Coarsening of nanoscale (Ti,Mo)C precipitates in different ferritic matrixes
Coarsening of nanoscale (Ti,Mo)C precipitates in different ferritic matrixes
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DOI：
10.1016/j.matchar.2018.05.034
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发表时间：
2018-08
影响因子：
4.7
通讯作者：
Lei Cheng;Q. Cai;Wei Yu;J. Lv;H. Miura
中科院分区：
文献类型：
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作者：
Lei Cheng;Q. Cai;Wei Yu;J. Lv;H. Miura
利用高分辨透射电镜和原位加热透射电镜研究了准多边形铁素体（QPF）基体和多边形铁素体（PF）基体中纳米级（Ti，Mo）C析出相的粗化过程。在不同形核过程的影响下，PF基体中直接观察到大团状析出相溶解和小相间析出相长大的逆粗化过程。然而，由于高密度亚晶界的演化，QPF基体中析出相的粗化主要表现为亚晶界迁移辅助粗化过程，在此过程中，亚晶界被扫过后形成拱形粗化析出相。原子结构分析表明，拱形粗化沉淀物的“镶嵌”是溶质原子从可动亚晶界向（Ti，Mo）C沉淀物的{111}密排面再沉淀形成的，而“钥匙石”则是由于再沉淀面向{200}的转变而形成的。几何相分析（GPA）表明，（Ti，Mo）C析出相周围的各向异性应变场不仅导致了拱形析出相形成过程中再析出方向的改变，而且还导致了PF基体中聚集析出相的选择性粗化。
Coarsening of nanoscale (Ti,Mo)C precipitates within quasi-polygonal ferritic (QPF) matrix and polygonal ferritic (PF) matrix is studied via HRTEM and In-situ heating TEM. Influenced by different nucleation processes, inverse coarsening process showing dissolution of large clustered precipitates and growth of small interphase precipitates is directly observed in the PF matrix. However, due to the evolution of high-density subboundaries, coarsening of precipitates in QPF matrix is mainly characterized by the subboundary migration assisted coarsening process, during which arch-like coarsened precipitates form after the sweeping of subboundaries. Analysis of atomic structure clarify that “imposts” of the arch-like coarsened precipitates are established by the re-precipitation of solute atoms from movable subboundary to the close packed planes {111} of (Ti,Mo)C precipitates, and that the “key stones” are constructed due to the change of re-precipitation planes to {200}. Geometric phase analysis (GPA) illustrates that not only the change of re-precipitation direction during the formation of arch-like precipitates, but also the selective coarsening of clustered precipitates in PF matrix, is caused by the highly anisotropic strain field around (Ti,Mo)C precipitates.