Kolli R Prakash, Seidman David N
1Department of Materials Science and Engineering,Northwestern University,Evanston,IL 60208,USA.
Microsc Microanal. 2014 Dec;20(6):1727-39. doi: 10.1017/S1431927614013221. Epub 2014 Sep 25.
The composition of co-precipitated and collocated NbC carbide precipitates, Fe3C iron carbide (cementite), and Cu-rich precipitates are studied experimentally by atom-probe tomography (APT). The Cu-rich precipitates located at a grain boundary (GB) are also studied. The APT results for the carbides are supplemented with computational thermodynamics predictions of composition at thermodynamic equilibrium. Two types of NbC carbide precipitates are distinguished based on their stoichiometric ratio and size. The Cu-rich precipitates at the periphery of the iron carbide and at the GB are larger than those distributed in the α-Fe (body-centered cubic) matrix, which is attributed to short-circuit diffusion of Cu along the GB. Manganese segregation is not observed at the heterophase interfaces of the Cu-rich precipitates that are located at the periphery of the iron carbide or at the GB, which is unlike those located at the edge of the NbC carbide precipitates or distributed in the α-Fe matrix. This suggests the presence of two populations of NiAl-type (B2 structure) phases at the heterophase interfaces in multicomponent Fe-Cu steels.
通过原子探针断层扫描（APT）实验研究了共沉淀和并置的NbC碳化物析出物、Fe3C渗碳体（碳化铁）以及富铜析出物的成分。还研究了位于晶界（GB）处的富铜析出物。碳化物的APT结果辅以热力学平衡时成分的计算热力学预测。基于化学计量比和尺寸区分出两种类型的NbC碳化物析出物。位于碳化铁周边和晶界处的富铜析出物比分布在α-Fe（体心立方）基体中的富铜析出物更大，这归因于铜沿晶界的短路扩散。在位于碳化铁周边或晶界处的富铜析出物的异相界面处未观察到锰偏析，这与位于NbC碳化物析出物边缘或分布在α-Fe基体中的富铜析出物不同。这表明在多组分Fe-Cu钢的异相界面处存在两种NiAl型（B2结构）相。
