A new process to obtain ultrafine grained bulk steel was developed. Plain low-carbon steel sheet with martensite starting microstructure was simply cold-rolled by 50% and annealed. The specimens ...annealed at intermediate temperatures such as 773 K revealed the multiphased nano-structure and showed superior mechanical properties.
Formation process of ultrafine grained ferrite through a simple thermomechanical route composed of cold-rolling and annealing of dual-phase starting microstructures was investigated. A 0·1%C steel ...having a ferrite-martensite dual-phase microstructure was cold-rolled by 91% and subsequently annealed below the eutectoid (A1) temperature. During the annealing, the cold-rolled microstructure gradually changed to be equiaxed ultrafine ferrite, without preferential growth of particular ferrite grains. Hardness of the cold-rolled specimen continuously decreased without a significant drop. The main components of texture in the cold-rolled specimen, α-fibre and γ-fibre, did not change greatly after the formation of ultrafine grains. It was suggested that finely subdivided region having large misorientations in the cold-rolled state grew with recovery to form the ultrafine ferrite.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Through a method previously used on aluminum alloys, ultra-fine grained bulk steel (interstitial free (IF) steel) whose mean grain size is < 1 mu m has been successfully produced by Accumulative ...Roll-bonding (ARB) process which has been developed by us as a novel intense straining process using rolling deformation. The ultra-fine grained IF-steel with mean grain size of 420 nm showed very large tensile strength of 870 MPa, which is 3.1 times larger than that of the starting material. The change in mechanical properties and the microstructural evolution in the course of ARB process were quite similar to those in the Al alloys previously studied. The present results indicate that ARB is very useful process for high straining and ultra-grain refining, and most of structural metallic materials with ultra-fine grains could be easily achieved by ARB. Aluminum materials briefly discussed include 1100 pure Al and 5083 Al-Mg alloy.
In this study, the deformation behavior of two phases in a model dual phase system of copper and a martensitic stainless steel was investigated using in situ synchrotron X-ray diffraction. Due to the ...different crystallographic structures of copper and martensite, their diffraction patterns are well separated such that the strain distribution and the load partitioning between the phases could be investigated under loading using standard methods. The copper matrix started to yield at low stress levels after a short stage of elastic deformation and the different lattice strain of the copper and martensite indicated that load partitioning took place after yielding of the copper.
Spin selective magnetic hysteresis (SSMH) curves, orbital selective magnetic hysteresis (OSMH) curves and magnetic quantum number selective SSMH curves are obtained for CoFeB/MgO multilayer films by ...combining magnetic Compton profile measurements and superconducting quantum interference device (SQUID) magnetometer measurements. Although the SQUID magnetometer measurements do not show perpendicular magnetic anisotropy (PMA) in the CoFeB/MgO multilayer film, PMA behavior is observed in the OSMH and SSMH curves for the |m| = 2 magnetic quantum number states. These facts indicate that magnetization switching behavior is dominated by the orbital magnetization of the |m| = 2 magnetic quantum number states.
The effect of austenite grain size on kinetics of dynamic ferrite transformation above Ae3 in a 6Ni–0.1C steel was studied. As the austenite grain size decreased, the onset of dynamic transformation ...was accelerated. The increase in the fraction of dynamically transformed ferrite was in good agreement with the change in flow stress, i.e. dynamic softening. The kinetics of dynamic transformation could be evaluated by an Avrami-type formula.
Structure and strength after large strain deformation Hansen, N.; Huang, X.; Ueji, R. ...
Materials science & engineering. A, Structural materials : properties, microstructure and processing,
12/2004, Letnik:
387
Journal Article
Recenzirano
A detailed structural characterisation is the basis for an analysis of the structure–flow stress relationship in deformed metals. This is demonstrated for aluminium (99% purity) deformed to very ...large strain by cold rolling. The analysis is repeated for aluminium of similar purity deformed to large strains by accumulative roll bonding (ARB), which introduces a significantly different microstructure than that observed after cold rolling. The structure–flow stress relationship of ARB materials is discussed and related to that observed for cold rolled samples.
Abstract
This study revealed characteristics of the deformation behavior in high/medium entropy alloys (HEAs/MEAs) with face-centered cubic (FCC) structure. A Co
60
Ni
40
alloy and a Co
20
Cr
40
Ni
...40
MEA having low and high friction stresses (fundamental resistance to dislocation glide in solid solutions), respectively, but similar in other properties, including their stacking fault energy and grain sizes, were compared. The MEA exhibited a higher yield strength and work-hardening ability than those in the Co
60
Ni
40
alloy at room temperature. Deformation microstructures of the Co
60
Ni
40
alloy were composed of coarse dislocation cells (DCs) in most grains, and a few deformation twins (DTs) formed in grains with tensile axis (TA) nearly parallel to . In the MEA, three microstructure types were found depending on the grain orientations: (1) fine DCs developed in TA~// -oriented grains; (2) planar dislocation structures (PDSs) formed in grains with other orientations; and (3) dense DTs adding to the PDSs developed in TA~// -oriented grains. The results imply difficulty in cross-slip of screw dislocations and dynamic recovery in the MEA, leading to an increase in the dislocation density and work-hardening rate. Our results suggest that FCC high-alloy systems with high friction stress inherently develop characteristic deformation microstructures advantageous for achieving high strength and large ductility.
The role of shear strain on ultragrain refinement of aluminum during accumulative roll-bonding (ARB) process was studied. The complicated distribution of redundant shear strain through thickness of ...the ARB processed sheets was quantitatively shown first, and good correspondence between the grain size and the amount of shear strain was found.
Temperature dependent experimental Compton profiles of quaternary alloys Co1−xCuxMnSb (x = 0.0, 0.2, 0.6 and 0.8) when decomposed into constituent profiles show that the sp-electron spin ...polarization is antiferromagnetically coupled to Mn-3d moments. The orbital magnetic moments derived from combination of magnetic Compton profiles (MCPs) and magnetization measurements are found to be small. Moreover, the first-principles full potential-linearized augmented plane wave (FP-LAPW) calculations have been performed to validate the experimental investigations of spin moments and half-Heusler properties. Present experimental and theoretical work show major role of Mn atoms in building-up the absolute spin moments. Our MCP data and spin-projected density of states derived from FP-LAPW computations show an increase in sp-d interaction in conduction region on increasing the Cu concentration. Further, Ruderman-Kittel-Kasuya-Yosida-type hybridization and antiferromagnetic superexchange interactions are witnessed in the reported alloys.
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