奥氏体转变温度以上变形时应变速率对低碳钢动态软化行为的影响

Effect of Strain Rate on Dynamic Softening Behavior of Low Carbon Steel during Deformation above Austenite Transformation Temperature

利用Gleeble-1500热模拟试验机,将一低碳微合金钢在Ac3温度以上(950℃)进行了4种不同的应变速率(10、7、3、1 s^(-1))的压缩变形,然后淬火处理。对高温变形的应力应变曲线用双微分法进行变换,发现材料变形过程中主要有两种软化机制,分别为动态相变和动态再结晶,随变形速率的增加,材料发生软化的两个临界应力呈线性升高的趋势;两个临界应变则随应变速率变化不大。用金相显微镜观察观察了材料淬火后的金相组织,发现材料内的Widmanstätten铁素体板条宽度随应变速率的增加而逐渐变细,多边形铁素体的数目随应变速率的增加而增加;Widmanstätten铁素体板条一般为平行或垂直关系,而垂直关系的Widmanstätten铁素体板条并不呈现严格的直角,而是偏离一定的角度。

Using a Gleeble-1500 thermal simulation testing machine,a low carbon microalloyed steel was subjected to compression deformation at 4 different strain rates(10,7,3,1s^(-1))above A_(c3) temperature(950℃),and then quenched.The stress-strain curve of high temperature deformation was transformed by the double differential method,and it is found that there are two main softening mechanisms in the process of material deformation,namely dynamic phase transformation and dynamic recrystallization.With the increase of deformation rate,the two critical stresses for material softening increase linearly.The two critical strains do not change much with the change of the strain rate.The metallographic structure of the material after quenching was observed with a metallographic microscope.It is found that the width of the Widmanstätten ferrite laths within the material decreases with strain rate increasing and the number of polygonal ferrites increases with strain rate increasing;Widmanstätten ferritic laths are generallyin a parallel or perpendicular relationship,while Widmanstätten ferritic laths in perpendicular relation do not present a strictly right angle,but rather deviate froma certain angle.