Research on Microstructure Transformation and Tensile- Rupture Properties of GH4706 Alloy under Long-Term Aging

To reveal the influence of long-term aging on the tensile- rupture properties and microstructure of GH4706 alloy, the microstructure, fracture morphology and mechanical properties after tensile at room temperature and rupture tests were analyzed for aging temperatures of 600, 650 and 675 ℃ and aging times of 3000 h and 5000 h. The results show that: (1) The grain size increases significantly with the increase of aging temperature/time, and mixed crystal phenomenon is prone to occur at high temperature and long aging time; (2) The precipitation of carbides and η phase follows the rule of "discrete at low temperature - dense at medium temperature - coarsening at high temperature", and the η phase changes from discrete particles to continuous needles; (3) The fracture mode changes from ductile fracture to brittle fracture, but the precipitation of dispersed carbides under enduring load can delay the transformation process; (4) Based on the comprehensive results of tensile and rupture tests, the process window is determined, with the aging temperature controlled not higher than 650 ℃ and the aging time of 3000 h, to achieve the control of microstructure- properties.