中文摘要：

在DIL805A/T热模拟试验机上对20CrNi2Mo板条马氏体钢进行了等温单道次轴向热压缩试验,结合光学显微镜（OM）、扫描电镜（SEM）、电子背散射衍射（EBSD）和显微硬度计,研究了形变量对20CrNi2Mo钢板条马氏体组织演变规律和力学性能的影响。结果表明：20CrNi2Mo钢在压缩变形过程中极易发生动态再结晶,动态再结晶开始的临界应变为0.22。当变形量小于临界应变时,原奥氏体晶粒尺寸变化不大,板条束尺寸增加,板条块宽度减小,小角度晶界所占比例逐渐增大,大角度晶界所占比例逐渐减少;当变形超过临界应变后,随着变形量的增加,原奥氏体晶粒、板条束、板条块逐渐被细化,小角度晶界所占比例先略有减小后逐渐增大。极图分析表明,20CrNi2Mo钢在形变过程中板条块取向逐渐呈现择优分布。

英文摘要：

The isothermal single-pass hot compression test of 20CrNi2Mo lath martensite steel was carried out on a DIL805A/T thermomechanical simulator.The effect of deformation on microstructure evolution and mechanical properties of the 20CrNi2Mo steel was investigated by means of optical microscope（ OM）,scanning electron microscopy（ SEM）,electron backscattered diffraction（ EBSD）technique and micro-hardness test.The results show that the dynamic recrystallization easily occurs in the process of hot compression and the critical strain（ εc） is 0.22.When the deformation is less than εc,the prior austenite grain size changes little,but the marensite packet size increases while block width decreases.Meanwhile,the proportion of the low angle grain boundary increases gradually,and the proportion of the large angle grain boundary decreases gradually.When the deformation exceeds the critical strain,with the increasing of deformation,the prior austenite grain size,marensite packet size and block are gradually refined,and the proportion of the low angle grain boundary first decreases slightly and then increases gradually.The pole figure analysis shows that the preferential distribution of the block orientation of the 20CrNi2Mo steel appears during the deformation.