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At least 397 records · Page 22

Origin of the {111}〈112〉 Cold Rolling Texture Development in a Soft Magnetic Fe-27%Co Alloy

Plastic deformation of Fe-27%Co alloy at room temperature was investigated. The present alloy, usually delivered with a low-texture component for the magnetic core in rotating machines, develops a rather high intensity of Goss texture after recrystallization, when a suitable manufacturing process is applied. Thanks to this texture and its magnetic properties, this material can replace the grain-oriented Fe-3%Si alloy in electric transformer application. The intensity of the recrystallization Goss component depends directly on the sharpness of the {111}〈112〉 orientation developed during cold rolling. Thus, the origin of this {111}〈112〉 deformation texture has been studied using visco-plastic self-consistent (VPSC) simulations. This model showed that only the {110}〈111〉 slip systems allow developing the {111}〈112〉 texture. The predominance of this slip system has been effectively identified from slip markings on the deformed sample by EBSD. More, this simulation has shown that a Goss texture at the hot-rolled state favors the {111}〈112〉 development during cold rolling, as observed experimentally.

36 MATERIALS SCIENCE↗

Effect of Anisotropy on Microstructures and Mechanical Properties of Rolled Ti/Al/Mg/Al/Ti Laminates

TA2/5052Al/AZ31/5052Al/TA2 five-ply laminates were fabricated by hot rolling, and the effect of anisotropy on their microstructures and mechanical properties was studied. After rolling, the Mg/Al and Al/Ti interfaces were both closely connected, but the interfacial shapes were totally different. For the Mg layer microstructures in the middle area, regardless of the direction, dynamic recrystallized (DRXed) grains appeared around the deformation bands. However, twins and a shear zone appeared in the RD sample; the twins decreased in the sample along the 45° angle, and no twins appeared in the TD sample. The Ti layer showed equiaxed grains in different directions, which were attributed to the ability of Ti alloy to anti-deform. The tensile testing results showed that the fracture of the Ti/Al/Mg/Al/Ti laminates can be divided into four stages. The laminate had an ultimate tensile strength of 434 MPa and excellent elongation along the rolling direction (RD), which were attributed to its DRXed grains and twins. In conclusion, the laminates had significant anisotropy due to the presence of Mg alloys.

36 MATERIALS SCIENCE↗

Effect of Electropulsing on Surface Mechanical Behavior and Microstructural Evolution of Inconel 718 during Ultrasonic Surface Rolling Process

In the current study, the surface mechanical behavior and microstructural evolution of Inconel 718 superalloy processed by the ultrasonic surface rolling process (USRP) and electropulsing-assisted ultrasonic surface rolling process (EP-USRP) were carefully analyzed. The experimental results suggested that after EP-USRP with a frequency of 400 Hz, significant enhancements in Vickers microhardness and nanoindentation hardness were achieved compared to those of USRP specimens, with increases of 13.6 and 9.9%, respectively. Moreover, the machined surface quality, wear resistance, and thermal stability were also improved after EP-USRP (400 Hz). These enhancements in mechanical behavior are closely related to the microstructural evolution induced by electropulsing. Under the coupling of thermal and athermal effects of high-energy electropulsing, the deformation limit of USRP is surpassed and a new balance is achieved between the electropulsing softening effect and the ultrasonic rolling hardening effect. Therefore, further grain refinement, improved plastic deformation ability in the strengthened layer, and the interaction effect between nano-sized precipitates and grain boundaries are probably the main reasons for these results.

