In this research, variant selection of martensite transformed from ultrafine-grained (UFG) austenite fabricated by accumulative roll bonding (ARB) process and subsequent annealing was investigated with respect tomorphology of parentaustenitic phase. The results show that the original shape of austenite grain is very effective factor in determiningthe preferred variants of martensite transformed...

the formation of nano/ultrafine grained ferrite in low carbon steels containing different amounts of niobiumwas investigated using thermomechanical treatment which consisted of annealing of 85% cold rolled martensite with different parameters. the specimens were characterized by optical and scanning electron microscopy and vickers hardness test. a lamellar dislocation cell structure was formed ...

the mechanical properties and microstructural developments of 321 stainless steel during thermomechanicalprocess were investigated. the repetitive cold rolling and subsequent annealing wereconducted to achieve nanocrystalline structure in an aisi 321 stainless steel. heavily cold rolling at−20°c was conducted to form martensite in metastable austenitic steel. the process was followed byannealin...

Al 5083 alloy powder was mechanically milled in liquid nitrogen to achieve a nanocrystalline (NC) structure having an average grain size of 50 nm with high thermal stability, and then consolidated by quasi-isostatic (QI) forging. The consolidation resulted in ultrafine grains (UFG) of about 250 nm, and the bulk material exhibited enhanced strength compared to conventionally processed Al 5083. T...

Ambient and cryogenic surface mechanical attrition treatments (SMAT) are applied to bcc iron plate. Both processes result in significant surface grain refinement down to the ultrafine-grained regime; the cryogenic treatment results in a 45% greater grain size reduction. However, the refined region is shallower in the cryogenic SMAT process. The tensile ductility of the grain size gradient remai...

We have investigated the effects of helium ion irradiation energy and sample temperature on the performance of grain boundaries as helium sinks in ultrafine grained and nanocrystalline tungsten. Irradiations were performed at displacement and non-displacement energies and at temperatures above and below that required for vacancy migration. Microstructural investigations were performed using Tra...

We present the results of in-situ studies of evolution of grain boundary misorientations in ultrafine grained (UFG) aluminum alloy Al-4 Cu-0.5 Zr (wt%) during annealing. The structure of the UFG alloy was obtained by severe plastic deformation method. Misorientations between the grains were measured using single reflection technique. It was found that relaxation processes during annealing are a...

Field ion microscopy and computer simulation were used for the study of an atomic structure high-angle grain boundary in hard-drawn ultrafine-grained tungsten wire. These boundaries with special misorientations are beyond the scope of the coincident site lattice model. It was demonstrated that the special non-coincident grain boundaries are the plane-matching boundaries, and rigid-body displace...

Micro-forming with ultrafine-grained (UFG) materials is a promising direction for the fabrication of micro-electro-mechanical systems (MEMS) components due to the improved formability, good surface quality, and excellent mechanical properties it provides. In this paper, micro-compression tests were performed using UFG pure aluminum processed by equal-channel angular pressing (ECAP) with subsequ...

An overview of micromechanical models of strength and deformation behaviour of nanostructured and ultrafine grained metallic materials is presented. Composite models of nanomaterials, polycrystal plasticity based models, grain boundary sliding, the effect of nonequilibrium grain boundaries and nanoscale properties are discussed and compared. The examples of incorporation of peculiar nanocrystal...