Abstract: A cast article is heat treated by vacuum annealing at an annealing temperature above the alpha/beta transition temperature of the cast article. Further, the cast article is subjected to a hot isostatic pressing step and a post-weld stress relief processing step. The vacuum annealing step is executed prior to the hot isostatic pressing step and the hot isostatic pressing step is executed prior to the post-weld stress relief processing step. The resulting impact resistance of the heat treated cast article, as measured by the Charpy test, represents an increase of approximately 50-200%, as compared to the untreated cast article. Further, even where the article is subjected to a post-HIP anneal the impact resistance increases by approximately 10-50%.