At high pressure prevailing in the lower mantle, lattice friction opposed to dislocation glide becomes very high, as reported in recent experimental and theoretical studies. We examine the consequences of this high resistance to plastic shear exhibited by ringwoodite and bridgmanite on creep mechanisms under mantle conditions. To evaluate the consequences of this effect, we model dislocation cr...

Diffusion-controlled-creep processes are used to assess the creep behavior of dispersion and solute hardened materials at coarse and fine grain sizes. It is shown that the creep behavior of a dispersion strengthened (DS) Al–Mg alloy is similar to the creep behavior of pure Al–Mg alloys. Both materials show dislocation climb and dislocation solute-drag contributions to creep. It is shown that th...

A simple model based on the Orowan equation and the dynamic evolution of the dislocation structure by generation and merging of slipped areas is used to see which experimental results on creep of pure and solute-hardened crystalline materials can or cannot be explained with regard to creep with refinement or coarsening of the dislocation structure and steady-state creep. Quantitative deficienci...

steady state creep of the alloy was in a thermodynamical steady state, (2) which configuration of the dislocation network was contributing to the creep strength, and (3) which change in the dislocation network was the cause of the creep recovery. Specimens were furnace-cooled under stress and then observed by transmission electron microscopy. The creep stress was reduced during the test and the...

Here we report kinetic Monte Carlo simulations of dislocation climb in heavily deformed, body-centered cubic iron comprising a supersaturation of vacancies. This approach explicitly incorporates the effect of nonlinear vacancy-dislocation interaction on vacancy migration barriers as determined from atomistic calculations, and enables observations of diffusivity and climb over time scales and te...

In order to characterize the creep behaviors of 2219 aluminum alloy at different temperatures and stress levels, a RWS-50 Electronic Creep Testing Machine (Zhuhai SUST Electrical Equipment Company, Zhuhai, China) was used for creep experiment at temperatures of 353~458 k and experimental stresses of 130~170 MPa. It was discovered that this alloy displayed classical creep curve characteristics i...

This paper presents results from a research initiative aimed at investigating high temperature creep deformation mechanisms in Ni-base superalloys through a combination of creep experiments, TEM deformation mechanism characterization, and state of the art modeling techniques. The effect of microstructure on dictating creep rate controlling deformation mechanisms was revealed for specimens with ...

Recent seismological observations reveal the presence of seismic anisotropy in localized regions at the base of the mantle within an otherwise isotropic lower mantle. These regions can be placed in a tectonic context, corresponding to locations of paleosubduction and plume upwelling. This project works toward determining whether the observed seismic anisotropy may be explained by the developmen...

Long term tensile creep studies were conducted on binary NiAl in the temperature range 700-1200 K with the objectives of characterizing and understanding the creep mechanisms. Inverse and normal primary creep curves were observed depending on stress and temperature. It is concluded that the primary creep of NiAl is limited by dislocation mobility. The stress exponent for creep, n, decreased fro...

A steady-state creep law for rocksalt, describing the two parallel mechanisms of dislocation creep and fluid-enhanced grain-boundary diffusion creep, has been used in numerical models of salt diapirism, to study the effective viscosity of rocksalt. Typical models included a 3-km-thick sedimentary layer on top of 1 km of rocksalt. The grain size of the salt has been varied between 0.5 and 3 cm a...