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Title:: The Effect of Aging Treatment Temperature on Microstructure and Stress-Rupture Properties of a Fourth Generation Ni-Based Single Crystal Superalloy

Author(s):: LI Yuan; ZHAO Yunsong; GUO Yuanyuan; ZHANG Jian; YANG Zhenyu; ZHENG Shuai; LIU Chenguang; TANG Dingzhong; Science and Technology on Advanced High Temperature Structural Materials laboratory, Beijing Institute of Aeronautical Materials, Beijing 100095, China

Keywords:: Ni-based single crystal superalloy; aging treatment; microstructure; high temperature stress-rupture property; fracture morphology

Abstract:: To investigate the influence of primary aging temperature on the microstructure and stress-rupture properties of a fourth-generation Ni-based single-crystal superalloy, high-resolution field emission scanning electron microscopy and optical microscopy were employed to characterize microstructural evolution during heat treatment, high-temperature stressrupture fracture morphology and microstructure of cross-sections. The results revealed that solution treatment effectively eliminated (γ+γ′) eutectic structures and substantially reduced elemental segregation. Primary aging modified γ′ precipitate size and morphology, where increasing temperature promoted γ′ coarsening in dendritic areas, diminished cuboidal integrity and widened γ matrix channels. Consequently, elevated primary aging temperatures reduced the stress-rupture life at 1120 ℃/137 MPa. The stressrupture performance exhibited critical dependence on γ′ precipitate morphology, size, volume fraction and γ channel width. Optimally sized, highly cuboidal γ′ precipitates strongly impeded dislocation motion, while the Orowan stress for dislocation glide within γ channels demonstrated inverse proportionality to channel width. Comprehensive evaluation established 1140 ℃ as the optimal primary aging temperature for this alloy.