塑性应变和时效处理对碳锰钢组织结构的影响

EFFECT OF PLASTIC STRAIN AND AGING TREATMENT ON MICROSTRUCTURE OF CARBON-MANGANESE STEELS

在引入少量的塑性变形的基础上,对碳锰钢进行了200℃、40min的时效处理。研究了应变以及时效前后的组织结构变化。研究结果表明,组织为多数铁素体和少量珠光体组成,铁素体呈板条形状,在铁素体板条上有Mn_(23)C_6存在。析出物形状有圆形以及短棒形,尺寸为纳米级。预拉伸变形导致材料中的位错密度增加,位错组态为稀疏的位错结构,并发现了析出物与位错的交互作用现象。分析认为,200℃时效导致C原子在位错线附近形成Cottrell气团,钉扎位错运动,从而提高了材料屈服强度。

Following small plastic strains, a carbon-manganese steel was ageing at 200℃ for 40 minuets and then the change in microstrncture of the aged steels before and after ageing was investigated. Research results indicate that the microstructure of the carbon-manganese steel consists of a large number of ferrite （F） and a small number of pearlite （P）. The ferrite is lathy in shape, on which there are precipitates of Mn23C6. All the precipitates are nanosized and some of them are round, some are short-bar-shaped. The pretension deformation results in an increased dislocation density, and the dislocations distribute sparsely in the steel. The interaction between dislocations and precipitates was also found. It is concluded that the ageing at 200℃ results in the generation of Cottrell atmosphere of carbon atoms around dislocation lines and hence the motion of dislocations is pinned, so that the yield strength of the steel is increased.