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采用Gleeble-3800热模拟试验机研究了GH625合金在变形温度为950～1150℃,应变速率为0.001～5s-1条件下的热变形特性,并用OM和TEM分析了变形条件对微观结构的影响。结果表明:当应变量很小时,该合金没有发生再结晶,直到应变量达到0.1时才开始有再结晶晶粒析出。随着变形温度的升高,再结晶晶粒尺寸增大,位错密度降低;当温度较低时显微结构中可以观察到孪晶。当变形温度一定时,随应变速率的增大,再结晶的形核率增大且晶粒变小,位错密度变大;而当应变速率较低时,再结晶进行得比较充分,晶粒尺寸较大。根据实测的应力-应变曲线,获得了该合金发生动态再结晶的临界应变εc和峰值应变εp与Z参数之间的关系:εc=2.0×10-3.Z0.12385,lnεp=-6.02285+0.12385lnZ。此外,还采用定量金相法计算出了合金的动态再结晶体积分数,并建立了该合金动态再结晶的动力学模型:Xd=1-exp[-0.5634(ε/εp-0.79)1.313]。
The thermal deformation characteristics of GH625 alloy at 950 ~ 1150 ℃ and 0.001 ~ 5s-1 strain rate were studied by Gleeble-3800 thermal simulator. The effects of deformation conditions on microstructure were analyzed by OM and TEM. The results show that when the amount of strain is small, the alloy does not recrystallize until the amount of strain reaches 0.1, recrystallized grains begin to precipitate. With the increase of deformation temperature, the recrystallization grain size increases and the dislocation density decreases. When the temperature is low, the twins can be observed in the microstructure. When the deformation temperature is constant, as the strain rate increases, the nucleation rate of recrystallization increases and the grains become smaller, and the dislocation density becomes larger. When the strain rate is lower, the recrystallization proceeds sufficiently. Larger size. According to the measured stress-strain curve, the relationship between the critical strain εc and peak strain εp and the Z parameter of the dynamic recrystallization of the alloy is obtained: εc = 2.0 × 10-3.Z0.12385, lnεp = -6.02285 + 0.12385 lnZ. In addition, the dynamic recrystallization volume fraction of the alloy was also calculated by the quantitative metallographic method. The kinetic model of dynamic recrystallization was established as follows: Xd = 1-exp [-0.5634 (ε / εp-0.79) 1.313].