Precipitation in a CrCr2Nb alloy
Precipitation in a CrCr2Nb alloy
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DOI：
10.1016/s1359-6454(97)00050-5
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发表时间：
1997-09
期刊：
影响因子：
9.4
通讯作者：
K. Kumar;C. Liu
中科院分区：
文献类型：
--
作者：
K. Kumar;C. Liu
研究了含12 at. %的Nb进行了检查，在铸态和退火条件下，使用光学和电子显微镜技术。在铸态条件下，Cr固溶体基体和Cr固溶体与C15 Cr2 Nb的共晶混合物共存。在Cr基体中，邻近Cr/Cr2 Nb界面，观察到位错，并且可能是两相之间的热失配的结果。远离共晶Cr2 Nb的基体固溶体也表现出高位错密度和强烈的变形带，没有发生Cr2 Nb在基体中的固态析出。然而，在1200°C下退火短至3小时后，发生沉淀;这些具有C15晶体结构的沉淀物具有具有六边形横截面和小面的端盖的棒状形态。这些沉淀物是孪晶的，孪晶系统与共晶Cr2 Nb中的相同。在沉淀物/基体界面处观察到失配位错，并且在与沉淀物/基体界面相邻的Cr基体中也存在由热收缩失配引起的位错。沉淀物-基体取向关系为（101）m//（11）p和[101]m//101] p。在1200°C下暴露较长时间导致一些沉淀物粗化。偶尔观察到第二种类型的沉淀物，其具有与基体的立方对立方取向和11.5 A的晶格参数，在延长退火后持续存在，并且被鉴定为M6 C型碳化物（M = Cr，Nb），其可以通过其他间隙污染物（例如氧）来稳定。
The microstructure of a CrCr2Nb two-phase alloy containing 12 at. % Nb was examined in the as-cast and annealed conditions using optical and electron microscopy techniques. In the as-cast condition, a Cr solid-solution matrix and a eutectic mixture of Cr solid solution and C15 Cr2Nb coexist. In the Cr matrix, adjacent to the CrCr2Nb interface, dislocations are observed and are likely a consequence of the thermal mismatch between the two phases. The matrix solid solution, away from the eutectic Cr2Nb, also exhibits a high dislocation density and intense deformation bands; no solid-state precipitation of Cr2Nb in the matrix had occurred. Upon annealing for as little as 3 h at 1200°C, however, precipitation occurs; these precipitates, with the C15 crystal structure, have a rod morphology with a hexagonal cross-section and faceted end-caps. These precipitates are twinned, the twinning system being the same as in the eutectic Cr2Nb. Mismatch dislocations are observed in the precipitate/matrix interface and dislocations arising from thermal contraction mismatch are also present in the Cr matrix adjacent to the precipitate/matrix interface. The precipitate-matrix orientation relationship was (101)m//(11 )pand [1 01]m//1 01]p. Exposure at 1200°C for extended times results in some precipitate coarsening. A second type of precipitate with a cube-on-cube orientation with the matrix and a lattice parameter of a ≅ 11.5 A ̊ was occasionally observed, persisted upon extended annealing, and was identified as an M6C-type carbide (M = Cr, Nb) that may be stabilized by other interstitial contaminants such as oxygen.