双相钢中残余奥氏体对性能的影响及其热稳定化

用声发射法研究了一种低合金钢于双相区热处理所得残余奥氏体的马氏体相变。发现残余奥氏体的热稳定化程度和稳定性均与奥氏体的颗粒尺寸有关。颗粒愈小，热稳定化程度愈高，且愈稳定。不存在马氏体核胚的极小奥氏体颗粒不能仅靠过冷来使其转变。形变能诱发试验钢中残余奥氏体转变，且增加钢的塑性。但只有奥氏体颗粒尺寸有合适的分布，其中小部分稳定性很高，才能使马氏体相变随应变增加而逐渐发生并延伸到大的应变，使延伸率明显增加。

The Effects of Retained Austenite on the Ductility of Dual-phase Steels and its Thermostabilization

The martensitic transformation of retained austenite particles in an intercritically annealed low-alloy steel has been studied using the acoustic emission technique.It was found that both the stability and the thermostabilization of austenite particles were dependent on the particle size and carbon content. The particle size thermostabilization effect is interpreted as a increasing efficiency of utilizing carbon atoms to anchor martensitic embryos in a particle with decreasing particle volume. And the particle size stabilization effect is viewed as a decreasing probability of finding dislocations in a particle with decreasing particle volume. Those austenite particles which do not contain martensite embryos will not transform by suporcooling alone. Plastic deformation can bring about the transformation by introducing dislocations in the austenite particles. The transformation of the retained austenite particles is shown to enhance the ductility of the tested steels.However,only if the retained austenite particles have a suitable distribution of stabilities,so that their transformations can gradually occur as increasing strain and extend to larger Strain, then the enhanced ductility will be obvious.