scholarly journals Role of In-grain Shear Bands in the Nucleation of //ND Recrystallization Textures in Warm Rolled Steel.

1998 ◽  
Vol 38 (1) ◽  
pp. 78-85 ◽  
Author(s):  
M. R. Barnett
Keyword(s):  
Shear Bands ◽  
Rolled Steel

New  podiform chromitites Occurrence from the Masirah Ophiolite, Oman

2021 ◽  
Author(s):  
Sobhi Nasir
Keyword(s):  
Tectonic Setting ◽  
Shear Bands ◽  
Mineral Inclusions ◽  
Silicate Inclusions ◽  
Mid Ocean Ridge ◽  
Early Paleocene ◽  
Podiform Chromitites ◽  
Ocean Ridge ◽  
Mantle Section

<p>The Masirah ophiolite is one of the few true ocean ridge ophiolites that have been preserved (Rollinson, 2017) and lacks any indication that it formed in a subduction environment. The Masirah ophiolite in south-eastern Oman is a different and older ophiolite from the more famous northern Oman ophiolite. Chromite and copper ores comprise large deposits in the Samail ophiolite, northern Oman. In comparison, chromite and copper deposits have not been described in previous reports or previous exploration in Masirah ophiolite. Rollinson (2017) has proposed that the apparent absence of chromitites in the mantle section of Masirah ophiolite is an important discriminant between subduction related and ocean ridge ophiolites.  However, during recent studies on the Batain ophiolite mélange, and Masirah ophiolite, several chromitite pods have been discovered. The chromitites occur as separated small concordant, lenticular pods (3–10 m in thickness), which have been extensively altered and deformed, with the host pyroxenite serpentinites serpentinized harzburgites and dunites. The largest chromitite pods found within the pyroxenite and dunite of Masirah are up to 10 m across.  Unusual minerals and mineral inclusions (orthopyroxene, clinopyroxene, amphibole, phlogopite, serpentine, native Fe, FeO, alloy, sulfide, calcite, laurite, celestine and halite) within chromite have been observed in the chromitites from the  Masirah ophiolites.  The existence of hydrous silicate inclusions in the chromite calls for a role of hydration during chromite genesis. Both  phlogopite and hornblende were possibly formed from alkali-rich hydrous fluids/melts trapped within the chromite during the chromitite formation. High-T green hornblende and phlogopite included in the chromites is evidence of the introduction of water in the magma at the end of the chromite crystallization. Such paragenesis points to the presence of hydrous fluids during the activity of the shear bands. The chromitites parental magmas are rich in K, Na, LREE, B, Cs, Pb, Sr, Li, Rb and U relative to HREE, reflecting the alkalic fluids/melts that prevailed during the chromitites genesis.</p><p>The mineral inclusions  in association with host peridotites may have been brought by the uprising asthenosphere at mid-oceanic ridges due to the mantle convection. It appears that this chromite has been formed through reaction between amid-ocean-ridge basalt-melt with depleted harzburgite in the uppermost mantle.  The chromitite deposits have similar cr# (55-62% Al-chromitites), mg# Al2O3 and TiO2 contents to spinels found in MORB, and have been interpreted as having formed in amid-ocean ridge setting.  This suggests that this chromitites is residual from lower degree, partial melting of peridotite, which produced low-Cr# chromitites at the Moho transition zone, possibly in a mid-ocean-ridge setting. The chemistry of both mineral inclusions and chromite   suggests MORB-related tectonic setting for the chromitites that were crystallized at 1000 °C–1300 °C under pressures <3 GPa . The host peridotites were generated during the proto-Indian Ocean MORB extension and emplaced as a result of the obduction of the ophiolite over the Oman Continental margin during Late Cretaceous-Early Paleocene.</p><p>Rollinson, H., 2017. Geoscience Frontiers, 8: 1253–1262.</p>

scholarly journals Influence of Rare Earth Addition on Texture Development during Static Recrystallization and Mechanical Behaviour of Magnesium Alloy Sheets

