The asymmetry of cyclic hardening in Ni/sub 3/(Al, Nb) single crystals

Journal Article · Sat Jun 01 04:00:00 EDT 1985 · Scr. Metall.; (United States)

DOI:https://doi.org/10.1016/0036-9748(85)90037-7· OSTI ID:6490876

Ezz, S S; Pope, D P

There are numerous similarities in the mechanical behavior between L1/sub 2/ alloys and bcc metals, such as the breakdown of Schmid's law, a strong orientation and temperature dependence of the flow stress and changes of the slip geometry. (The details of these effects are different in the L1/sub 2/ and bcc materials, but the effects exists in both materials.) All these features originate from characteristic properties of the core structure of screw dislocations. When bcc single crystals are cyclically deformed, an increasing stress asymmetry is observed which was shown in both Nb and Mo single crystals to be orientation dependent. The purpose of the study reported here is to determine if such asymmetries of the flow stress can be observed in a pure ..gamma..' alloy during cyclic deformation. The cyclic hardening of Ni/sub 3/(Al, Nb) crystals tested under plastic strain control is anistropic. The mean stress is always non zero for the orientations and temperatures selected for this study. The fatigue hardening behavior of this material corresponds, in general, to the flow behavior under monotonic test conditions. The sense of asymmetry in cyclic hardening follows the same orientation dependence as that of samples tested monotonically. The mean stress, which is a measure of asymmetry, is almost zero for plastic strains in the microyield region. The near-(011) orientation shows the largest asymmetry. The influence of cycling on the mean stress is very weak for the near-(001) sample, moderate for the near-(111) sample and very strong for the near-(011) sample.

• Research Organization: Department of Materials Science and Engineering, University of Pennsylvania Philadelphia, PA
• OSTI ID: 6490876
• Journal Information: Scr. Metall.; (United States), Journal Name: Scr. Metall.; (United States) Vol. 19:6; ISSN SCRMB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
ALLOYS
ALUMINIUM ALLOYS
ANISOTROPY
ASYMMETRY
BCC LATTICES
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTALLIZATION
CRYSTALS
CUBIC LATTICES
DESTRUCTIVE TESTING
FATIGUE
FLOW STRESS
GRAIN ORIENTATION
HARDENING
MATERIALS TESTING
MECHANICAL PROPERTIES
MICROSTRUCTURE
MONOCRYSTALS
NICKEL ALLOYS
NICKEL BASE ALLOYS
NIOBIUM ALLOYS
ORIENTATION
PHASE TRANSFORMATIONS
STRESS ANALYSIS
STRESSES
TESTING