CRSS ANISOTROPY AND TENSION COMPRESSION ASYMMETRY OF A COMMERCIAL SUPERALLOY/

The critical resolved shear stresses (CRSS) of the gamma'-strengthened nickel-based superalloy NIMONIC 105 and of its two constituent phases -disordered f.c.c. gamma-matrix and L1(2)-long-range ordered gamma'-ph ase-have been measured in tension and compression. The single crystals had the following orientations: [001], [011], [(1) over bar 11], and [(1) over bar 23]; the deformation temperatures T ranged from 283 to 1 150 K. The dislocation processes in NIMONIC 105 have been studied by t ransmission electron microscopy and slip trace analyses. The CRSS tau( o) of single-phase gamma'-crystals showed the abnormalities which have been observed for many other L1(2)-long-range ordered materials: (i) positive slope a partial derivative tau(o)/partial derivative T, (ii) anisolropy; (iii) tension/compression (t/c) asymmetry, tau(o) of two-p hase NIMONIC 105 has anisotropies and (t/c) asymmetries which are simi lar to those of single-phase gamma', but they are less pronounced, tau (o) of NIMONIC 105 is, however, nearly independent of T for 400 K less than or equal to T less than or equal to 1000 K. Copley and Kear's dy namic model (Trans. Am. Inst. Min. Engrs, 1967, 239, 984) has been ada pted to relate tau(o) of two-phase NIMONIC 105 to tau(o) of its consti tuent single-phase gamma'- and gamma'-phase. (C) 1998 Acta Metallurgic a Inc. Published by Elsevier Science Ltd. All rights reserved.