2011 ◽  
Vol 702-703 ◽  
pp. 651-654
Author(s):  
Sang Bong Yi ◽  
Lilian Rayas ◽  
Stefanie Sandlöbes ◽  
Stefan Zaefferer ◽  
Dietmar Letzig ◽  
...  
Keyword(s):  
Rare Earth ◽  
Grain Growth ◽  
Static Recrystallization ◽  
Shear Bands ◽  
Rare Earth Addition ◽  
Axial Tensile ◽  
Sheet Formability ◽  
Cold Rolled ◽  
Basal Type

The role of rare earth addition on the microstructure and texture during recrystallization of cold rolled sheets is investigated by a comparative study of pure Mg, Mg-3Y and Mg1.5Nd sheets. In pure Mg, nucleation occurs mainly at shear bands which results in a texture weakening. The basal-type texture re-strengthens rapidly during grain growth of the pure Mg sheet. In contrast, in the Mg-RE alloys the weaker texture formed during early recrystallization strage is retained during further annealing due to retarded grain growth. Uni-axial tensile and Erichsen tests show that ductility and sheet formability are significantly improved by addition of rare earth elements.

scholarly journals Role of Glass Composition on Mechanical Properties of Shape Memory Alloy-Metallic Glass Composites

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Supat Chupradit ◽  
Indah Raya ◽  
Dinh Tran Ngoc Huy ◽  
Dmitry Bokov ◽  
Pham Van Tuan ◽  
...  
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Md Simulation ◽  
Shear Bands ◽  
Laminated Composite ◽  
Softening Effect ◽  
Glass Composites ◽  
Wide Range ◽  
Tension Loading

In this work, the molecular dynamics (MD) simulation was applied to design a laminated composite structure comprised of the shape memory alloy (SMA) and Cu-Zr metallic glasses (MGs). A wide range of MG compositions was considered to tune the mechanical features and improve the homogenous plastic deformation during the tension loading. The results indicated that the martensitic transformation in the SMA inhibited the sudden shear band propagation in the composite for all the samples. Moreover, it was revealed that the mechanism of plasticity was significantly affected by the change of MG composition. In the Cu-rich MGs, the formation and propagation of thick shear bands occurred at the end of the tension loading; however, the increase in Zr content induced the interaction of multiple shear bands with finer configurations in the system. Nevertheless, the excessive Zr addition in the MG composition facilitated the aggregation of nanopores at the interface of SMA and MGs, which may be due to the softening effect in the Zr-rich MGs. Finally, it is concluded that an optimized MG composition is required for the trade-off between the plasticity and the strength in the SMA-MG composites.

Deformation Structure and Texture Transformations in Twinned Fcc Metals: Critical Role of Micro- and Macro- Scale Shear Bands

2007 ◽  
Vol 550 ◽  
pp. 521-526 ◽  
Author(s):  
Henryk Paul ◽  
Julian H. Driver
Keyword(s):  
Shear Banding ◽  
Critical Role ◽  
Shear Bands ◽  
Fcc Metals ◽  
Macro Scale ◽  
Local Lattice ◽  
Textural Changes ◽  
Scale Shear ◽  
Sem Analyses

Microstructure and texture development in twinned fcc metals is investigated in order to characterize the influence of micro- and macro-scale brass-type shear bands (SB) on structural and textural changes at large deformations. TEM and SEM analyses are focused on bands developed by plane strain compression in twinned C{112}<111> oriented single crystals. The proposed crystallographic model of the shear banding phenomenon refers to the idea of local lattice reorientation within narrow areas. Most of these rotations occur around the TD||<110> axis with significant further rotations about <112> poles. These two rotations explain the influence of SB’s on the formation of Goss{110}<001> and brass{110}<112>-S{123}<634> texture components clearly observed in highly deformed low SFE metals. At high deformations symmetrically equivalent crystal lattice rotations inside narrow areas lead to the formation of positive and negative macroscopic SBs.