36 MATERIALS SCIENCE↗

Influence of rolling reduction and annealing on recrystallization and grain structure in Ta-2.5W alloys

The microstructural evolution of wrought Tantalum - 2.5 wt% Tungsten (Ta-2.5W) alloys during thermomechanical processing is critical for optimizing their mechanical reliability in demanding applications such as aerospace, chemical processing, and nuclear technology. Despite the widespread use of Ta-W alloys, a comprehensive understanding of how rolling reduction, annealing temperature, and elemental inhomogeneity interact to determine recrystallization behavior and grain refinement remains incomplete. Here, in this study, we systematically investigate the effects of cold rolling and subsequent annealing on the microstructure of Ta-2.5W, with particular attention to grain orientation, stored energy, and elemental banding. Our results demonstrate that higher rolling reduction rates lower the onset and completion temperatures for recrystallization, resulting in finer and more homogeneous grain structures. Electron backscatter diffraction (EBSD) analysis reveals that grains with a 〈111〉 parallel to the plate normal possess higher stored energy and nucleate recrystallization more readily than grains with a 〈001〉 parallel to the plate normal. Elemental mapping shows that tungsten inhomogeneity leads to localized bands of accelerated recrystallization and hardness variation. These findings provide new insights into the mechanisms of microstructure refinement in Ta-2.5W alloys, offering guidance for tailoring processing routes to achieve superior performance in demanding engineering environments.

Annealing↗

Tensile properties of co-rolled Zr/U-10Mo fuel at ambient and elevated temperatures

The United States High Performance Research Reactor (USHPRR) initiative is currently interested in replacing high-enriched uranium fuel in research reactors with high-assay low-enriched uranium fuel. Here, this work aimed to assist in that mission by providing tensile and bend test data on bare U-Mo and tensile test data on co-rolled Zr/U-10Mo plates at differing thicknesses (0.285 mm, 0.300 mm, and 0.465 mm) and temperatures (293 K, 473 K, and 623 K). Yield strength and ultimate tensile strength values are reported along with an in-depth comparison of how temperature, rolling direction, thickness, and the presence of the Zr-interlayer affect mechanical properties. Results showed that yield strength and ultimate tensile strength in Zr/U-10Mo foils lower as temperature increases by approximately 300 MPa from 293 to 473 K, and another 100 MPa from 473 to 623 K. Additionally it was found that with increased temperature, there is less differentiation in fuel necking and delamination behavior, as well as a greater perceived elongation to fracture. The elastic modulus of co-rolled mini-plates does not follow the volumetric rule of mixtures in terms of averaged strength and is actually lower than the reported moduli of both Zr and U-10Mo.

11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

An EBSD investigation of cryogenically-rolled Cu–30%Zn brass

Electron backscatter diffraction was used to study grain structure development in heavily cryogenically-rolled Cu–30%Zn brass. The produced microstructure was found to be very inhomogeneous. At a relatively coarse scale, it consisted of texture bands having crystallographic orientations close to the α- and γ-fibers. The texture bands contained internal structure comprising shear bands, mechanical twins, and low-angle boundaries. Such features were more pronounced within the γ-fiber, and this resulted in a heterogeneous ultrafine grain structure. The cryogenic rolling was concluded to be not straightforward for production of nanocrystalline grain structure in Cu–30%Zn brass. - Highlights: • Cryogenic rolling produced an inhomogeneous ultrafine-grained microstructure. • Grain refinement was mainly related with twinning and shear banding. • Grain refinement preferentially occurred in (111) fiber texture.

36 MATERIALS SCIENCE↗

Austenite stabilization and high strength-elongation product of a low silicon aluminum-free hot-rolled directly quenched and dynamically partitioned steel

Microstructures composed of lath martensite and retained austenite with volume fraction between 8.0 vol.% and 12.0 vol.% were obtained in a low-C low-Si Al-free steel through hot-rolling direct quenching and dynamical partitioning (HDQ&DP) processes. The austenite stabilization mechanism in the low-C low-Si Al-free steel under the special dynamical partitioning processes is investigated by analyzing the carbon partition behavior from martensite to austenite and the carbide precipitation-coarsening behavior in martensite laths combining with the possible hot rolling deformation inheritance. Results show that the satisfying retained austenite amount in currently studied low-Si Al-free HDQ&DP steel is caused by the high-efficiency carbon enrichment in the 30–80 nm thick regions of austenite near the interfaces in the hot-rolled ultra-fast cooled structure and the avoidance of serious carbides coarsening during the continuous cooling procedures. The excellent strength-elongation product reaching up to 26,000 MPa% shows that the involved HDQ&DP process is a promising method to develop a new generation of advanced high strength steel. - Highlights: • HDQ&DP processes were applied to a low-C low-Si Al-free steel. • Effective partitioning time during the continuous cooling processes is 1–220 s. • Retained austenite with volume fraction between 8.0 vol. % and 12.0 vol. % has been obtained. • The special austenite stabilization mechanism has been expounded.

