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采用Gleeble-3800热模拟试验机对20CrMnTiH钢进行了等温热压缩试验,研究了该钢在变形温度为850~1 150℃、应变速率为0.01~10 s~(-1)条件下的高温热变形行为,运用数学回归方法和热力学不可逆原理,建立了20CrMnTiH钢应变补偿的唯象本构方程和动态再结晶模型,并对该应变补偿的唯象本构模型进行了有效验证。在真应力-真应变曲线中,变形温度和应变速率对20CrMnTiH钢的流变应力影响显著,表现出正的应变速率敏感性和负的温度敏感性;由本构模型计算得到的流变应力值与试验值两者之间有很好的相关性(R=0.976 64),平均相对误差为5.544 2%;在应变硬化速率与流变应力关系曲线中,利用单一参数法和求解拐点法获得了不同变形条件下动态再结晶的临界应力σ_c和临界应变ε_c值,建立了临界应力、临界应变和Zener-Hollomon参数的数学模型ε≥ε_c=0.007 9 lnZ-0.153 23,且临界应变ε_c随着温度补偿应变速率因子Z的增加而增加。
The isothermal hot compression tests of 20CrMnTiH steel were carried out on a Gleeble-3800 thermal simulation machine. The hot deformation of the steel under the conditions of deformation temperature of 850 ~ 1 150 ℃ and strain rate of 0.01 ~ 10 s ~ (-1) The deformation constitutive equation and dynamic recrystallization model of strain compensation of 20CrMnTiH steel were established by using mathematical regression method and thermodynamic irreversible principle. The phenomenological constitutive model of strain compensation was validated. In the true stress-true strain curve, the deformation temperature and strain rate have a significant effect on the flow stress of 20CrMnTiH steel, showing positive strain rate sensitivity and negative temperature sensitivity. The calculated values of the flow stress (R = 0.976 64), and the average relative error is 5.544 2%. In the curve of strain hardening rate and flow stress, using the single parameter method and the inflection point method Under the condition of different deformation, the critical stress σ_c and critical strain ε_c of dynamic recrystallization, the critical stress, critical strain and Zener-Hollomon parameter ε ≥ ε_c = 0.007 9 lnZ-0.153 23, and the critical strain ε_c with the temperature The compensation strain rate factor Z increases.