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计算得到低碳马氏体形成时使残余奥氏体富碳所需扩散的时间约为7×10~(-3)—3×10~(-4)s。与条状马氏体形成的时间——10~(-3)—10~(-6)s比较,可见碳的扩散跟得上或稍落后于马氏体条的形成。残余奥氏体均匀富碳的时间落后于马氏体条的形成至少达1个数量级。这些表明低碳马氏体形成时可能存在碳的扩散,但后者不是马氏体相变的主要或必需过程。若低碳马氏体按上贝氏体形式长大,则计算所得其长大速率仅3×10~(-4)cm/s,比现有实验数据至少低2个数量级。本文工作再次证明低碳马氏体的形成机制和上贝氏体的不同。
The time required for carbon enrichment of retained austenite in the formation of low-carbon martensite is about 7 × 10 -3 -3 × 10 -4 s. Compared with the formation time of martensite - 10 ~ (-3) -10 ~ (-6) s, the diffusion of carbon follows or slightly lags behind the formation of martensite. The time for the retained austenite to become carbon-rich lags behind the formation of martensite at least an order of magnitude. These indicate that there may be carbon diffusion in the formation of low-carbon martensite, but the latter is not the main or necessary process of martensitic transformation. If low-carbon martensite grows in the form of upper bainite, the calculated growth rate is only 3 × 10 -4 cm / s, which is at least 2 orders of magnitude lower than the existing experimental data. The work of this paper proves once again that the formation mechanism of low carbon martensite is different from that of upper bainite.