AISI 4340钢马氏体相变的研究

采用膨胀法对AISI 4340钢在900~1 150℃几种不同温度下进行奥氏体化,以得到不同的奥氏体晶粒度(AGS),然后快速冷却到室温,得到马氏体组织.实验结果表明:奥氏体晶粒度和晶界析出相对马氏体相变动力学,尤其是马氏体转变温度(tms)产生很大影响.总的趋势是AGS越大,tms越高.在不同的奥氏体化温度段,会有不同的C,N化合物析出,对马氏体形核产生影响.在奥氏体化温度低于1 000℃时,AGS增大,tms快速增加.其原因主要是由于AlN等晶界析出相对马氏体形核的促进作用.在奥氏体化温度高于1 050℃时,tms随AGS增大而升高,这是因为TiC等溶解温度较高的化合物在晶界析出对马氏体形...

On the Martensite Transformation Kinetics of AISI 4340 Steel

By means of thermal dilatation a AISI 4340 steel was austenitized at some different temperatures in a range from 900 to 1150°C to obtain different austenite grain sizes (AGS), then rapidly cooled to room temperature to obtain martensitic structures. The transmission electron microscopy (TEM) including electron diffraction and microanalysis was used to describe the microstructures. It was found that both AGS and A1N exert a great effect on the martensite transformation kinetics. The larger the AGS, the higher the starting temperature of martensite transformation (tms). Within different austenitizing temperature ranges, there are different kinds of compound precipitates found, affecting the nucleation of martensites. At and below 1000°C, since the particles of AlN play an important role during the martensite transformation, tms increased rapidly. However at and above 1050°C, tms still increases with AGS. This fact may be due to the precipitation of relatively higher dissolution temperature, such as TiC, on the boundary of austenite.