The evolution of the dislocation densities in martensite and in austenite during the quench of a low-carbon (0.215 wt% C) steel is investigated in situ by the mean of a High Energy X-Ray Diffraction experiment on a synchrotron beamline. The line configuration offers an excellent time resolution well adapted to the studied martensitic transformation kinetics. The mean density of dislocations in martensite increases as the transformation proceeds confirming that dislocations are not homogeneously distributed between the laths in agreement with some recent post-mortem observations. The resulting spatial distribution of dislocations and the associated strain-hardening support the views assuming that lath martensite is a heterogeneous microstructure and behaves as a “multiphase” aggregate. In austenite, the increase in dislocation densities is even more significant meaning that austenite in martensite is also a hard phase, contradicting some recent theories attributing to films of retained austenite a major role in the plasticity of martensite.

通过在同步辐射束线上进行高能X射线衍射实验，对低碳（0.215 wt％C）钢淬火过程中马氏体和奥氏体中位错密度的变化进行了原位研究。管线配置提供了出色的时间分辨率，非常适合于研究的马氏体转变动力学。随着相变的进行，马氏体中位错的平均密度增加，这证实了位错在板条之间不是均匀分布的，这与一些最近的验尸观察一致。假定板条马氏体是一种非均质的微观结构并且表现为“多相”聚集体，由此产生的位错空间分布和相关的应变硬化支持了上述观点。在奥氏体中