Nb-Ti微合金高强钢动态再结晶动力学及临界条件  

Kinetics and Critical Conditions for Initiation of Dynamic Recrystallization of Nb-Ti Microalloyed High Strength Steel

作　　者：张永集 吴光亮[1] 武尚文 ZHANG Yongji;WU Guangliang;WU Shangwen(School of Minerals Processing and Bioengineering,Central South University,Changsha 410083)

机构地区：[1]中南大学资源加工与生物工程学院,长沙410083

出　　处：《材料导报》2018年第22期3900-3907,共8页Materials Reports

基　　金：国家自然科学基金(51661130154)

摘　　要：在Gleeble-3500热模拟试验机上对Nb-Ti微合金高强钢进行了热模拟压缩试验,研究了其在变形温度为900～1 100℃、应变速率为0.01～5s^(-1)、最大变形量为70%条件下的动态再结晶行为。对流变曲线的分析及微观组织观察结果表明,低温高应变速率下流变曲线未显现出典型动态再结晶特征,但此条件下已发生动态再结晶。使用双曲正弦形Arrhenius关系计算的Nb-Ti微合金钢变形激活能为404kJ/mol。利用加工硬化原理和Cingara-McQueen模型确定了动态再结晶初始临界应力和应变,分析了由Cingara-McQueen模型计算临界应力值偏高的原因,建立了临界应力、应变和Z参数之间的定量关系,得到了动态再结晶临界应力和应变方程:σ_c=0.335Z0.144,ε_c=0.005 9Z^(0.079)。通过对θ-ε曲线进行分析,建立了最大软化速率处应变(ε_m)和变形条件的关系。在此基础上使用Avrami型动态再结晶动力学模型计算了不同变形条件下的再结晶体积分数,结果表明此模型可准确预测Nb-Ti微合金高强钢动力学。The hot compression test was conducted on a Gleeble-3500 thermo-simulation machine over the range of temperatures from 900 ℃ to 1 100 ℃ and strain rates from 0.01 s -1 to 5 s -1 to study the dynamic recrystallization behavior of Nb-Ti microalloyed steel. The analysis of flow curve and the microstructure observation showed that the flow curve does not show the typical dynamic recrystallization characteristic, but the dynamic recrystallization has occurred under the condition of high temperature and low strain rate. The Arrhenius model of flow curves was used to calculate the deformation activation energy. The critical stress and strain were determined by using the method of work hardening and a constitutive equation. The reason for the high modeled values for critical stress was analyzed, and the quantitative relationship between the critical stress, strain and Z parameter was established so that the critical conditions equations of dynamic recrystallization were obtained： σ c=0.335 Z 0.144 , ε c=0.005 9 Z 0.079 . The relationship between the strain at maximum softening rate and the deformation conditions was established by analyzing the θ-ε curves. Furthermore, the volume fraction of dynamic recrystallization was calculated based on these critical values and the results showed that the model has a good agreement with the data directly obtained from the flow curves.

关 键 词：NB-TI微合金钢 动态再结晶 临界应变 最大软化速率 

分 类 号：TG142.1[一般工业技术—材料科学与工程]