Q&P980超高强钢的循环加载性能和微观组织表征
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摘要
为研究超高强钢的循环加载性能,以淬火配分(quenching&partitioning,Q&P)980超高强钢为研究对象,通过循环次数、循环位置以及各向异性的拉伸实验,得到真实应力应变曲线,分析卸载环的性质,对其力学性能进行准确表征,再通过金相显微镜、X射线衍射(X-ray diffraction,XRD)等检测手段,分析相应的微观组织变化。发现随着形变程度的增加,卸载和重新加载斜率不断降低,回弹应变、延伸率和强度不断增加,相应的奥氏体含量不断下降,即具有相变诱导塑性(transformation induced plasticity,TRIP)效应。当变形程度相近时,随着循环次数的增加,回弹应变不是持续增加,而是在循环次数增加到10时出现回弹应变减小的情况。循环加载过程会减弱板材的各向异性,但是对弹性模量和回弹的影响不大。
The true stress-strain curve for ultra-high strength steel Q&P980 is obtained through cyclic loading of the ultra-high strength steel in terms of the number of cycles,cyclic position and anisotropy of the cyclic tensile test.The properties of the unloading ring were also analyzed to accurately characterize the mechanical properties.A metallographic microscope using X-ray diffraction(XRD)was then used to study the microstructural changes.The results show that increasing the deformation reduced the slope of the unloading and reloading curves.In addition,reducing the austenite content increased the springback strain,elongation and strength,which is called the transformation induced plasticity(TRIP)effect.For similar amounts of deformation,increasing the number of cycles did not increase the springback strain but reduce it when the cycle number increased to 10.The cyclic loading weakens the sheet anisotropy,but has little effect on the elastic modulus and springback.
The true stress-strain curve for ultra-high strength steel Q&P980 is obtained through cyclic loading of the ultra-high strength steel in terms of the number of cycles,cyclic position and anisotropy of the cyclic tensile test.The properties of the unloading ring were also analyzed to accurately characterize the mechanical properties.A metallographic microscope using X-ray diffraction(XRD)was then used to study the microstructural changes.The results show that increasing the deformation reduced the slope of the unloading and reloading curves.In addition,reducing the austenite content increased the springback strain,elongation and strength,which is called the transformation induced plasticity(TRIP)effect.For similar amounts of deformation,increasing the number of cycles did not increase the springback strain but reduce it when the cycle number increased to 10.The cyclic loading weakens the sheet anisotropy,but has little effect on the elastic modulus and springback.
引文
[1]朱国明,康永林,朱帅.汽车用超高强Q&P钢的工艺与组织性能研究[J].机械工程学报,2017,53(12):110-117.ZHU G M,KANG Y L,ZHU S.Study on process,microstructure and property of ultra-high strength Q&P steel for automobile[J].Journal of Mechanical Engineering,2017,53(12):110-117.(in Chinese)
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[8]于婷.汽车用高强塑第三代薄板钢非弹性回复行为的研究[D].长春:吉林大学,2015.YU T.Research on inelastic recovery behavior of the third generation automobile sheet steels presenting with ultrahigh strength and high ductility[D].Changchun:Jilin University,2015.(in Chinese)
[9]KIM H,KIM C,BARLAT F,et al.Nonlinear elastic behaviors of low and high strength steels in unloading and reloading[J].Materials Science and Engineering:A,2013,562:161-171.
[10]PAVLINA E J,LIN C J,MENDIGUREN J,et al.Effects of microstructure on the variation of the unloading behavior of DP780 steels[J].Journal of Materials Engineering and Performance,2015,24(10):3737-3745.
[11]LEE J Y,LEE M G,BARLAT F,et al.Piecewise linear approximation of nonlinear unloading-reloading behaviors using a multi-surface approach[J].International Journal of Plasticity,2017,93:112-136.
[12]YOSHIDA F,UEMORI T.A model of large-strain cyclic plasticity describing the Bauschinger effect and workhardening stagnation[J].International Journal of Plasticity,2002,18(5-6):661-686.
[13]ANDAR M O,KUWABARA T,YONEMURA S,et al.Elastic-plastic and inelastic characteristics of high strength steel sheets under biaxial loading and unloading[J].ISIJ International,2010,50(4):613-619.
