Spheroidal graphite is the defining microstructural feature of ductile iron and also plays an important role in compacted graphite iron. It is widely accepted that graphite spheroids are engulfed by austenite at an early stage of solidification after which their growth is impeded by the slow diffusion of carbon through a layer of austenite. In this work, a compacted graphite iron-containing spheroidal graphite was studied after interruption of its solidification by water quenching. Selected areas of a cross section of the castings were investigated using quantitative electron probe microanalysis, with emphasis on the distribution of carbon in austenite. The measured carbon concentration near graphite was generally below the theoretical carbon concentration in austenite at equilibrium with graphite at 1140 °C. Numerical simulations of diffusion of carbon in austenite around spheroidal graphite suggest that a zone of austenite around graphite was likely depleted of carbon during quenching, possibly explaining the low measured concentrations. The measured carbon concentration near graphite varied by as much as 0.3 wt%, with the lowest concentrations consistently found in the central region of compacted graphite–austenite eutectic cells. Regardless of whether these differences were present prior to quenching or are consequences thereof, they seem to reflect either departures from, or displacements of, the carbon concentration in austenite at equilibrium with graphite. This indicates that there is something about growth of graphite embedded in austenite which is not well understood. Concentrations of Si, Mn and Cu are near equal in the compared regions and do not explain the observed differences in carbon content near graphite.

中文翻译：

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电子探针显微分析法研究水淬压实石墨铁上奥氏体中碳的分布

球墨铸铁是球墨铸铁的定义性显微组织特征，在压实石墨铁中也起着重要作用。广泛接受的是，石墨球体在凝固的早期就被奥氏体所吞没，此后由于碳缓慢扩散通过奥氏体层而阻碍了它们的生长。在这项工作中，经过水淬淬火后，研究了一种压实的含铁的球形石墨。使用定量电子探针显微分析研究了铸件横截面的选定区域，重点是碳在奥氏体中的分布。在1140°C时，与石墨平衡时，在石墨附近测得的碳浓度通常低于奥氏体中的理论碳浓度。碳在球形石墨周围奥氏体中扩散的数值模拟表明，淬火过程中石墨周围的奥氏体区域可能会耗尽碳，这可能解释了测得的低浓度。在石墨附近测得的碳浓度变化幅度最大为0.3 wt％，在压缩的石墨-奥氏体共晶电池的中心区域始终发现最低的碳浓度。不管这些差异是在淬火之前存在还是其后果，它们似乎都反映出在与石墨平衡时奥氏体中碳浓度的偏离或位移。这表明埋藏在奥氏体中的石墨的生长尚不清楚。硅的浓度