36 MATERIALS SCIENCE↗

The evolution with strain of the stored energy in different texture components of cold-rolled IF steel revealed by high resolution X-ray diffraction

During the deformation of low carbon steel by cold-rolling, dislocations are created and stored in grains depending on local crystallographic orientation, deformation, and deformation gradient. Orientation dependent dislocation densities have been estimated from the broadening of X-ray diffraction lines measured on a synchrotron beamline. Different cold-rolling levels (from 30% to 95% thickness reduction) have been considered. It is shown that the present measurements are consistent with the hypothesis of the sole consideration of screw dislocations for the analysis of the data. The presented evolutions show that the dislocation density first increases within the α fiber (=(hkl)<110>) and then within the γ fiber (=(111) ). A comparison with EBSD measurements is done and confirms that the storage of dislocations during the deformation process is orientation dependent and that this dependence is correlated to the cold-rolling level. If we assume that this dislocation density acts as a driving force during recrystallization, these observations can explain the fact that the recrystallization mechanisms are generally different after moderate or large strains. - Highlights: • Dislocation densities are assessed by XRD in main texture components of a steel sheet. • Dislocation densities vary with both strain and texture components. • The analysis relies on the sole presence of screw dislocations. • The measured dislocation densities include the contribution of both SSD and GND.

36 MATERIALS SCIENCE↗

Thermal etching of silver: Influence of rolling defects

Silver is well known to be thermally etched in an oxygen-rich atmosphere and has been extensively studied in the laboratory to understand thermal etching and to limit its effect when this material is used as a catalyst. Yet, in many industrial applications the surface of rolled silver sheets is used without particular surface preparation. Here, it is shown by combining FIB-tomography, FIB-SIMS and analytical SEM that the kinetics of thermal etch pitting are significantly faster on rolled Ag surfaces than on polished surfaces. This occurs due to range of interacting phenomena including (i) the reaction of subsurface carbon-contamination with dissolved oxygen to form pores that grow to intersect the surface, (ii) surface reconstruction around corrosion pits and surface scratches, and (iii) sublimation at low pressure and high temperature. A method to identify subsurface pores is developed to show that the pores have (111) and (100) internal facets and may be filled with a gas coming from the chemical reaction of oxygen and carbon contamination. - Highlights: Thermal etching of industrial silver sheets vs. polished silver sheets Effect of annealing atmosphere on the thermal etching of silver: surface and subsurface characterization Link between etch pitting and defects induced by rolling. FIB-tomography coupled with EBSD for determining crystal planes of the facets of subsurface pores. FIB-SIMS characterization to probe the gas confined inside subsurface pores.

36 MATERIALS SCIENCE↗

Interface-correlated bonding properties for a roll-bonded Ti/Al 2-ply sheet

Highlights: • The feasible post roll-bonding annealing condition of Ti/Al clad was deduced. • The optimum thickness of the TiAl{sub 3} IMC diffusive layer is about 200 nm. • A ‘zipper-like’ failure mode at the interface yields the maximum bonding strength. - Abstract: We investigated the influence of annealing conditions on the interface-correlated microstructural evolution and subsequent bonding properties of a warm roll-bonded Ti/Al clad sheet. A TiAl{sub 3} intermetallic compound layer with a thickness of 160 nm was initially generated at the joint interface between the Ti and Al alloys by warm rolling. When the annealing time and temperature were increased to a maximum of 6 h and 650 °C, respectively, the thickness of the TiAl{sub 3} layer increased to 320 nm. The feasible annealing conditions for the optimum bonding strength were within 550 °C-6 h and 600 °C-3 h. An improvement in the bonding strength between Ti and Al is strongly correlated with the generation of considerable metallurgical bonding. This is manifested in the zipper-like failure mode that occurs at the TiAl{sub 3} joint interface for a layer thickness of less than 300 nm.

