Effect of microstructure on work hardening behaviour of IN-617 alloy

Abstract

Work hardening behaviour of the IN-617 alloy under tensile loading was studied in the solution treated, aged, and cold worked conditions at room temperature (RT) and 700 °C. Double logarithmic plots of the true stress and logarithmic plastic strain of this alloy displayed upward concave shape similar to those of other austenitic superalloys. Five different relationships between the true stress and logarithmic plastic strain were analyzed to characterize the flow behaviour of this alloy. The relationship proposed by Ludwigson was found to have best fit with the experimental data. Three stages of the instantaneous work hardening rate (θ) were observed in the solution treated and the aged conditions whereas only stage I was exhibited in the cold worked condition of the alloy. Transmission electron microscopy (TEM) revealed traces of slip bands in the samples tested at RT and micro twins as well their interaction with dislocations and precipitation of new carbides was observed in the samples tested at 700 °C. There was typical ductile fracture with dimples in both the solution treated and aged conditions whereas there was faceted fracture in the cold worked condition both at RT and 700 °C.