中文摘要：

采用Gleeble-1500热模拟试验机,对GH625合金进行了以不同变形温度、不同应变速率变形到真应变值为0.7的热压缩试验,以研究其热变形过程的动态再结晶组织演变.利用光学显微镜（OP）和透射电镜（TEM）分析了应变速率对GH625合金热变形过程中的组织演变及动态再结晶形核机制的影响.结果表明：应变速率·ε=10.0s~（-1）时,实际变形温度高于预设温度,产生变形热效应.GH625合金热变形过程的组织演变是一个受应变速率和变形温度控制的过程,在应变速率·ε≤1.0s~（-1）时,GH625合金动态再结晶晶粒的尺寸及体积分数随着应变速率的升高而降低,动态再结晶形核机制是由晶界弓弯的不连续动态再结晶机制和亚晶旋转的连续动态再结晶机制组成;在应变速率·ε=10.0s~（-1）时,由于变形热效应使动态再结晶晶粒的尺寸及体积分数迅速升高,动态再结晶机制则是以弓弯机形核的不连续动态再结晶机制为主.

英文摘要：

Hot compression tests were conducted on a Gleeble-1500 simulator at a true strain of 0.7 at different temperatures and different strain rates to investigate the dynamic recrystallization behavior of GH625 superalloy. Optical microscopy （OP） and transmission electron microscopy （TEM） were employed to analyze the effect of strain rate on the microstructural evolution and nucleation mechanisms of dynamic recrystallization （DRX）. The results show that the actual deformation temperature of the sample deformed at a strain rate of 10.0s~（-1） is higher than the preset temperature, resulting in a deformation thermal effect. It is also found that the DRX of GH625 superalloy is controlled by both strain rate and deformation temperature. When the strain rate ε·≤1.0s~（-1）, the size and volume fraction of DRX grains decrease with increasing strain rate. The nucleation mechanism of DRX is composed of discontinuous dynamic recrystallization （DDRX） characterized by the bulging of original grain boundaries and continuous dynamic recrystallization （CDRX） characterized by progressive subgrain rotation. However the size and volume fraction of DRX grains increase at a strain rate of 10.0s~（-1） due to the deformation thermal effect. The nucleation mechanism of DRX for GH625 superalloy deformed at a strain rate of 10.0s~（-1） is operating by DDRX with the bulging of original grain boundaries.