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Effect of Ti/V ratio on thermodynamics and kinetics of MC in γ/α matrices of Ti–V microalloyed steels
Journal of Iron and Steel Research International ( IF 3.1 ) Pub Date : 2021-02-22 , DOI: 10.1007/s42243-020-00539-1
Ke Zhang , Xin-jun Sun , Zhao-dong Li , Kun Xu , Tao Jia , Zheng-hai Zhu , Xiao-yu Ye , Jun-yu Kang , Qi-long Yong

Through the solubility product theory of the ternary secondary phase, classical nucleation theory, and Ostwald ripening theory, a model was established to describe the thermodynamics and kinetics of (Ti, V)C precipitates in austenite/ferrite (γ/α) matrices. The model was used to calculate the volume fraction, precipitation–temperature–time (PTT) curve, and nucleation rate–temperature (NrT) curve of MC (M = Ti, V) precipitates in γ/α matrices in Ti–V microalloyed steels with various Ti/V ratios, which is verified by hardness tester, transmission electron microscopy and energy-dispersive X-ray spectroscopy. The calculations indicate that, by decreasing Ti/V ratio from Ti4V0 steel to Ti0V4 steel, the complete-dissolution temperature decreases monotonically from 1226 to 830 °C, and the equilibrium volume fraction of MC precipitated from austenite decreases from 0.333% to 0.091% at 900 °C. Moreover, the maximum nucleation temperature of MC precipitated from α matrix decreases from 748 to 605 °C and the fastest precipitation temperature decreases from 844 to 675 °C as Ti/V ratio decreases. PTT and NrT diagrams of MC precipitated from α matrices in different Ti–V microalloyed steels all exhibit C-shaped and inverse C-shaped curves. In addition, both theoretical calculation and experimental results show that when tempered at 600 °C for 100 h, Ti2V2 steel shows the largest hardness value of 312 HV among the three steels tested because it has a larger volume fraction (0.364%), a larger precipitate density (1689 μm−2), and the smallest average size (8.4 nm) of (Ti, V)C precipitates. The theoretical calculations are consistent with experimental results, which indicates that the thermodynamics and kinetics model for (Ti, V)C precipitates is reliable and accurate.



中文翻译:

Ti / V比对Ti-V微合金钢γ/α基体中MC的热力学和动力学的影响

通过三元二次相的溶解度乘积理论,经典成核理论和奥斯特瓦尔德熟化理论,建立了一个模型来描述奥氏体/铁素体(γ/α)基质中(Ti,V)C沉淀的热力学和动力学。该模型用于计算Ti–V微合金钢在γ/α基体中的MC(M = Ti,V)析出物的体积分数,沉淀-温度-时间(PTT)曲线和成核速率-温度(NrT)曲线具有各种Ti / V比,并已通过硬度测试仪,透射电子显微镜和能量色散X射线光谱仪进行了验证。计算结果表明,通过将Ti / V比从Ti4V0钢降低到Ti0V4钢,完全溶解温度从1226降至830°C,900℃时,奥氏体析出的MC的平衡体积分数从0.333%降低到0.091%。此外,随着Ti / V比的降低,从α基体中析出的MC的最大成核温度从748降低到605°C,最快的析出温度从844降低到675°C。在不同的Ti–V微合金钢中,从α基体析出的MC的PTT和NrT图均显示出C形和反C形曲线。此外,理论计算和实验结果均表明,在600℃下回火100 h时,Ti2V2钢在三种测试钢中均显示出312 HV的最大硬度值,因为它具有更大的体积分数(0.364%),更大的体积分数。沉淀物密度(1689μm 随着Ti / V比的降低,从α基体中析出的MC的最大成核温度从748降低到605°C,最快的析出温度从844降低到675°C。从不同Ti–V微合金钢中的α基质析出的MC的PTT和NrT图均显示出C形和C形逆曲线。此外,理论计算和实验结果均表明,在600℃下回火100 h时,Ti2V2钢在三种测试钢中表现出最大的312 HV硬度值,因为它具有更大的体积分数(0.364%),更大的体积分数。沉淀物密度(1689μm 随着Ti / V比的降低,从α基体中析出的MC的最大成核温度从748降低到605°C,最快的析出温度从844降低到675°C。从不同Ti–V微合金钢中的α基质析出的MC的PTT和NrT图均显示出C形和C形逆曲线。此外,理论计算和实验结果均表明,在600℃下回火100 h时,Ti2V2钢在三种测试钢中均显示出312 HV的最大硬度值,因为它具有更大的体积分数(0.364%),更大的体积分数。沉淀物密度(1689μm 从不同Ti–V微合金钢中的α基质析出的MC的PTT和NrT图均显示出C形和反C形曲线。此外,理论计算和实验结果均表明,在600℃下回火100 h时,Ti2V2钢在三种测试钢中均显示出312 HV的最大硬度值,因为它具有更大的体积分数(0.364%),更大的体积分数。沉淀物密度(1689μm 从不同Ti–V微合金钢中的α基质析出的MC的PTT和NrT图均显示出C形和C形逆曲线。此外,理论计算和实验结果均表明,在600℃下回火100 h时,Ti2V2钢在三种测试钢中均显示出312 HV的最大硬度值,因为它具有更大的体积分数(0.364%),更大的体积分数。沉淀物密度(1689μm-2),并且沉淀出最小的(Ti,V)C平均尺寸(8.4 nm)。理论计算与实验结果吻合,表明(Ti,V)C沉淀物的热力学和动力学模型是可靠和准确的。

更新日期:2021-02-22
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