采用Gleeble-3500热模拟试验机进行高温等温压缩实验,研究了变形条件对GH690合金高温变形动态再结晶的影响.结果表明:GH690合金动态再结晶过程是一个受变形温度和应变速率控制的过程,在应变速率为0.001～1 s-1的实验条件下,GH690合金获得完全动态再结晶组织所需的温度随变形速率的增大而升高；动态再结晶晶粒尺寸随变形温度升高而增大.采用力学方法直接从流变曲线确定了GH690合金发生动态再结晶的临界应变量,并回归出临界应变量与Z参数的关系式:εc=1.135×10-3Z0.14233.GH690合金的主要动态再结晶机制是原始晶界凸起形核的不连续动态再结晶机制(DDRX),而新晶粒通过亚晶逐渐转动而形成的连续动态再结晶机制(CDRX)则起辅助作用.
Hot compression tests were conducted using a Gleeble-3500 thermomechanical simulator to investigate the effect of hot deformation conditions on dynamic recrystallization (DRX) of GH690 alloy.The results show that the DRX process of GH690 alloy is controlled by deformation temperature and strain rate.Under the investigated condition at a constant strain rate ranging from 0.001 to 1 s-1,the temperature needed for fully dynamic recrystallization increases with the increases of strain rate,and the size of dynamically recrystallized grain is greatly affected by the increase of deformation temperature.The values of critical strain for the initiation of DRX can be determined from the strain-stress curves,and a equation related to the Zener-Hollomon Parameter is as follows:εc =1.135×10-3Z0.14233.A discontinuous dynamic recrystallization (DDRX) mechanism with nucleation of bulging of the original grain boundaries is the operating nucleation mechanism of DRX of GH690 alloy.A continuous dynamic recrystallization (CDRX) with subgrain rotation,which can only be considered as an assistant nucleation mechanism of DRX,occurs simultaneously with the DDRX.
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