Effect of growth rate on elevated temperature plastic flow and room temperature fracture toughness of directionally solidified NiAl-31Cr-3Mo

The eutectic system Ni-33Al-31Cr-3Mo was directionally solidified at rates ranging from 7.6 to 508 mm/h. Samples were examined for microstructure and alloy chemistry, compression tested at 1200 and 1300 K, and subjected to ro om temperature fracture toughness measurements. Lamellar eutectic grains we re formed at 12.7 mm/h; however, cellular structures with a radial eutectic pattern developed at faster growth rates. Elevated temperature compression testing between 10(-4) to 10(-7) s(-1) did not reveal an optimum growth co ndition, nor did any single growth condition result in a significant fractu re toughness advantage. The mechanical behavior, taken together, suggests t hat Ni-33Al-31Cr-3Mo grown at rates from 25.4 to 254 mm/h will have nominal ly equivalent properties (C) 1999 Elsevier Science Ltd. All rights reserved .