Ti-V复合低碳钢在回火过程中MC型碳化物的析出与强化行为

Precipitation and strengthening behaviors of MC type carbides in a Ti-V low carbon steel during tempering process

利用维氏硬度计、OM(光学显微镜)、EBSD(电子背散射衍射)和TEM(透射电子显微镜)对在600℃回火不同时间后的Ti-V复合微合金化马氏体钢的维氏硬度、微观组织及析出相随回火时间的演变进行了研究。结果表明:随回火时间的增长,实验钢的硬度变化为先下降后上升再下降。前期由于位错密度降低,引起实验钢硬度下降。回火开始后,由于析出相的沉淀强化作用,硬度逐渐上升,并在回火1 h时达到峰值。回火1 h后,析出相开始粗化并引起位错密度降低,实验钢的硬度又开始下降,并在100 h时达到最低值。在回火过程中析出相的形状和尺寸都发生了明显变化。在回火1 h时实验钢的主要强化机制为沉淀强化,沉淀强化增量占总强度的34.9%,而在回火100 h时沉淀强化仍是钢中的主要强化方式。

The changes in Vickers hardness, microstructure and precipitates with time of tempering at 600 ℃ of a Ti-V microalloyed martensitic steel were studied by using Vickers hardmeter, OM, EBSD and TEM. The results show that with the increase of tempering time the hardness decreases first, then increases gradually to a peak value at 1 h and decreases subsequently. The decrease of hardness in the beginning is owing to the decrease of dislocation density. when tempering begins, MC phase begins to precipitate. Due to its precipitation strengthening, the hardness raises and reaches the maximum when tempering for 1 h. After that, because of precipitates coarsening and recovery of matrix microstructure, the hardness drops again and reaches the minimum when tempering for 100 h. The changes of shapes and sizes of MC phases during tempering are obvious. Precipitation strengthening is the dominant strengthening mechanism and contributes 34.9% of total yield strength when tempering for 1 h. The dominant strengthening mechanism is also precipitation strengthening when tempering for 100 h.