碳体/基体界面处; 另外, 观察到C和V明显偏聚的单原子面, 周围富集Si和Mn, 对应合金碳化物析出初期形成的G.P.区, 成分主要为V4C3.
Three dimensional atom probe (3DAP) combined with SEM and TEM was applied to characterize the alloying elements partitioning segregation in cementite in experimental steel tempering at 450℃ for 4h after solution treatment at 1200℃ for 0.5h. The results indicated that, in the as-quenched specimen nearly all the alloying elements such as manganese, silicon and vanadium were dissolved in matrix with homogeneous distribution, and a slight segregation of carbon for the sake of autotempering. A significant segregated zone of carbon found in the 450℃ tempering specimen was detected as a cementite, in which was there an enrichment of manganese, a slight segregation of molybdenum and vanadium and negligible aluminum content, silicon was prone to partitioning at cementite/matrix interface from cementite. A monolayer in thickness enriched with carbon and vanadium was also detected, which may be a V4C3 based G.P. zone acted as an initiator of precipitation of alloyed carbides during an intensity or extensive tempering.
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