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金属学报  2018, Vol. 54 Issue (6): 859-867    DOI: 10.11900/0412.1961.2017.00315
  本期目录 | 过刊浏览 |
退火温度对冷轧7Mn钢拉伸行为的影响及模拟研究
阳锋1, 罗海文2, 董瀚3()
1 钢铁研究总院 北京 100081
2 北京科技大学冶金与生态工程学院 北京 100083
3 上海大学材料科学与工程学院 上海 200072
Effects of Intercritical Annealing Temperature on the Tensile Behavior of Cold Rolled 7Mn Steel and the Constitutive Modeling
Feng YANG1, Haiwen LUO2, Han DONG3()
1 Central Iron and Steel Research Institute, Beijing 100081, China
2 School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China
3 School of Materials Science and Engineering, Shanghai University, Shanghai 200072, China
全文: PDF(3259 KB)   HTML
摘要: 

利用EBSD、TEM和XRD等手段研究了退火温度对冷轧中锰钢7%Mn-0.3%C-2%Al (质量分数)组织和力学性能的影响,并借助具物理冶金意义的本构模型探讨了冷轧中锰钢退火后的拉伸和加工硬化行为。实验结果表明,随着退火温度的上升,逆转变奥氏体的机械稳定性逐渐降低,使得应变诱导马氏体的转变速率快速上升。在700 ℃退火时,逆转变奥氏体的稳定性适中,此时材料的综合力学性能最优。模拟结果表明,奥氏体稳定性对材料的拉伸行为有决定性的影响。退火温度偏低则奥氏体稳定性过高,材料的加工硬化率和均匀延伸率都较低;若退火温度适中则奥氏体稳定性也适中,变形时能持续地产生TRIP效应硬化基体,使材料的加工硬化率和均匀延伸率均较高;退火温度偏高会导致奥氏体稳定性过低,应变诱导马氏体会在短期内大量形成,致使材料的抗拉强度较高但均匀延伸率降低。

关键词 中锰钢奥氏体稳定性相变诱导塑性效应    
Abstract

Medium Mn steel is composed of sub-micron grained ferrite and austenite, the unstable austenite may transform to martensite during plastic straining. Although the mechanical properties of medium Mn steel could be easily tested by tensile test, it is quite difficult to directly measure the influences of different constituent phases on the tensile and work hardening behavior. Thus, at the present work, EBSD, TEM, XRD and a constitutive model based on dislocation density have been used to study the effects of intercritical annealing (IA) temperature on the tensile properties and work hardening behavior of a newly designed medium Mn steel, Fe-7%Mn-0.3%C-2%Al (mass fraction). Experimental results showed that with the increase of IA temperature, the mechanic stability of reverted austenite decreased gradually and the kinetics of strain induced martensite rose rapidly. The stability of the reverted austenite was moderate when intercritically annealed at 700 ℃, this led to the best plasticity and the optimal mechanical properties. Simulated results exhibited that the mechanic stability of austenite has a decisive influence on the tensile behavior of the material. The austenite stability will be too high if the IA temperature is lower, and this will lead to the lower work hardening rate and uniform elongation; when the IA temperature is moderate, the stability of austenite will be optimum, consequently strain-induced martensite would be progressively produced during straining and result in the higher work hardening rate and prolonged uniform elongation; the stability of austenite will be too lower if the IA temperature is higher, thus larger volume fraction of strain-induced martensite would be formed in a short period, and this would result in the higher tensile strength but the inferior uniform elongation.

Key wordsmedium Mn steel    austenite stability    TRIP effect
收稿日期: 2017-07-25     
ZTFLH:  TG335.5  
基金资助:国家自然科学基金项目No.U1460203
作者简介:

作者简介 阳 锋,男,1983年生,博士生

引用本文:

阳锋, 罗海文, 董瀚. 退火温度对冷轧7Mn钢拉伸行为的影响及模拟研究[J]. 金属学报, 2018, 54(6): 859-867.
Feng YANG, Haiwen LUO, Han DONG. Effects of Intercritical Annealing Temperature on the Tensile Behavior of Cold Rolled 7Mn Steel and the Constitutive Modeling. Acta Metall Sin, 2018, 54(6): 859-867.

链接本文:

https://www.ams.org.cn/CN/10.11900/0412.1961.2017.00315      或      https://www.ams.org.cn/CN/Y2018/V54/I6/859

图1  S680、S700和S720的EBSD像
图2  S680、S700和 S720的TEM像
Sample Size / μm α β n
Ferrite Austenite
S680 0.91 0.42 4.0 5.5 7.0
S700 0.99 0.60 4.0 6.0 7.0
S720 0.73 0.62 4.7 7.0 3.5
表1  铁素体和奥氏体晶粒尺寸及应变诱导马氏体动力学的相关参数
图3  不同温度退火后马氏体体积分数随应变量的变化[16]及拟合曲线
图4  冷轧7Mn钢经不同温度退火后的真应力-真应变曲线
图5  S700在真应变为0.095和0.35时的TEM像
Phase G GPa b
nm
α M K
MPaμm1/2
ρ0 / m-2 k1 k2 dc
μm
S680 S700 S720 S680 S700 S720 S680 S700 S720
Ferrite 81.6 0.25 0.38 2.95 120 9×1013 3×1013 1×1013 0.004+
0.03VM
0.004+
0.03VM
0.0035+
0.03VM
1.3 1.3 1.5 1.6
Austenite 72.0 0.25 0.35 2.95 420 9×1013 3×1013 1×1013 0.045+
0.01VM
0.05+
0.01VM
0.05+
0.02VM
0.8 0.6 0.6 1.6
Martensite 81.6 0.25 0.38 2.95 - 1×1015 1×1015 1×1015 0.04 0.04 0.05 1.0 1.0 1.0 0.3
表2  室温下冷轧7Mn钢中各相的材料参数及拟合系数
图6  奥氏体位错密度的实测值[16]与模拟值
图7  实测与计算的真应力-真应变曲线及加工硬化率(WHR)曲线
图8  S680~S720总的及各组成相的真应力-真应变曲线和加工硬化率曲线的计算值
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