There has been considerable success over the past five decades in developing a phenomenological and micromechanism-based understanding of lastic flow, creep and superplasticity. Although it is widely known that grain sizes have a distribution in polycrystals and nanocrystals, this factor s usually not included in most analysis of deformation and failure. Experimental observations relating to th...

A new statistical theory is introduced that takes into account the coupling between grain size, shape and crystallographic texture during deformation of polycrystalline microstructures. A “grain size orientation distribution function” (GSODF) is used to encode the probability density of finding a grain size D along a direction (given by unit vector n) in grains with orientation g. The GSODF is ...

The grain size refinement of AISI 422 martensitic stainless steel in the temperature range of 950-1150 ºC was investigated by hot deformation tests. The deformed specimens were held at deformation temperature with delay times of 5 to 300s after achieving a strain of 0.3. The austenite grains exhibit a considerable growth at temperature higher than 1050˚C, while the grain coarsening is negligibl...

The effect of austenite grain size on the evolution of the bainite transformation in steels is not yet certain in spite of many investigations.1–7 Barford and Owen1 reported that the reaction rate was accelerated by decreasing the grain size, because of an increase in the number density of grain boundary nucleation sites. Umemoto et al.2 reported similar results and proposed an equation that de...

An analysis of snow grain size behavior with respect to other snow parameters such as snow depth, density, and temperature was performed. From this analysis, a pattern was derived which can be used to approximate the range of grain size variations. Data used in this research are from NASA Cold Land Processes Field Experiment (CLPX) in Colorado. This intensive field survey was conducted in Febru...

accumulative roll-bonding (arb) is a severe plastic deformation process that is using rolling to produce ultrafine grains in coarse grained metallic materials. in this study, arb has been applied on 70/30 brass up to 6 cycles at ambient temperature and non-lubricated conditions to apply a true strain up to 4.8 von mises strain. microstructures of arbed brass samples were characterized by scanni...

in order to investigate the contribution of ear photosynthesis and cytokinin in determining grain sink size, a pot study was conducted during january to june 2005 in cereal glasshouse of faculty of agriculture of karaj, iran. experiment was conducted in a complete randomized design with a factorial arrangement of two factors, three replications and four pots in each plot. factors included culti...

Based on the analysis of Poisson equation, an analytical threshold voltage model including quantum size effect of nc-TFTs (nanocrystalline silicon thin film transistor) has been proposed in this paper. The results demonstrate that the proposed simplified expression of threshold voltage agree perfectly with numerical calculation. The threshold voltage in nc-TFTs strongly depends on the size of s...

A PM approach is investigated in the context of extremely fine low temperature bainitic steels with a reasonable combination of ultimate tensile strength and uniform elongation. The strategy consists of three steps. First, ball milling is used for mechanical alloying and to create a large density of interfaces prior to sintering. In the second step, spark plasma sintering is used as a rapid con...

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...