TY - JOUR
T1 - Effect of strain rate cycling on microstructures and crystallographic preferred orientation during high-temperature creep
AU - Peternell, Mark
AU - Wilson, Christopher J L
PY - 2016
Y1 - 2016
N2 - Strain rate histories and strain magnitude are two crucial factors governing the evolution of dynamic recrystallized grain size and crystallographic preferred orientation (CPO) in rocks and ice masses. To understand the effect of cyclic variations in strain rate or non-steadystate deformation, we conducted two-dimensional, coaxial plane strain experiments with time-lapse observations from a fabric analyzer. There is a continuous reequilibration of microstructure and CPO development associated with constant and oscillating strain rate cycles. These can be correlated with c-axis small circle distributions, diagnostic of dynamic recrystallization involving new grain nucleation and grain boundary migration (GBM) as observed in the high-temperature deformation of ice and quartz. Inhomogeneous stress distribution can lead to grain size reduction for relatively slower strain rates and GBM for relatively faster rates within a long-interval cycling event, a behavior that contradicts the classic view for dynamic recrystallization processes. Where there is a rapid short-term cycling of strain rate, GBM is hampered and nucleation dominates, accompanied by a marked reduction of grain size and no new CPO development. During such short-term cycling, GBM and crystallographic change is impeded not by impurities, but by an inability of newly nucleated grains to grow.
AB - Strain rate histories and strain magnitude are two crucial factors governing the evolution of dynamic recrystallized grain size and crystallographic preferred orientation (CPO) in rocks and ice masses. To understand the effect of cyclic variations in strain rate or non-steadystate deformation, we conducted two-dimensional, coaxial plane strain experiments with time-lapse observations from a fabric analyzer. There is a continuous reequilibration of microstructure and CPO development associated with constant and oscillating strain rate cycles. These can be correlated with c-axis small circle distributions, diagnostic of dynamic recrystallization involving new grain nucleation and grain boundary migration (GBM) as observed in the high-temperature deformation of ice and quartz. Inhomogeneous stress distribution can lead to grain size reduction for relatively slower strain rates and GBM for relatively faster rates within a long-interval cycling event, a behavior that contradicts the classic view for dynamic recrystallization processes. Where there is a rapid short-term cycling of strain rate, GBM is hampered and nucleation dominates, accompanied by a marked reduction of grain size and no new CPO development. During such short-term cycling, GBM and crystallographic change is impeded not by impurities, but by an inability of newly nucleated grains to grow.
UR - http://geology.gsapubs.org/content/early/2016/02/24/G37521.1.full.pdf+html
U2 - 10.1130/G37521.1
DO - 10.1130/G37521.1
M3 - Article
VL - 44
SP - 279
EP - 282
JO - Geology
JF - Geology
SN - 0091-7613
IS - 4
ER -