Hardening by bubbles in He-implanted Ni

Journal Article · Tue Jan 01 00:00:00 EST 2008 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.2831205· OSTI ID:21064495

Knapp, J A; Follstaedt, D M; Myers, S M ^[1]

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1. Sandia National Laboratories, Albuquerque, New Mexico 87185-1056 (United States)

Detailed finite-element modeling of nanoindentation data is used to obtain the mechanical properties of Ni implanted with 1-10 at. % He. The mechanical properties of this material elucidate the fundamental materials science of dislocation pinning by nanometer-size gas bubbles and also have implications for radiation damage of materials. Cross-section transmission electron microscopy showed that implantation of 1-5 at. % He at room temperature or at 200 deg. C produced a highly damaged layer extending to a depth of 700-800 nm and containing a fine dispersion of He bubbles with diameters of 1.1{+-}0.2 nm. Implantation at 500 deg. C enlarged the bubble sizes. By fitting the nanoindentation data with a finite-element model that includes the responses of both the implanted layer and the unimplanted substrate in the deformation, the Ni(He) layers are shown to have hardnesses as much as approximately seven times that of untreated Ni, up to 8.3{+-}0.6 GPa. Examination of the dependence of yield strength on He concentration, bubble size, and bubble density reveals that an Orowan hardening mechanism is likely to be in operation, indicating that the bubbles pin dislocation motion as strongly as hard second-phase precipitates do. This strong pinning of dislocations by bubbles is also supported by our numerical simulations, which show that substantial applied shear stress is required to move a dislocation through an empty cavity.

• OSTI ID: 21064495
• Journal Information: Journal of Applied Physics, Vol. 103, Issue 1; Other Information: DOI: 10.1063/1.2831205; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BUBBLES
CROSS SECTIONS
DEFORMATION
DISLOCATION PINNING
DISLOCATIONS
FINITE ELEMENT METHOD
HARDENING
HARDNESS
ION IMPLANTATION
LAYERS
NICKEL
PRECIPITATION
PRESSURE RANGE GIGA PA
RADIATION EFFECTS
SIMULATION
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0273-0400 K
TEMPERATURE RANGE 0400-1000 K
TRANSMISSION ELECTRON MICROSCOPY
YIELD STRENGTH