Transition of Serration Types during the Portevin–Le Chatelier Effect in GH4169 Superalloy under Varying Deformation Conditions
摘要
The serrated flow behavior, known as the Portevin–Le Chatelier (PLC) effect, significantly influences the mechanical performance of nickel-based superalloys under service conditions. This study systematically investigates the transition of serration types in GH4169 superalloy during uniaxial tensile deformation across a range of temperatures (200-700 °C) and strain rates (10−4–10−2 s−1). Serration types (A, B, and C) were identified and characterized through true stress–strain analysis and quantified using critical strain, serration amplitude, and drop time. The results reveal a strong dependence of serration type on both temperature and strain rate: type A dominates at low temperatures and high strain rates, type B appears at intermediate temperatures and low strain rates, and type C emerges near 600 °C at moderate strain rates. Activation energy calculations based on multiple methods indicate that different solute atoms govern serration formation at varying temperatures: carbon at low temperatures and substitutional atoms (Cr, Fe, Mo) at high temperatures. Microstructural observations by SEM/TEM corroborate the proposed serration mechanisms, linking them to solute-dislocation interactions and deformation twins. These findings provide mechanistic insights into the PLC effect in GH4169 alloy and offer valuable guidance for optimizing mechanical performance in high-temperature applications.