Temperature dependence of inelastic strain recovery in TiNi-based alloys under torsion

The mechanical behaviour of antigorite strongly influences the strength and deformation of the subduction interface. Although there is microstructural evidence elucidating the nature of brittle deformation at low pressures, there is often conflicting evidence regarding the potential for plastic deformation in the ductile regime at higher pressures. Here, we present a series of spherical nanoindentation experiments on aggregates of natural antigorite. These experiments effectively investigate the single-crystal mechanical behaviour because the volume of deformed material is significantly smaller than the grain size. Individual indents reveal elastic loading followed by yield and strain hardening. The magnitude of the yield stress is a function of crystal orientation, with lower values associated with indents parallel to the basal plane. Unloading paths reveal more strain recovery than expected for purely elastic unloading. The magnitude of inelastic strain recovery is highest for indents parallel to the basal plane. We also imposed indents with cyclical loading paths, and observed strain energy dissipation during unloading–loading cycles conducted up to a fixed maximum indentation load and depth. The magnitude of this dissipated strain energy was highest for indents parallel to the basal plane. Subsequent scanning electron microscopy revealed surface impressions accommodated by shear cracks and a general lack of dislocation-induced lattice misorientation. Based on these observations, we suggest that antigorite deformation at high pressures is dominated by sliding on shear cracks. We develop a microphysical model that is able to quantitatively explain Young’s modulus and dissipated strain energy data during cyclic loading experiments, based on either frictional or cohesive sliding of an array of cracks contained in the basal plane. This article is part of a discussion meeting issue ‘Serpentinite in the earth system’

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Temperature-Dependence of Multiaxial Non-Proportional Cyclic Behavior of Type 316 Stainless Steel

Journal of Engineering Materials and Technology ◽

10.1115/1.3226430 ◽

1989 ◽

Vol 111 (1) ◽

pp. 32-39 ◽

Cited By ~ 34

Author(s):

S. Murakami ◽

M. Kawai ◽

K. Aoki ◽

Y. Ohmi

Keyword(s):

Stainless Steel ◽

Temperature Dependence ◽

Uniaxial Tension ◽

Constant Strain Rate ◽

Inelastic Strain ◽

Cyclic Hardening ◽

Material Behavior ◽

Cyclic Behavior ◽

316 Stainless Steel ◽

Strain Paths

Temperature dependence of multiaxial cyclic behavior of type 316 stainless steel was elucidated experimentally. Cyclic tests under constant total-strain amplitudes were performed for uniaxial tension-compression and circular (non-proportional) strain paths at several temperatures; room temperature, 200°C, 400°C, 500°C, 600°C, and 700°C. The strain amplitudes of the cycles were specified to be 0.2, 0.3, and 0.4 percent under constant strain rate of 0.2 percent per min. A quantitative discussion was made with special emphasis on the difference between material behavior under uniaxial tension-compression strain cycles and multiaxial non-proportional circular ones at these temperatures. The most significant cyclic hardening was observed in the temperature range between 400°C and 600°C for both the proportional and the non-proportional strain cycles. At these particular temperatures, much larger inelastic strain was accumulated until a cyclic stabilization was obtained. Though the effect of non-proportionality in the cyclic strain paths on the cyclic hardening was significant particularly at the temperature below 450°C, it rapdily decreased at higher temperatures.

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