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Load relaxation of olivine single crystals
Author(s) -
Cooper Reid F.,
Stone Donald S.,
Plookphol Thawatchai
Publication year - 2016
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1002/2016jb013425
Subject(s) - creep , materials science , stress relaxation , olivine , exponent , relaxation (psychology) , strain rate , work hardening , hardening (computing) , dislocation , scaling , slip (aerodynamics) , stress (linguistics) , composite material , condensed matter physics , microstructure , thermodynamics , mineralogy , geology , geometry , physics , mathematics , psychology , social psychology , linguistics , philosophy , layer (electronics)
Single crystals of ferromagnesian olivine (San Carlos, AZ, peridot; ~Fo 88‐90 ) have been deformed in both uniaxial creep and load relaxation under conditions of ambient pressure, T = 1500°C and p O 2 = 10 −10 atm; creep stresses were in the range 40 ≤ σ 1 (MPa) ≤ 220. The crystals were oriented such that the applied stress was parallel to [011] c , which promotes single slip on the slowest slip system in olivine, (010)[001]. The creep rates at steady state match well the results of earlier investigators, as does the stress sensitivity (a power law exponent of n = 3.6). Dislocation microstructures, including spatial distribution of low‐angle (subgrain) boundaries, additionally confirm previous investigations. Inverted primary creep (an accelerating strain rate with an increase in stress) was observed. Load relaxation, however, produced a singular response—a single hardness curve—regardless of the magnitude of creep stress or total accumulated strain preceding relaxation. The log stress versus log strain rate data from load‐relaxation and creep experiments overlap to within experimental error. The load‐relaxation behavior is distinctly different than that described for other crystalline solids, where the flow stress is affected strongly by work hardening such that a family of distinct hardness curves is generated, which are related by a scaling function. The response of olivine for the conditions studied, we argue, indicates flow that is rate limited by dislocation glide, reflecting specifically a high intrinsic lattice resistance (Peierls stress).