Tension/compression asymmetry in yield and creep strengths of Ni-based superalloy with a high amount of tantalum

The asymmetry of tensile/compressive yield strengths of single crystal Ni-based superalloys has been explained by the thermally activated cross-slip model. In contrast, the asymmetry of the creep strengths has been explained by the anisotropy of mechanical twin formation. In this study, a superalloy containing a high amount of tantalum was subjected to strength tests. Neither tension/compression asymmetry nor mechanical twinning was observed in the creep test. However, the tensile yield strength was higher than the compressive one, and micro-mechanical twinning was observed in the compressive yielded microstructure using high resolution transmission electron microscopy. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.