Iron GH2036 alloy residual stress thermal relaxation behavior in laser shock processing

• LSP has a remarkable influence on residual stress of Iron GH2036.
• Thermal relaxation of LSP GH2036 mainly occurred in the initial annealing time.
• Thermal relaxation is dominated by annealing temperature and time.
• A novel mechanism is proposed to explain stress relaxation of LSP GH2036.

Laser shock processing (LSP) has a significant effect on the fatigue performance of Iron GH2036 alloy by inducing a deep compressive residual stress field. The effects of isothermal annealing treatments on Iron GH2036 alloy compressive residual stress after laser shock processing at various temperatures ranging from 200 °C to 650 °C were studied comprehensively using experimental and simulation methods. The thermal stability of compressive residual stress induced by LSP was investigated. The residual stress distributions of original and processed specimens were measured by the X-ray diffraction method. The results showed that the experimental measurements were well consistent with the simulation data. Residual stress of laser shock processing Iron GH2036 alloy had released but not completely released at the selected temperatures and during the initial exposure period (less than 30 min); the thermal relaxation magnitude was large and increased with the rise of applied temperature. We infer that the main mechanism of thermal relaxation is the mechanism involving rearrangement and annihilation of dislocation.