Low cycle fatigue behavior of polycrystalline Ni[sub 3]Al alloys at ambient and elevated temperatures
- AlliedSignal Engines, Phoenix, AZ (United States)
- Washington State Univ., Pullman, WA (United States). Dept. of Mechanical and Materials Engineering
The low cycle fatigue (LCF) resistance of polycrystalline Ni[sub 3]Al has been evaluated at ambient, intermediate (300 C), and elevated (600 C) temperatures using strain rates of 10[sup [minus]2]/s and 10[sup [minus]4]/s. Testing was conducted on a binary and a Cr-containing alloy of similar stoichiometry and B content. Test results were combined with electron microscope investigations in order to evaluate microstructural changes during LCF. At ambient and intermediate temperatures, the cyclic constitutive response of both alloys was similar, and the LCF behavior was virtually rate independent. Under these conditions, the alloys rapidly hardened and then gradually softened for the remainder of the life. Initial hardening resulted from the accumulation of dislocation debris within the deformed microstructure, whereas softening was related to localized disordering. For these experimental conditions, crack initiation resulted within persistent slip bands (PSBs). At the elevated temperature, diffusion-assisted deformation resulted in a rate-dependent constitutive response and crack-initiation characteristics. At the high strain rate, continuous cyclic hardening resulted from the accumulation of dislocation debris. At the low strain rate, the diffusion of dislocation debris to grain boundaries resulted in cyclic softening. The elevated temperature LCF resistance was determined by the effect of the constitutive response on the driving force for environmental embrittlement. Chromium additions were observed to enhance LCF performance only under conditions where crack initiation was environmentally driven.
- OSTI ID:
- 6999335
- Journal Information:
- Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States), Vol. 25:11; ISSN 0360-2133
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ALUMINIUM ALLOYS
FATIGUE
MICROSTRUCTURE
CHROMIUM
METALLURGICAL EFFECTS
NICKEL BASE ALLOYS
CRACK PROPAGATION
EXPERIMENTAL DATA
INTERMETALLIC COMPOUNDS
ALLOYS
DATA
ELEMENTS
INFORMATION
MECHANICAL PROPERTIES
METALS
NICKEL ALLOYS
NUMERICAL DATA
TRANSITION ELEMENTS
360103* - Metals & Alloys- Mechanical Properties
360102 - Metals & Alloys- Structure & Phase Studies