36 MATERIALS SCIENCE↗

Continuous microstructure evolution of ball rolled TWIP Ti15Mo alloy and its effect on phase precipitation behavior

Highlights: • Gradient microstructure was induced by ball rolling method in a Ti15Mo alloy. • Twin density increased and then decreased as increasing distance from surface. • Ultrafine (α + β) duplex structure was formed in the heavily deformed region. • α-phase in plate was precipitated in twined region in slightly deformed region. • Strengthening by formation of sub/nano-grains was notable than that by twins. - Abstract: A β-type Ti15Mo alloy with {332}<113> twinning-induced plasticity (TWIP) effect was utilized to investigate the continuous microstructure evolution of β-matrix by ball rolling method. Precipitation behavior of α-phase and strengthening mechanism were examined in regions with different strain. Amounts of intersected twins were present in the slightly deformed region of β-matrix, and their area fraction decreased with an increase of distance from rolled surface. The β-matrix close to surface was heavily deformed to result in the formation of abundant subgrains and nanograins, which was caused by cooperative occurrence of twinning refinement, intragranular dislocation activities and subgrain rotation. Mechanical twins provided the preferential nucleation sites for plate-like α-phase with strong variant selection. Equiaxed α-phase preferentially nucleated at the boundaries of subgrains and nanograins with weak variant selection to form the ultrafine (α + β) duplex structure. Due to the formation of subgrains and nanograins as well as the strain hardening, strengthening became more significant than that by twinning refinement solely. Similarly, the ultrafine (α + β) duplex structure exhibited a better strengthening effect than that by precipitation of plate-like α-phase. The diversities of deformation microstructure combined with different precipitation behaviors of α-phase are desirable for controlling the mechanical properties of β-type TWIP titanium alloys.

36 MATERIALS SCIENCE↗

Enhanced mechanical properties of carbon-doped FeNiMnAlCr high entropy alloy via hot-rolling

This work demonstrates an improvement in the mechanical performance of the high entropy alloy Fe 40.4 Ni 11.3 Mn 34.8 Al 7.5 Cr 6 containing 1.1 at. % carbon (CHEA) by hot-rolling followed by annealing at 1323 K. The microstructure was examined using scanning electron microscopy, electron backscatter diffraction, X-ray diffraction, and transmission electron microscopy. Room-temperature tensile tests were used to assess the alloy's mechanical properties. The presence of dense dislocation walls indicate that the alloy has not fully recrystallized and, moreover, the deformation substructure and the large fraction of Σ3 twin boundaries contribute to the high room temperature yield strength (~523 MPa). Despite the presence of substantial dislocation density, the annealed, hot-rolled CHEA displays an improvement in elongation to fracture (~33%) compared to the negligible ductility (< 2%) observed for the alloy after it has been simply annealed. Finally, the present work shows that hot rolling can produce good strength and ductility in the alloy while establishing the processing conditions necessary for the large-scale manufacture and utilization of its remarkable properties.

36 MATERIALS SCIENCE↗

Why does a phosphonium-phosphinate ionic liquid protect the contact surfaces from wear and micropitting but increase vibration when used as an additive in rolling-sliding lubrication?

A phosphonium-phosphinate ionic liquid (IL) was studied as a lubricant additive for rolling-sliding contacts. The bench-scale test was designed to simulate automotive rear axle operation during cold start, highway towing, and overload conditions. Adding such an IL (2%) into a base oil significantly reduced wear loss and rolling contact fatigue, e.g., microcracking and micropitting, but made the vibrational noise notably higher under a low (-1.5%) sliding roll ratio (SRR). Additionally, worn surface characterization revealed an interesting texture pattern with alternating smoother plateaus and rougher valleys, which is believed to cause the high vibration. No increased vibration was observed at a high (-30%) SRR, possibly because the more aggressive sliding abrasion prevented such a surface texture from forming.

