中碳25Mn钢低温韧化机制

Toughening mechanism of medium carbon 25Mn cryogenic steel

为研究中碳25Mn钢的低温韧化机制,测定了其在不同温度下的冲击功,观察了冲击断口处的显微组织,并采用EBSD技术对组织中各相的构成及晶界组成进行了分析,进而讨论了实验钢在不同温度下的变形机制及其对韧性的影响,结果表明:室温时裂纹尖端区域主要通过TWIP机制实现韧化;随温度降低,裂纹尖端区域中的TRIP机制增强,这虽然能够缓解尖端的应力集中,但生成的马氏体会促进裂纹扩展,导致韧性降低;结果也证明,低温下断口附近的变形机制既有孪生也有滑移,位错的滑移易于诱发“slipping-off”机制,这也会导致钢的韧性恶化。总体来看,实验钢的低温韧性主要取决于裂纹尖端较小范围内材料的变形机制,而TRIP机制的韧化效果低于TWIP机制。

In order to study the low-temperature toughening mechanism of medium carbon 25 Mn steel, the impact energy of this steel at different temperatures was measured, and the deformation mechanism and its effects on toughness of tested steel was discussed by the observing of microstructure, analyzing the composition of phases and grain boundaries in the microstructure near fracture. The results show that at room temperature, the crack tip region is toughened mainly by TWIP mechanism. With the decreasing of temperature, TRIP mechanism is enhanced. Although the stress concentration at crack tip can be alleviated, the martensite obtained promotes the crack growth. Moreover, the deformation mechanism near the fracture includes both twinning and slipping, and the slipping of dislocation is easy to induce the "slipping off" mechanism, which also makes the toughness of the steel deteriorate. Totally, the low temperature toughness of the tested steel mainly depends on the deformation mechanism within a small range of the crack tip, and the toughening effect of TRIP mechanism is lower than that of TWIP mechanism.