中文摘要：

利用Gleeble 1500热模拟试验机进行单轴热压缩实验，结合SEM，TEM和EBSD等方法研究了过共析钢温变形过程中的组织演变规律，重点讨论了铁素体的等轴化演变过程，同时考察了合金元素Al的影响．结果表明：过共析钢温变形经历片层渗碳体的熔断球化、铁素体的等轴化以及渗碳体的溶解再析出等过程．温变形初期，片层状渗碳体缺陷处局部熔断的同时其近邻铁素体内产生大量位错，并通过动态回复过程形成亚晶；继续变形过程中，由于渗碳体粒子钉扎，亚晶发生转动，导致大角度晶界的形成，即铁素体通过连续动态再结晶过程实现等轴化．Al的加入细化了铁素体晶粒尺寸，提高了等轴状铁素体晶粒大角度晶界的比例．

英文摘要：

The microstructure evolution of hypereutectoid steels during warm deformation was investigated by uniaxial hot compression simulation experiment and by means of SEM, TEM and EBSD, especially for the formation of equiaxial ferrite grains and the effects of Al on the formation of equiaxial ferrite grains. The results indicate that the microstructure evolution of hypereutectoid steel during warm deformation involves the spheroidization of lamellar cementite, the equiaxial process of ferrite and the re-precipitation of cementite particles. At the beginning of warm deformation, lots of dislocations are introduced into ferrite, and subgrain boundaries are formed by dynamic recovery of ferrite. With the strain increasing, subgrains rotate due to the pinning effect of cementite particles, leading to the formation of high angle grain boundaries, i.e., the formation of equiaxial ferrite grains is actualized by the dynamic continuous recrystallization of ferrite. By the addition of Al, the coarsening of cementite is hindered, the sizes of cementite particles and ferrite grains are refined and the fraction of high angle grain boundary is increased.