ELASTIC-CONSTANTS OF SINGLE-CRYSTAL HASTELLOY-X AT ELEVATED-TEMPERATURES

An acoustic time of flight technique is described in detail for measur ing the elastic constants of cubic single crystals that allows for the constants to be determined at elevated temperature. Although the over all technique is not new, various aspects of the present work may prov e extremely useful to others interested in finding these values, espec ially for aerospace materials applications. Elastic constants were det ermined for the nickel based alloy, Hastelloy X from room temperature to 1000 degrees C. Accurate elastic constants were needed as part of a n effort to predict both polycrystal mechanical properties and the nat ure of grain induced heterogeneous mechanical response. The increased accuracy of the acoustically determined constants resulted in up to a 15 percent change in the predicted stresses in individual grains. Thes e results indicate that the use of elastic single crystal constants of pure nickel as an approximation for the constants of gas turbine sing le crystal alloys, which is often done today, is inaccurate.