Creep-fatigue behavior of annealed Cu-Cr-Zr alloy tested at 650 K and 750 K

摘要

A Cu-0.7Cr-0.09Zr (mass %) alloy is utilized in the rocket engine combustion chamber for the rocket JAXA is in the process of developing. As the inner cylinder material, the Cu-Cr-Zr alloy will be exposed to an extreme environment and thus it is important to understand how the material will behave in that environment to accurately estimate the lifetime of the rocket engine. In this investigation, fully-annealed Cu-Cr-Zr specimens are creep-fatigue tested at 650 K by cycling periods of strain-controlled compression and stress-controlled creep to understand the material's deformation and damage behavior in the usage environment. The results are then compared to those of similar tests done at 750 K to develop an understanding of the effect of temperature on the materials behavior in this extreme environment. SEM observation of the fracture surfaces and vertical cross-sectional surfaces suggests that fatigue is dominant over creep in the damage behavior of the fully annealed alloy at both 650 K and 750 K. TEM observation of the microstructures shows a similar progression in dislocation cell structure formation, but a more in-depth look shows that temperature affects the rate of formation of the dislocation cells which changes the deformation behavior of the material.