【摘要】 以一种超超临界电站管材用镍基合金为研究对象,结合管材的冷热加工过程及系列压缩热变形与固溶退火实验,利用OM和TEM等手段分析了该合金热加工过程中的动、静态再结晶行为。结果表明:该合金的动态再结晶过程是以晶界弓弯方式形核的非连续动态再结晶为主,静态再结晶则以应变诱导晶界迁动形核机制为主。此外,动态再结晶与静态再结晶过程中产生的不同形态的台阶晶界,其本质是实现表面对低指数面的偏离,保证更多晶界面为低能密排面,以使晶界界面能降低;其形态取决于晶界面的晶体学关系以及晶界位错的Burgers矢量;台阶晶界的存在还可以促进晶界迁移,加速再结晶过程。而且,在再结晶过程进行完全后,台阶晶界仍部分保留,以降低界面能并继续促进后续的晶粒长大过程。更多还原

【Abstract】 Nickel-based alloy is a good choice for materials used in ultra-supercritical power plant,which is subjected to high temperature about 700 ℃ and high pressure in service. In order to meet the requirements above, a nickel-based alloy was designed and the tubes were successfully manufactured.Based on the hot/cold working processes of tube components of the nickel-based alloy, microstructural evolution, especially the recrystallization mechanisms during hot working processes of the alloy were systematically investigated by using a series of hot compression tests, solution annealing tests, OM and TEM analyses. The results showed that dynamic recrystallization was dominated by discontinuous dynamic recrystallization mechanism involving grain boundary bulging, whereas the nucleation mechanism with strain inducing grain boundary migration was the driving force of static recrystallization. In addition,the essence of different forms of step grain boundary producing during dynamic recrystallization and static recrystallization was to make the surface deviate from low index surface, which could ensure more interface to be low energy close-packed surface, so that the energy of grain boundary interface would be reduced. The morphology of step grain boundary depended on the crystallographic relationship of crystal interface and the Burgers vector of grain boundary dislocation. Moreover, the presence of step grain boundary could also promote grain boundary migration and accelerate the recrystallization process.When the recrystallization process was completed, step grain boundaries still remained partially to minimize interfacial energy and continue to promote subsequent grain growth processes.更多还原