Strain Rate Sensitivity Of Alloys 800h And 617

The flow stress of many materials is a function of the applied strain rate at elevated temperature. The magnitude of this effect is captured by the strain rate sensitivity parameter "m". The strain rate sensitivity of two face center cubic solid solution alloys that are proposed for use in high temperature heat exchanger or steam generator applications, Alloys 800H and 617, has been determined as a function of temperature over that range of temperatures relevant for these applications. In addition to determining the strain rate sensitivity, it is important for nuclear design within Section III of the ASME Boiler and Pressure Vessel Code to determine temperature below which the flow stress is not affected by the strain rate. This temperature has been determined for both Alloy 800H and Alloy 617. At high temperature the strain rate sensitivity of the two alloys is significant and they have similar m values. For Alloy 617 the temperature limit below which little or no strain rate sensitivity is observed is approximately 700 degrees C. For Alloy 800H this temperature is approximately 650 degrees C.