[14]徐虹,刘亚楠,于婷,等.双相钢DP780在循环加载-卸载过程中的非弹性回复行为及其微观机理[J].吉林大学学报:工学版,2017,47(1):191-198.XU H,LIU Y N,YU T,et al.Inelastic recovery behavior and microscopic mechanism of high strength DP780 steel during cyclic loading-unloading[J].Journal of Jilin University(Engineering and Technology Edition),2017,47(1):191-198.(in Chinese)
[2]江海涛,唐荻,米振莉,等.配分工艺对低碳Q&P钢中残余奥氏体的影响[J].材料科学与工艺,2011,19(1):99-103.JIANG H T,TANG D,MI Z L,et al.Effect of partitioning parameters on the retained austenite in low-carbon Q&P Steel[J].Materials Science and Technology,2011,19(1):99-103.(in Chinese)
[3]蒯振,陈银莉,赵爱民,等.低碳Si-Mn系Q&P钢不同配分时间的热处理工艺[J].金属热处理,2012,37(11):95-99.KUAI Z,CHEN Y L,ZHAO A M,et al.Heat treatment process of low carbon Si-Mn Q&P steel with different partitioning time[J].Heat Treatment of Metals,2012,37(11):95-99.(in Chinese)
[4]孙珊珊.卸载循环对Q&P980钢微观组织影响的研究[D].长春:吉林大学,2016.SUN S S,Study on the effect of unloading cycle on microstructure of Q&P980 steel[D].Changchun:Jilin University,2016.(in Chinese)
[5]丁磊,林建平,庞政,等.考虑TRIP效应的Q&P980超高强度钢多相本构模型[J].塑性工程学报,2013,20(4):23-26.DING L,LIN J P,PANG Z,et al.Multiphase constitutive model of ultra-high strength steel Q&P980coupling with TRIP effect[J].Journal of Plasticity Engineering,2013,20(4):23-26.(in Chinese)
[6]何忠平,何燕霖,高毅,等.低硅无铝中碳TRIP钢中残留奥氏体的机械稳定性[J].材料热处理学报,2011,32(s1):44-47,51.HE Z P,HE Y L,GAO Y,et al.Mechanical stability of retained austenite in low-silicon,non-aluminum and medium-carbon TRIP steels[J].Transactions of Materials and Heat Treatment,2011,32(s1):44-47,51.(in Chinese)
[7]余海燕,陈关龙,李淑慧,等.不同应变方式下TRIP钢中残余奥氏体的体积分数随应变量的变化[J].钢铁研究学报,2005,17(2):48-51,78.YU H Y,CHEN G L,LI S H,et al.Change of volume fraction of austenite with strain in TRIP steel[J].Journal of Iron and Steel Research,2005,17(2):48-51,78.(in Chinese)
[8]于婷.汽车用高强塑第三代薄板钢非弹性回复行为的研究[D].长春:吉林大学,2015.YU T.Research on inelastic recovery behavior of the third generation automobile sheet steels presenting with ultrahigh strength and high ductility[D].Changchun:Jilin University,2015.(in Chinese)
[9]KIM H,KIM C,BARLAT F,et al.Nonlinear elastic behaviors of low and high strength steels in unloading and reloading[J].Materials Science and Engineering:A,2013,562:161-171.
[10]PAVLINA E J,LIN C J,MENDIGUREN J,et al.Effects of microstructure on the variation of the unloading behavior of DP780 steels[J].Journal of Materials Engineering and Performance,2015,24(10):3737-3745.
[11]LEE J Y,LEE M G,BARLAT F,et al.Piecewise linear approximation of nonlinear unloading-reloading behaviors using a multi-surface approach[J].International Journal of Plasticity,2017,93:112-136.
[12]YOSHIDA F,UEMORI T.A model of large-strain cyclic plasticity describing the Bauschinger effect and workhardening stagnation[J].International Journal of Plasticity,2002,18(5-6):661-686.
[13]ANDAR M O,KUWABARA T,YONEMURA S,et al.Elastic-plastic and inelastic characteristics of high strength steel sheets under biaxial loading and unloading[J].ISIJ International,2010,50(4):613-619.
[14]徐虹,刘亚楠,于婷,等.双相钢DP780在循环加载-卸载过程中的非弹性回复行为及其微观机理[J].吉林大学学报:工学版,2017,47(1):191-198.XU H,LIU Y N,YU T,et al.Inelastic recovery behavior and microscopic mechanism of high strength DP780 steel during cyclic loading-unloading[J].Journal of Jilin University(Engineering and Technology Edition),2017,47(1):191-198.(in Chinese)