析出强化与孪晶强化在Fe--24 Mn--3 Si--3 Al TWIP钢退火过程中的作用机制

对Fe-24Mn-3Si-3Al TWIP钢在不同退火工艺下进行力学性能测试,采用扫描电子显微镜(SEM)、能谱仪(EDS)和透射电子显微镜(TEM)观察钢的微观组织形貌.结果表明:随着退火温度和保温时间的变化,TWIP钢的力学性能并不符合常规的单调上升或下降的规律,而在退火温度为800℃、保温10 min和退火温度为900℃、保温20 min时发生波动.退火温度为800℃、保温10min条件下,钢的主要强化机制为析出强化,析出相(Fe,Mn)23C6的增多导致屈服和抗拉强度升高;退火温度为900℃、保温20 min条件下,钢中的析出相并未有明显的变化,而二次孪晶的产生及孪晶相互交割成为抗拉强度增加的主导因素.

Mechanism of precipitation strengthing and twinning strengthing in annealing process of Fe--24 Mn--3 Si--3 Al TWIP steel

The mechanical properties and strengthening mechanism of Fe-24Mn- 3Si- 3Al TWIP steels were investigated as a function of annealing process. The microstructures of the samples were analyzed by transmission electron microscopy, scanning electron microscopy, energy disperse spectroscopy. The experimental results indicate that as the annealing temperature and the holding time change, the mechanical properties of TWIP steel do not rise or fall monotonously, as would be conventionally. The mechanical proper-ties change in the annealing processes of annealing temperature 800℃ for 10 min and 900℃ for 20 min. The strengthening mechanism is mainly dispersion strengthening in the case of annealing process of 800℃ annealing temperature for 10 min, and an increase in the precipitation of ( Fe, Mn) 23 C6 leads to better mechanical properties. However, in the case of annealing process of 900℃ for 20 min, the precipitation of ( Fe, Mn) 23 C6 does not change obviously, but many twinning systems are initiated and secondary twin and twin de-livery are observed, which result in an increase in the ultimate tensile strength.