scholarly journals Unique transition of yielding mechanism and unexpected activation of deformation twinning in ultrafine grained Fe-31Mn-3Al-3Si alloy

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yu Bai ◽  
Hiroki Kitamura ◽  
Si Gao ◽  
Yanzhong Tian ◽  
Nokeun Park ◽  
...  
Keyword(s):  
Grain Refinement ◽  
Twip Steel ◽  
Deformation Twinning ◽  
Ultrafine Grain ◽  
Yield Drop ◽  
Grain Sizes ◽  
Deformation Twins ◽  
Ultrafine Grained ◽  
The Mean

AbstractTensile mechanical properties of fully recrystallized TWIP steel specimens having various grain sizes (d) ranging from 0.79 μm to 85.6 μm were investigated. It was confirmed that the UFG specimens having the mean grain sizes of 1.5 μm or smaller abnormally showed discontinuous yielding characterized by a clear yield-drop while the specimens having grain sizes larger than 2.4 μm showed normal continuous yielding. In-situ synchrotron radiation XRD showed dislocation density around yield-drop in the UFG specimen quickly increased. ECCI observations revealed the nucleation of deformation twins and stacking faults from grain boundaries in the UFG specimen around yielding. Although it had been conventionally reported that the grain refinement suppresses deformation twinning in FCC metals and alloys, the number density of deformation twins in the 0.79 μm grain-sized specimen was much higher than that in the specimens with grain sizes of 4.5 μm and 15.4 μm. The unusual change of yielding behavior from continuous to discontinuous manner by grain refinement could be understood on the basis of limited number of free dislocations in each ultrafine grain. The results indicated that the scarcity of free dislocations in the recrystallized UFG specimens changed the deformation and twinning mechanisms in the TWIP steel.

High Speed Deformation of Ultrafine Grained TWIP Steel

2007 ◽  
Vol 561-565 ◽  
pp. 107-110 ◽  
Author(s):  
Rintaro Ueji ◽  
Kenji Harada ◽  
Noriyuki Tsuchida ◽  
Kazutoshi Kunishige
Keyword(s):  
Strain Rate ◽  
High Speed ◽  
Twip Steel ◽  
Ultrafine Grain ◽  
Grain Sizes ◽  
Ultrafine Grain Size ◽  
Ultrafine Grained ◽  
Wide Range ◽  
Twip Steels ◽  
Large Work

Tensile properties of twinning induced plasticity (TWIP) steels (31%Mn-3%Al-3%Si-Fe) with various mean grain sizes ranging from ultrafine grain size (1.1μm) to conventional one (35.5μm) at a wide range of strain rates from 10-3sec-1 to 103sec-1 were studied. The ultrafine grained TWIP steel exhibits a large work hardening and keeps an adequate elongation at any strain rate. The strength held to the Hall-Petch relationship at each strain rate and the Hall-Petch slopes do not change largely.

scholarly journals Grain Refinement of Ti-15Mo-3Al-2.7Nb-0.2Si Alloy with the Rotation of TiB Whiskers by Powder Metallurgy and Canned Hot Extrusion

Metals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 126 ◽  
Author(s):  
Jiabin Hou ◽  
Lin Gao ◽  
Guorong Cui ◽  
Wenzhen Chen ◽  
Wencong Zhang ◽  
...  
Keyword(s):  
Powder Metallurgy ◽  
Tensile Test ◽  
Grain Refinement ◽  
Hot Extrusion ◽  
Dislocation Motion ◽  
Continuous Dynamic Recrystallization ◽  
Grain Sizes ◽  
The Matrix ◽  
Continuous Dynamic

In situ synthesized TiB whiskers (TiBw) reinforced Ti-15Mo-3Al-2.7Nb-0.2Si alloys were successfully manufactured by pre-sintering and canned hot extrusion via adding TiB2 powders. During pre-sintering, most TiB2 were reacted with Ti atoms to produce TiB. During extrusion, the continuous dynamic recrystallization (CDRX) of β grains was promoted with the rotation of TiBw, and CDRXed grains were strongly inhibited by TiBw with hindering dislocation motion. Eventually, the grain sizes of composites decreased obviously. Furthermore, the stress transmitted from the matrix to TiBw for strengthening in a tensile test, besides grain refinement. Meanwhile, the fractured TiBw and microcracks around them contributed to fracturing.

Synthesis, characterization, and properties of nanophase TiO2

1988 ◽  
Vol 3 (6) ◽  
pp. 1367-1372 ◽  
Author(s):  
R. W. Siegel ◽  
S. Ramasamy ◽  
H. Hahn ◽  
L. Zongquan ◽  
L. Ting ◽  
...  
Keyword(s):  
Sintering Temperature ◽  
Positron Annihilation Spectroscopy ◽  
Sintering Aids ◽  
Gas Condensation ◽  
Grain Sizes ◽  
Transmission Electron ◽  
Ultrafine Grained ◽  
Conventional Sintering ◽  
Hardness Values

Ultrafine-grained, nanophase samples of TiO2 (rutile) were synthesized by the gas-condensation method and subsequent in situ compaction. The samples were studied by a number of techniques, including transmission electron microscopy, Vickers microharness measurements, and positron annihilation spectroscopy, as a function of sintering temperature. The nanophase compacts with average initial grain sizes of 12 nm were found to densify rapidly above 500 °C, with only a small increase in grain size. The hardness values obtained by this method are comparable to or greater than those for coarser-grained compacts, but are achieved at temperatures 400 to 600 °C lower than conventional sintering temperatures and without the need for sintering aids.

