Abnormal Stress Relaxation Behavior of GH4169 Alloy

Stress relaxation, creep and thermal expansion tests at 500, 620, 720℃ were conducted on GH4169 alloy, and then the stress relaxation behavior was studied by combination of microstructure observation. The results show that the stresses in the GH4169 alloy increased abnormalloy with increasing time during stress relaxation tests at 500℃ and 620℃, and showed negative creep strains during creep. However, the stress relaxation behavior and creep behavior of the alloy were normal at 720℃. Shrinkage was observed in the GH4169 alloy during thermal expansion tests at different temperatures. The reduction of lattice parameter of γ matrix, which was caused by the precipitation of γ″ phase, was the main reason for the abnormal increase of stresses in the GH4169 alloy at 620℃.