The effect of thermo-mechanical treatment on the high temperature tensile behavior of an alumina-forming austenitic steel

Two different thermo-mechanical treatments (TMT) were performed on an alumina-forming austenitic (AFA) stainless steel, DAFA 29, which was recently developed at Oak Ridge National Laboratory for application in advanced ultra supercritical power plants. The resulting fine-grained TMT materials showed yield stresses more than double the yield stress of the as-received material at room temperature and more than 50% higher at 600 degrees C, but lower yield stresses (but greater elongations) at 700 degrees C and above. Strain rate jump tests performed at both 600 degrees C and 700 degrees C showed that the TMT materials have greater strain rate sensitivity and lower activation volumes at both temperatures. The strain rate has a power law relationship with the flow stress with a stress exponent of similar to 5. The as-received AFA alloy showed serrated stress-strain curves at 600 relationship with the flow stress with a stress exponent of 5. The as-received AFA alloy showed serrated C suggesting the occurrence of dynamic strain aging. (c) 2015 Elsevier B.V. All rights reserved.