Phase Transformation of Dynamically Recrystallized Austenite

研究了动态再结晶（DRX）基体的静态恢复和再结晶及其对奥氏体向铁素体相变的影响。主要研究结果总结如下：在DRX基体中发生的静态恢复过程包括元动态恢复和再结晶以及经典的静态恢复和再结晶。DRX基体在退火条件下的静态软化曲线表现为三步走，在较长的退火时间内不会达到完全软化。结果表明，DRX晶粒结构在高温下可以稳定存在。DRX颗粒可分为以下几类：动态核，生长的含有位错密度梯度的DRX晶粒和含有均匀分布的位错亚结构的较粗的DRX晶粒。DRX晶粒的生长导致DRX基体发生三步软化和不完全软化。3 .随着碳含量的增加，普通碳钢DRX奥氏体的静态软化开始加速，而不完全软化值则随着碳含量的增加而增加。中频钢中较细的DRX奥氏体晶粒导致较细的铁素体晶粒的演化。DRX奥氏体经过长时间退火后，铁素体晶粒几乎不长大。这是由于生长的晶粒在DRX基体中稳定存在的结果。与普通基体相比，DRX基体的马氏体转变速度快，转变的显微组织更精细。

Static recovery and recrystallization taking place in dynamically recrystallized (DRX) matrices and the effect of them on the austenite to ferrite phase transformation were studied by using plain carbon, IF (interstitial free) and nickel alloy steels. The main results are summarized as follows.1. Static restoration processes taking place in DRX matrices are metadynamic recovery and recrystallization as well as classical static recovery and recrystallization. The static softening curves under annealing of DRX matrices indicate three steps and do not go to full softening for a long period of annealing time. It is concluded that DRX grain structures can exist stably at high temperatures.2. DRX grains are classified into the following categories ; dynamic nuclei, growing DRX grains which contain a dislocation density gradient and coarser DRX grains containing a uniformly distributed dislocation substructures. The growing DRX grains results in the three steps of softening and incomplete softening taking place in DRX matrices.3. Static softening in DRX austenite of plain carbon steels is accerated initially by increasing of carbon content and, in contrast, the values of incomplete softening increase with carbon content.4. Finer DRX austenite grains in IF steels lead to the evolution of finer ferrite grains compared with usual grains. Ferrite grains scarcely grow even after annealing of DRX austenite for a long period of time. These results from the stable existence of growing grains in DRX matrices.5. Martensite transformation takes place rapidly and the microstructures transformed are more refined in DRX matrices compared with those in usual matrices.