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利用Gleeble热模拟实验机、Vickers硬度计、SEM,HRTEM及DSC研究了淬火态含Nb和Nb-Mo微合金钢在升温过程中碳化物的析出行为.利用经典形核长大理论及Avrami方程对淬火态钢中MC型碳化物的析出动力学进行了计算.结果表明,含Nb和Nb-Mo微合金钢淬火后以20℃/min的速率加热至不同温度水冷,在300和700℃,由于e-碳化物和MC型碳化物析出而出现了硬度峰值.MC型碳化物在650℃左右析出,由于析出强化而硬度上升,与理论计算得到的MC型碳化物的析出鼻子点温度约650℃的结果相一致.Mo进入Nb C中降低了Nb C与铁素体基体的错配度,从而减小了析出相与铁素体基体间的界面能,使得(Nb,Mo)C析出动力学加快,所以Nb-Mo钢中析出相粒子分布更为密集,尺寸更为细小,具有较高的析出强化作用.
The precipitation behavior of carbides in quenched Nb and Nb-Mo microalloyed steel during heating was studied by Gleeble thermal simulator, Vickers hardness tester, SEM, HRTEM and DSC. By using classical nucleation and growth theory and Avrami equation The results show that the microalloyed Nb and Nb-Mo microalloyed steel is quenched at a rate of 20 ℃ / min and then cooled to different temperatures. At 300 and 700 ℃, carbide and MC type carbide precipitated the hardness peak appeared.MC type carbide precipitation at about 650 ℃, due to precipitation strengthening and hardness increased, with the theoretical MC carbide precipitation nose temperature of about 650 ℃ .Mo entry into NbC decreases the mismatch between NbC and ferrite matrix, which reduces the interfacial energy between the precipitated phase and the ferrite matrix, resulting in (Nb, Mo) C precipitation kinetics Therefore, the precipitated phase particles in Nb-Mo steels are more densely distributed and the size is smaller and have higher precipitation strengthening effect.