Shock deformation twinning in molybdenum and a comparison of deformation twinning in shock-loaded BCC and FCC metals

1978 ◽  
Vol 36 (1) ◽  
pp. 590-591
Author(s):  
L.E. Murr ◽  
K. Wongwiwat
Keyword(s):  
Pulse Duration ◽  
Shock Loading ◽  
Impedance Matching ◽  
Deformation Twinning ◽  
Loading Test ◽  
Fcc Metals ◽  
Grain Sizes ◽  
Shock Deformation ◽  
Deformation Twins ◽  
Matching Techniques

Verbraak reported deformation twins to have been formed in shock-loaded molybdenum from observations by optical metallography. Attempts to verify the existence of deformation twins in shock-loaded molybdenum by Murr, et al. were unsuccessful at pressures ranging up to 21 GPa (210 kbars) at a constant pulse duration of 2 μs. Since the conditions under which Verbraak originally observed deformation twins were not well documented, a study was undertaken to reinvestigate the shock deformation of molybdenum in a range of pressures and pulse durations.Molybdenum sheets (0.0025 cm thick and 0.025 cm thick) were annealed to produce several grain sizes and shock loaded in molybdenum sandwiches and assemblies (spall plates and momentum traps) by impacting them with stainless steel flyer plates as outlined previously. Pressure experiments were performed at 140, 260, and 350 kbars (corrected pressure values using impedance matching techniques) at a constant pulse duration of 2 μs while two additional experiments were conducted at 260 kbars by shock loading test assemblies at pulse durations of 0.5 μs and 8 μs.

Dynamic energy absorption of ultrafine-grained TWIP steel under axial impact loading

2018 ◽  
Vol 1 (1) ◽  
pp. 51-64 ◽  
Author(s):  
Mahmoud H. A. Gadelhaq ◽  
Atef S. Hamada ◽  
Mohsen A. Hassan ◽  
Jukka Kömi
Keyword(s):  
Energy Absorption ◽  
Twip Steel ◽  
Cast Steel ◽  
Tensile Tests ◽  
High Yield ◽  
Ultrafine Grain ◽  
Recrystallization Annealing ◽  
Ultrafine Grained ◽  
Cold Worked ◽  
The Impact

This research focuses on studying the dynamic energy absorption property of a micro-alloyed TWIP steel, which was proposed to act as a connection part between car front bumper and chassis in middle-class cars for vehicle safety. The studied TWIP steel was designed based on stacking fault energy of 25mJ/m2. The as-cast steel was deformed in hot and cold rolling to 2 mm thick sheets. Subsequently, recrystallization annealing was applied to the heavily cold-worked steel at different temperatures to obtain different ultrafine grain structures. The mechanical properties were determined using tensile tests. It was observed that at 900°C, the optimal temperature for strengthening by vanadium carbide precipitation, it was too low to complete recrystallization. However, at 1000°C, an ultrafine-grained structure was formed with high yield, tensile strengths and elongation of about 700MPa, 1100MPa and 30% respectively. Accordingly, TWIP steel was used for crash analysis simulation using ANSYS Workbench R14.5. Thin-walled square columns of that steel were employed for energy absorbance during a collision regarding progressive plastic deformation. The crashworthiness criteria were studied under different impact conditions with thicknesses of 0.25, 0.5, 0.75 and 1 mm. Simulation results showed high initial peak force during the impact. Hence, a trigger mechanism of an external tapered plunger was proposed to reduce it. This combination of new material and innovative design promises enhancement car safety.

Developing High Strain Rate Superplasticity in Aluminum Alloys

2005 ◽  
Vol 475-479 ◽  
pp. 2949-2954 ◽  
Author(s):  
Cheng Xu ◽  
Minoru Furukawa ◽  
Z. Horita ◽  
Terence G. Langdon
Keyword(s):  
Elevated Temperatures ◽  
High Strain ◽  
Superplastic Forming ◽  
Ultrafine Grain ◽  
Strain Rates ◽  
Cast Aluminum ◽  
Grain Sizes ◽  
Angular Pressing ◽  
Ultrafine Grained ◽  
Materials Used

The conventional materials used in superplastic forming operations generally have grain sizes of ~2 µm or larger and they exhibit superplasticity at relatively low strain rates. Processing by equal-channel angular pressing (ECAP) produces materials having ultrafine-grain sizes, usually in the submicrometer range. If these ultrafine grains show reasonable stability at elevated temperatures, the alloys may exhibit a capability for achieving superplastic elongations at high strain rates. This paper examines the development of ultrafine-grained structures and superplastic ductilities in a spray-cast aluminum 7034 alloys through ECAP. The results show that ECAP is a very effective procedure for achieving grain refinement and superplasticity at rapid strain rates.

