Creep Deformation and Microstructure of Alloy 617 Foil at High Temperature

The present paper reports the results of microcreep tests and microstructure of alloy 617 foils of 100 mu m thick specimens at 800 and 900 degrees C in air. Before each test, the specimens were annealed in vacuum at 950 degrees C for 17 hrs. The dynamic recrystallizations were observed during creep test. The voids and cracks were observed along grain boundaries. The maximum elongation of grains was found at the lowest applied stress along the loading direction. The average grain size decreases from 20 mu m to 2 mu m as applied stress increases from 48 to 120 MPa at 800 degrees C and from 50 mu m to 5 mu m as the applied stress increases from 35 to 60MPa at 900 degrees C. The steady state creep rates were increased as applied stress increased in all the specimens.