Toughness of simulated heat-affected zone microstructures in HT-9 (ESR melt practice)

The toughness behavior of the heat-affected zone in the ESR National Fusion Heat was determined using Gleeble-simulated microstructures. Two regions of the HAZ were evaluated; one region represents the portion of the HAZ nearest the fusion zone, the other corresponds to a region which is heated only slightly above the upper critical temperature. Charpy V-notch results indicated that following a PWHT at 7600C for 1 hour both regions of the HAZ exhibit superior toughness behavior to that of the quench-and-tempered base material. The upper shelf toughness increased 20 to 40 Joules and the DBTT decreased nearly 200C relative to the base metal. The toughness of both the ESR base material and HAZ microstructures was superior to that of the AOD-processed National Fusion Heat, which had been previously tested in a similar manner