Mingtao WANG
,
B.Y.Zong
,
Gang WANG
材料科学技术（英）
A model has been established to simulate the realistic spatio-temporal microstructure evolution in recrystallization of a magnesium alloy using the phase field approach. A set of rules have been proposed to decide the real physical value of all parameters in the model. The thermodynamic software THERMOCALC is applied to determine the local chemical free energy and strain energy, which is added to the free energy density of grains before recrystallization. The Arrhenius formula is used to describe boundary mobility and the activity energy is suggested with a value of zinc segregation energy at the boundary. However, the mobility constant in the formula was found out by fitting to a group of grain size measurements during recrystallization of the alloy. The boundary range is suggested to decide the gradient parameters in addition of fitting to the experimental boundary energy value. These parameter values can be regarded as a database for other similar simulations and the fitting rules can also be applied to build up databases for any other alloy systems. The simulated results show a good agreement with reported experimental measurement of the alloy at the temperatures from 300 to 400℃ for up to 100 min but not at 250℃. This implies a mechanism variation in activity energy of the boundary mobility in the alloy at low temperature.
关键词:
Static recrystallization
,
null
,
null
,
null
XIE Zhi-xiong
,
GAO Hai-yan
,
WANG Jun
,
YU Yan
,
FANG Yuan
,
SUN Bao-de
钢铁研究学报(英文版)
The static recrystallization kinetics of low-carbon steel cast strip was investigated by means of interrupted hot tensile tests. As-cast strip was reheated and soaked and its austenite grain size was similar to the width level of the as-cast columnar structure. The tests were carried out on Gleeble-3500 thermomechanical simulator. The deformation temperature is in the range of 800 to 1200 ℃ with strain rate of 001 to 1 s-1. The prestrain is fixed at 004 to 012, and the inter-hit delay time varies from 1 to 3000 s. Effect of deformation conditions and initial microstructure on static recrystallization behavior was investigated. The activation energy (Qsrx) and Avrami exponent (n) of static recrystallization were determined to have 241 kJ/mol and 054 respectively by linear regression of the experimental results. A kinetics model was proposed to describe the static recrystallization kinetics in low-carbon steel cast strip. The predicted softening fractions are in good agreement with the experimental results, indicating that the proposed equations can give an accurate estimate of the softening behaviors for the low-carbon steel cast strip.
关键词:
Static recrystallization
Jie HUANG
,
Zhou XU
,
Xin XING
材料科学技术（英）
Static recrystallization behavior of austenite for micro-alloyed steel during hot rolling was studied and the influence (т-εdiagram) of holding time and deformation at different deformations and isothermal temperatures on microstructural state of austenite were discussed. Corresponding to parameter Z in the dynamic recrystallization diagram, parameter Y was then introduced to simplify static recrystallization diagrams.
关键词:
Micro-alloyed steel
,
null
,
null
王健
,
肖宏
,
张志国
金属学报
在Gleeble--3500热力学模拟实验机上对Q235A钢试样进行单道次和双道次热压缩实验,
获得流变应力曲线. 把静态再结晶体积分数看作是时间的函数,
将其与热变形结束后位错密度的变化联系起来. 通过
对热压缩实验获得的流变应力曲线的逆分析,
提出了确定静态再结晶动力学模型的新方法. 它可以取代
传统的通过对淬火微观组织金相分析来估算静态再结晶动力学的方法.
运用此方法于普碳钢的热压缩实验中,
在一定的形变量范围内获得了静态再结晶动力学方程. 与已有的模型作比较,
本文提出的方法仅
需少量实验和计算即可获得准确的静态再结晶动力学模型.
关键词:
静态再结晶
,
flow curves
,
hot compression
