Phase transition kinetics in spheroidal graphite irons.

We plan to measure in-situ liquid-solid and solid-solid phase transitions in Fe-Si-C-alloys in the proposed experiment. One objective is to determine the undercooling for γ-Fe and graphite nucleation as a function of alloy composition and inoculation by ceramic microparticles, previously evaluated in SEM and TEM (see Figure 1). Also, the kinetics of the eutectic and eutectoid transitions will be recorded at fixed cooling rates as a function of crystallographic change: amorphous to γ-Fe in the eutectic (~1150 °C), and γ-Fe to α-Fe (~800 °C) in the eutectoid.

本拟开展的实验计划对铁硅碳（Fe-Si-C）合金中的原位液固及固固相变进行测量。实验的目标之一为确定γ铁（γ-Fe）与石墨形核的过冷度随合金成分以及陶瓷微粒孕育处理的变化关系，相关评估此前已通过扫描电子显微镜（SEM）与透射电子显微镜（TEM）完成（见图1）。此外，实验还将在固定冷却速率下，记录共晶与共析转变的动力学过程，该动力学随晶体学变化而呈现差异：共晶转变（约1150℃）对应非晶相向γ铁的转变，共析转变（约800℃）对应γ铁向α铁的转变。