Deformation texture transition in brass: critical role of micro-scale shear bands

2000 ◽  
Vol 48 (10) ◽  
pp. 2665-2673 ◽  
Author(s):  
E. El-Danaf ◽  
S.R. Kalidindi ◽  
R.D. Doherty ◽  
C. Necker
Keyword(s):  
Critical Role ◽  
Shear Bands ◽  
Deformation Texture ◽  
Micro Scale ◽  
Texture Transition ◽  
Scale Shear

DEM Study on Energy Allocation Behavior in Crushable Soils

2013 ◽  
Vol 871 ◽  
pp. 119-123
Author(s):  
Jian Feng Wang ◽  
Run Qiu Huang
Keyword(s):  
Shear Bands ◽  
Constitutive Models ◽  
Energy Allocation ◽  
Particle Breakage ◽  
Large Strains ◽  
Detailed Knowledge ◽  
Soil Fabric ◽  
Specimen Density ◽  
Interparticle Friction

Detailed knowledge of particle-scale energy allocation behavior under the influence of particle breakage is of fundamental importance to the development of micromechanics-based constitutive models of sands. This paper reports original results of the energy input/dissipation of an idealized crushable soil using 3D DEM simulations. Particle breakage is modeled as the disintegration of synthetic agglomerate particles which are made up of parallel-bonded elementary spheres. Simulation results show that the initial specimen density and crushability strongly affect the energy allocation of the soil both at small and large strains. The major role of particle breakage, which itself only dissipates a negligible amount of input energy, is found to advance the soil fabric change and promote the interparticle friction dissipation. Particularly, at small strains, particle breakage disrupts the strain energy buildup and thus reduces the mobilized shear strength and dilatancy of a granular soil. At large strains where particle breakage is greatly reduced, a steady energy dissipation by interparticle friction and mechanical damping is observed. Furthermore, it is found that shear bands develop in most dense crushable specimens at large strains, but they are only weakly correlated to the anisotropy of the accumulated friction dissipation.

Modeling the Role of Microstructure on Shear Instability with Reference to the Formability of Automotive Aluminium Alloys

2006 ◽  
Vol 519-521 ◽  
pp. 183-190 ◽  
Author(s):  
David S. Wilkinson ◽  
Xin Jian Duan ◽  
Ji Dong Kang ◽  
Mukesh K. Jain ◽  
J. David Embury
Keyword(s):  
Aluminium Alloys ◽  
Particle Density ◽  
Shear Bands ◽  
Rolling Direction ◽  
Shear Instability ◽  
Fe Model ◽  
Intermetallic Particles ◽  
Automotive Sheet ◽  
Cast Alloys

This paper addresses the effect of microstructure on the formability of aluminium alloys of interest for automotive sheet applications. The bulk of this work has been on the alloy AA5754 – both conventional DC cast alloys and continuous cast alloys made by twin belt casting. It is known that alloys such as these contain Fe as a tramp impurity which results in Fe-based intermetallic particles distributed through microstructure as isolated particles and in stringers aligned along the rolling direction. It is thought that these particles are the cause, both of the reduced ductility that is observed as the Fe level rises, and the relatively poor formability of strip cast alloys, as compared with those made by DC cast. Conventional wisdom suggests that the reduction of ductility is due to the effect of particles as nucleating sites for damage. However, most studies show that these materials are resistant to damage until just before fracture. We now believe that effect is actually related to the development of shear bands in these materials. We present experimental data which supports this conclusion. We then show how the FE models we have developed demonstrate the role of shear instability on fracture and the role played by hard particles. We show how a unit cell approach can be used to incorporate the effect of particle density and morphology on shear localization in a way that includes statistical variability due to microstructural heterogeneity. This leads to a set of constitutive equations in which the parameters are distributed from one region to another. These are then fed into a macroscopic FE model at the level of the specimen or the component in order to determine the effect of microstructural variability on shear instability and ductility.

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