一种先进超超临界火电机组用Ni-Fe-Cr基高温合金的热变形行为

Hot Deformation Behavior of a Ni-Fe-Cr Based Superalloy for Advanced Ultra-supercritical Coal-fired Power Plants Application

通过不同变形参数下的等温压缩实验,研究了一种Ni-Fe-Cr基高温合金的热变形行为及动态再结晶机理。结果表明,合金的流变应力随着变形温度的降低或应变速率的升高而增大,而动态再结晶比例随着变形温度的降低或应变速率的升高而降低,但受温升效应影响,应变速率高于1 s-1时,动态再结晶比例随着应变速率的升高而升高。合金合理的热变形温度为1100~1200℃,应变速率为0.01~0.3 s-1。热变形参数对合金的动态再结晶机理产生影响,高温低应变速率变形时,合金的主要再结晶机理为以晶界弓弯为主要特点的非连续动态再结晶,而低温高应变速率变形时,以晶内亚晶发展为主要特点的连续动态再结晶也发挥重要的作用。

The deformation behavior of a Ni-Fe-Cr based superalloy for 700℃advanced ultra-supercritical(A-USC)power plant application was studied by the isothermal compression test at temperature range of 900—1200℃with strain rates of 0.01—10 s-1 on a Gleeble-1500 thermo-mechanical simulator.The results showed that the flow stress increased with the decreasing temperature and the increasing strain rate.The fraction of dynamic recrystallization decreased with the decreasing temperature and the increasing strain rate.However,when the strain rate was higher than 1 s-1,the fraction of dynamic recrystallization rose with the increasing strain rate due to the effect of adiabatic heating.The reasonable deformation temperature range of the alloy was 1100—1200℃,and the strain rate range was 0.01—0.3 s-1.The nucleation mechanism of dynamic recrystallization in the alloy was discontinuous dynamic recrystallization due to the existence of original grain boundaries bulging at high temperature and low strain rate.However,the dominant nucleation mechanism of dynamic recrystallization at low temperature and high strain rate turned into continuous dynamic recrystallization featured by sub-grains development within the original grains.