Influence of secondary precipitates and crystallographic orientation on the strength of single crystals of a Ni-based superalloy
- Tokyo Metropolitan Univ. (Japan). Dept. of Mechanical Engineering
The effect of crystallographic orientation and aging heat treatment at 850 C on the creep rupture strength of single crystals of a nickel-based superalloy was examined at 700 C in detail. Initial tensile orientations were selected over a wide range on the standard stereographic triangle. The {l_brace}111{r_brace}{l_angle}112{r_angle}-type slip systems were found to be operative during the creep deformation. The creep behavior was found to be greatly influenced by the additional aging at 850 C for 20 hours. It was found that the effect of the aging at 850 C was quite different between orientations favored for the ({bar 1}11)[1{bar 1}2] slip system and those favored for the (111)[{bar 2}11] slip system and that the creep deformation mechanisms of these two slip systems were different. In the orientations favored for ({bar 1}11)[1{bar 1}2] slip systems, in the single-aged specimens, a small mean surface-to-surface spacing due to hyperfine {gamma}{prime} precipitates in the matrix channel promoted the ({bar 1}11)[1{bar 1}2] slip and the primary creep. As a result of the additional aging at 850 C, the hyperfine {gamma}{prime} precipitates were dissolved into the matrix, and the resultant large mean surface-to-surface spacing between the cuboidal precipitates inhibited extensive shearing of the {gamma}-{gamma}{prime} structure by the ({bar 1}11)[1{bar 1}2] slip system. In the orientations favored for the (111)[{bar 2}11] slip system, creep deformation occurred by twinning shear through {gamma} and {gamma}{prime} precipitates, and a distinct effect of the aging at 850 C was not observed. In the multiple orientation of the {l_brace}111{r_brace}{l_angle}{bar 2}11{r_angle}-type slip systems, i.e., the [{bar 1}12] and [{bar 1}11] orientations, hyperfine precipitates improved creep strength because they prevented dislocations from gliding in the matrix channel in the single-aged specimens.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 363984
- Journal Information:
- Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science, Vol. 30, Issue 5; Other Information: PBD: May 1999
- Country of Publication:
- United States
- Language:
- English
Similar Records
Temperature dependence of additional cyclic hardening of a nickel-base superalloy during out-of-phase multiaxial deformation
On the formation of {l_angle}010{r_angle}-dislocations in the {gamma}{prime}-phase of superalloy single crystals during high temperature low stress creep