Phase Transformation of Dynamically Recrystallized Austenite

研究了纯碳钢、IF钢和镍合金钢动态再结晶（DRX）基体中发生的静态回复和再结晶及其对奥氏体-铁素体相变的影响。主要研究结果如下：1.动态再结晶基体中发生的静态回复过程除经典的静态回复和再结晶外，还有变晶回复和再结晶。动态再结晶基体在退火条件下的静态软化曲线显示出三个阶段，并且在较长的退火时间内不会达到完全软化。结果表明，动态再结晶晶粒结构在高温下可以稳定存在.动态再结晶晶粒分为动态晶核、含有位错密度梯度的生长动态再结晶晶粒和含有均匀分布位错亚结构的较粗动态再结晶晶粒。动态再结晶晶粒的长大导致了动态再结晶基体发生软化和不完全软化三个阶段.碳含量的增加使普碳钢动态再结晶奥氏体的静态软化开始加速，而不完全软化则随碳含量的增加而增加. IF钢中的动态再结晶奥氏体晶粒细化导致铁素体晶粒细化。动态再结晶奥氏体经长时间退火后，铁素体晶粒几乎不长大。这是由于动态再结晶基体中稳定存在生长晶粒的结果.与普通基体相比，动态再结晶基体中马氏体转变迅速，转变后的组织更加细化。

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.