It is shown by a crystallographic etching technique that deformation banding is an important deformation mode in copper. In a cold rolled coarse grain copper, deformation banding forms in a three dimensional manner dividing grains into a large number of bands of different orientations. The influence of this important, but long ignored deformation mode, is studied by incorporating it into the Ta...

We consider the simulation of deformation of polycrystalline materials by grain boundary diffusion creep. For a given network of grain boundaries intersecting at nodes, with appropriate boundary conditions, we can calculate the rate at which material will be dissolved or deposited along each grain boundary and hence predict the rate at which each grain will move to accommodate this dissolution/...

Pressure-induced structural transformations in spherical and faceted gallium arsenide nanocrystals of various shapes and sizes are investigated with a parallel molecular-dynamics approach. The results show that the pressure for zinc blende to rocksalt structural transformation depends on the nanocrystal size, and all nanocrystals undergo nonuniform deformation during the transformation. Spheric...

Carbide tungsten cobalt alloys were deformed in compression or in three point bending in a temperature range 1000-1350°C and in a stress domain 30-1000MPa. In these conditions, the stress exponent n of WC-CO alloys is a function of only the cobalt volurnic ratio and tends tow rds n = 1 for pure B carbide. The apparent activation energy is 550 kj mole. T.E.M. investigations on pure carbide defor...

Recent experimental studies on nanocrystalline metals have shown that mechanical strength may decrease with decreasing grain size d for d,10– 15 nm. The mechanisms underlying this trend are not understood, although such a relationship is in distinct contrast to that seen in microcrystalline metals whereby strength increases with decreasing grain size. Here, we present direct experimental observ...

The study reports the mechanical property and microstructure of cold rolled low carbon steel and its work-hardening behavior in the deformation process. The tensile test in room temperature of low carbon steel was implemented for the different cold rolling deformation, the stress-strain curve was draught according to the relationship between strength and deformation and fitted for the polynomia...

Capillarity-driven grain boundary (GB) motion in Al tricrystalline thin films has been investigated by in situ transmission electron microscopy at intermediate temperatures. The GBs were observed to move erratically, with alternating periods of motion and stagnation, followed by rapid shrinkage of the grain and eventual annihilation accompanied by the emission of dislocations. The absence of me...

A review on the microstructural evolution in magnesium alloys during severe plastic deformation waspresented. The challenges deserved to achieve ultrafine/ nanostructured magnesium were discussed.The characteristics of the processed materials are influenced by three main factors, including i)difficult processing at low temperatures, ii) high temperature processing and the occurrence ofdynamic r...

Superplastic structural ceramics (Y-TZP, A1203, Si3N4, and their composites) that can withstand biaxial stretching to large strains have been developed recently. Microstructural design of these ceramics first requires an ultrafine grain size that is stable against coarsening during sintering and deformation. A low sintering temperature is a necessary, but not a sufficient, condition for achievi...

A model to describe the role of grain boundaries in the overall response of a polycrystalline material at small length scales subject to finite deformations is presented. Three alternative thermodynamically consistent plastic flow relations on the grain boundary are derived and compared using a series of numerical experiments. The numerical model is obtained by approximating the governing relat...