铁素体晶粒尺寸对铁素体—马氏体双相钢DP980动态变形行为影响

Effects of Ferrite Grain Size on Dynamic Deformation Behavior of Ferrite-martensite Dual Phase Steel DP980

为了研究铁素体晶粒尺寸对铁素体—马氏体冷轧双相钢DP980动态变形行为的影响,通过连续退火试验,得到两组马氏体体积分数相同、而铁素体晶粒尺寸不同的试样。选取应变速度为1×10-4s-1和1×10-2s-1进行准静态拉伸试验;选取应变速度为500 s-1、1 000 s-1和1 750 s-1在分离式霍普金森拉杆(Split Hopkinson tensile bar,SHTB)上进行动态拉伸试验。使用不考虑晶粒尺寸影响的Johnson-Cook(J-C)率相关模型和考虑晶粒尺寸影响的修正的Khan-Huang-Liang(KHL)率相关模型分析双相钢的动态变形行为,并引入可决系数R2来判定试验结果与模型的吻合关系。分析结果得出修正的KHL模型与试验结果吻合较好,其可决系数R2达到了0.998 7,表明修正的KHL模型可以很好地描述DP980材料在低应变速度和高应变速度下的变形行为,能够反映铁素体晶粒尺寸对DP980动态变形行为的影响。

Effects of ferrite grain size on quasi-static and dynamic deformation behavior of ferrite-martensite dual phase steel（DP980） are investigated.Two groups of experimental dual phase DP steels with the same martensite volume fraction and different ferrite grain size are obtained through performing the experiment with different austenitizing temperature.The quasi-static tensile experiment and the dynamic tensile experiment for the two groups of DP steels are carried out at strain rates ranging from 10-4 to 1 750 s-1 at room temperature using universal testing machine CMT4105 and split Hopkinson tensile bar（SHTB）,respectively.Then the true stress-effective plastic strain curves of DP980 steel for five strain rates have been obtained through the data processing.Johnson-Cook（J-C） model,which is not concerned with effects of grain size,and modified Khan,Huang and Liang（KHL） model,which is concerned with effects of grain size,are used to research dynamic deformation behavior of dual phase steel.And coefficient of determination R2 is introduced to determine goodness of fit for experimental results and models.The analysis results of the experiment indicate that modified KHL model is in good agreement with the experimental results,whose R2 reaches 0.998 7,and that modified KHL model has good characterization of deformation behavior for DP980 over a wide range of strain rates,and can reflect effects of grain size on dynamic deformation behavior of DP980.