低碳钢形变诱导相变组织在冷却过程中的晶粒长大

通过热模拟实验考察了低碳钢在略高于Ar3温度变形时发生形变诱导铁素体相变(DIFT)的组织演变规律;探讨了变形后连续冷却以及在不同温度下保温对DIFT组织的影响·结果表明,DIFT组织含量随变形量的增大而增多,但在较大的变形量下仍然有部分奥氏体没有发生DIFT;在随后的冷却过程中,未转变奥氏体通过静态相变形成粗大的铁素体,与形变诱导铁素体组织一起形成混晶组织·DIFT铁素体晶粒在形变后冷却过程中发生长大现象·实验测定和理论计算结果都表明,在连续冷却条件下,形变诱导组织存在晶粒长大终止温度,当温度低于该温度时DIFT晶粒停止长大;在不同温度等温时,也存在DIFT晶粒稳定的温度上限,在低于该温度保...

DIFT Grain Growth in Low Carbon Steel During Cooling

The evolution process of DIFT (deformation induced ferrite transformation) microstructure in low carbon steel at the temperature slightly higher than A_(r3) as well as the effect of subsequent continuous cooling/holding process at different temperatures on DIFT microstructure was investigated using thermo-simulator. The experimental results showed that although the volume fraction of DIFT microstructure increases with increasing true strain, such an increase hasn't found in a part of austenite even after a heavy deformation. The deformed austenite is transformed into coarse ferrite in a static transformation mode during the subsequent cooling, thus forming a mixed crystal microstructure. Both the experimental and theoretical calculation results confirm that, during the continuous cooling after deformation, there is a critical temperature below which the grain growth in DIFT microstructure will stop. During the holding at different temperatures after deformation, the grain growth will become very slow when the holding temperature is lower than a certain temperature.