36 MATERIALS SCIENCE↗

Evidence of a rolling motion of a microparticle on a silicon wafer in a liquid environment

The interaction of micro- and nanometer-sized particles with surfaces plays a crucial role when small-scale structures are built in a bottom-up approach or structured surfaces are cleaned in the semiconductor industry. For a reliable quantification of the interaction between individual particles and a specific surface, however, the motion type of the particle must be known. We developed an approach to unambiguously distinguish between sliding and rolling particles. To this end, fluorescent particles were partially bleached in a confocal laser scanning microscope to tailor an optical inhomogeneity, which allowed for the identification of the characteristic motion pattern. For the manipulation, the water flow generated by a fast moving cantilever-tip of an atomic force microscope enabled the contactless pushing of the particle. We thus experimentally evidenced a rolling motion of a micrometer-sized particle directly with a fluorescence microscope. A similar approach could help to discriminate between rolling and sliding particles in liquid flows of microfluidic systems.

42 ENGINEERING↗

Texture development during rolling of α+β dual-phase ZrNb alloys - 2016-0070

The texture evolution during high-temperature rolling (800 deg. C) of two model zirconium-niobium alloys was studied using electron backscatter diffraction. The aim was to decouple the relative importance of deformation and phase transformation on the final texture in an effort to elucidate the origin of the strong α-transverse basal texture commonly found in the hot-rolled product. The analysis uses a reconstruction software based on the Burgers relation to reconstruct the high-temperature β orientations, with the indexed α as input. In the low niobium content alloy, the texture evolution of the {11 2-bar 0}<10 1-bar 0> component was consistent with deformation in both α and β phases, along with a variant selection mechanism that occurred during the β → α phase transformation. Variant selection was observed to depend on the orientation of the deformed prior β grains. In the high niobium content alloy, a lower α volume fraction during hot rolling gave rise to different β textures and promoted the formation of a Goss component. This contributed to the {11 2-bar 0} <10 1-bar 0> component upon cooling, with variant selection enhanced by anisotropic grain breakup. (authors)

36 MATERIALS SCIENCE↗

Distinct Recrystallization Pathways in a Cold-Rolled Al-2%Mg Alloy Evidenced by In-Situ Neutron Diffraction

The time-of-flight neutron diffraction data collected in-situ on Oak Ridge National Laboratory’s (ORNL, Oak Ridge, TN, USA) VULCAN and Los Alamos National Laboratory’s (LANL, Los Alamos, NM, USA) High-Pressure-Preferred-Orientation (HIPPO) diffractometers have been analyzed complementarily to show the texture evolution during annealing of a cold-rolled Al-2%Mg alloy. The texture analysis aimed to identify the components present in the initial rolling (or deformation) texture and in the thermally-activated recrystallization texture, respectively. Using a quasi-Monte-Carlo (QMC) approach, a new method has been developed to simulate the weighted texture components, and to obtain inverse pole figures for both rolling and normal directions. As such, distinct recrystallization pathways during annealing in isochronal conditions, can be revealed in terms of the evolution of the texture components and their respective volume fractions. Moreover, the recrystallization kinetics associated with the cube and random texture components are analyzed quantitatively using a similar approach developed for differential scanning calorimetry (DSC).

36 MATERIALS SCIENCE↗

Baryogenesis from ultra-slow-roll inflation

The ultra-slow-roll (USR) inflation represents a class of single-field models with sharp deceleration of the rolling dynamics on small scales, leading to a significantly enhanced power spectrum of the curvature perturbations and primordial black hole (PBH) formation. Such a sharp transition of the inflationary background can trigger the coherent motion of scalar condensates with effective potentials governed by the rolling rate of the inflation field. We show that a scalar condensate carrying (a combination of) baryon or lepton number can achieve successful baryogenesis through the Affleck-Dine mechanism from unconventional initial conditions excited by the USR transition. Viable parameter space for creating the correct baryon asymmetry of the Universe naturally incorporates the specific limit for PBHs to contribute significantly to dark matter, shedding light on the cosmic coincidence problem between the baryon and dark matter densities today.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