新型奥氏体热作模具钢6Mn14Cr3Mo2V2的强韧化机制

Mechanism of Strength-Toughness of a New Austenitic Hot Die Steel 6Mn14Cr3Mo2V2

通过OM、SEM与TEM分析新型奥氏体热作模具钢6Mn14Cr3Mo2V2的微观组织,利用电解法萃取6Mn14Cr3Mo2V2在退火、固溶及时效状态下的碳化物,通过XRD对其进行物相分析,并与Thermo-Calc热力学相图计算结果进行比较。研究表明:钢中组织为单相奥氏体+碳化物,在时效状态下,钢中碳化物含量约为4.59%,碳化物类型为VC,与Thermo-Calc计算结果基本符合。根据上述结果提出6Mn14Cr3Mo2V2强韧化机制:时效态下,铬与钼元素不形成碳化物,固溶在奥氏体中起固溶强化作用;钢中主要强化相为时效过程中弥散析出的粒径10 nm左右的VC,而固溶过程中未溶的较大体积的VC钉扎在奥氏体基体上,阻碍晶粒长大,起细化晶粒作用。

The microstructure of a new austenitic hot die steel 6Mn14Cr3Mo2V2 was studied by means of OM,SEM and TEM.The carbides in the steel under three different states（i.e.annealed,solutionized and aged） were gained by the method of electro-extraction and then analyzed by XRD.The results show that the structure of 6Mn14Cr3Mo2V2 is composed of the single austenite and carbides.After aging,it is found that the content of carbides in the steel is about 4.59%.The results of XRD phase analysis show that almost all of the carbides are VC.And the results simulated by thermo-calc are in agreement with experiments.Based on the above results,the mechanism of strength-toughness is proposed： Cr and Mo dissolve into austenite and form few carbides,so they play a role of solution strengthening.On the other hand,as the precipitation strengthening plays the main strengthening mechanism in the austenitic steel,dispersed VC with the size in 10nm precipitate during the aging process.Meanwhile,the undissolved bigger VC pin up at austenite matrix impeding the growth of grains and playing a role of refinement of austenite grains.