scholarly journals Interactions between Dislocations and Boundaries during Deformation

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 1012
Author(s):  
Hongjiang Pan ◽  
Yue He ◽  
Xiaodan Zhang
Keyword(s):  
Size Effects ◽  
Coarse Grained ◽  
Ambient Temperatures ◽  
In Situ Techniques ◽  
Transmission Mechanisms ◽  
Deformation Twins ◽  
Ultrafine Grained ◽  
Simulation Results ◽  
Interaction Behaviors

The interactions between dislocations (dislocations and deformation twins) and boundaries (grain boundaries, twin boundaries and phase interfaces) during deformation at ambient temperatures are reviewed with focuses on interaction behaviors, boundary resistances and energies during the interactions, transmission mechanisms, grain size effects and other primary influencing factors. The structure of boundaries, interactions between dislocations and boundaries in coarse-grained, ultrafine-grained and nano-grained metals during deformation at ambient temperatures are summarized, and the advantages and drawbacks of different in-situ techniques are briefly discussed based on experimental and simulation results. The latest studies as well as fundamental concepts are presented with the aim that this paper can serve as a reference in the interactions between dislocations and boundaries during deformation.

Ultrafine Grain Evolution in a Cu-Cr-Zr Alloy during Warm Multidirectional Forging

2014 ◽  
Vol 783-786 ◽  
pp. 2683-2688
Author(s):  
Iaroslava Shakhova ◽  
Andrey Belyakov ◽  
Alexander P. Zhilyaev ◽  
Rustam Kaibyshev
Keyword(s):  
Flow Behavior ◽  
Total Strain ◽  
Ultrafine Grain ◽  
Second Phase ◽  
Steady State Flow ◽  
Multidirectional Forging ◽  
Grain Sizes ◽  
Solution Treated ◽  
Ultrafine Grained ◽  
Zr Alloy

The microstructure evolution and the deformation behavior of a Cu-0.3%Cr-0.5%Zr alloy subjected to multidirectional forging at a temperature of 673 K under a strain rate of about 10-3 s-1 were studied. Following a rapid increase in the flow stress during straining to about 1, the strain hardening gradually decreases, leading to a steady-state flow behavior at total strain above 2. The multidirectional forging led to the development of ultrafine grained microstructures with mean grain sizes of 0.9 μm and 0.64 μm in the solution treated and aged samples, respectively. The presence of second phase precipitates promoted the grain refinement. After processing to a total strain of 4, the fractions of ultrafine grains (D < 2 μm) comprised 0.36 and 0.59 in the solution treated and aged samples, respectively.

Extending Creep and Superplasticity to Materials with Submicrometer Grain Sizes

2007 ◽  
Vol 345-346 ◽  
pp. 539-544
Author(s):  
Megumi Kawasaki ◽  
Cheng Xu ◽  
Z. Horita ◽  
Terence G. Langdon
Keyword(s):  
Plastic Deformation ◽  
Aluminum Alloys ◽  
Severe Plastic Deformation ◽  
Flow Behavior ◽  
Ultrafine Grain ◽  
Grain Sizes ◽  
Large Samples ◽  
Angular Pressing ◽  
Recent Advances ◽  
Ultrafine Grained

The mechanisms of creep and superplasticity occurring in conventional large-grained materials are now understood reasonably well. However, very recent advances in the processing of theoretically-dense metals with submicrometer grain sizes have provided the opportunity to extend the understanding of flow behavior to include materials where the grains are exceptionally small. Using processing through the application of severe plastic deformation, as in procedures such as equal-channel angular pressing, it is now feasible to fabricate relatively large samples having ultrafine grain sizes in the submicrometer or nanometer range. This paper examines these recent advances and gives examples of the flow behavior in ultrafine-grained aluminum alloys.

Novel Formulation Development and Evaluation of Nanoparticles Based in Situ Gelling System for The Ophthalmic Delivery of Ciprofloxacin Hydrochloride

2015 ◽  
Vol 5 (4) ◽  
Author(s):  
Kranti Singh ◽  
Surajpal Verma ◽  
Shyam Prasad ◽  
Indu Bala
Keyword(s):  
Particle Size ◽  
Zeta Potential ◽  
Drug Loading ◽  
In Vitro Release ◽  
Formulation Development ◽  
Ciprofloxacin Hydrochloride ◽  
Potential Value ◽  
The Mean ◽  
In Situ Gelling

Ciprofloxacin hydrochloride loaded Eudragit RS100 nanoparticles were prepared by using w/o/w emulsification (multiple emulsification) solvent evaporation followed by drying of nanoparticles at 50°C. The nanoparticles were further incorporated into the pH-triggered in situ gel forming system which was prepared using Carbopol 940 in combination with HPMC as viscosifying agent. The developed nanoparticles was evaluated for particle size, zeta potential value and loading efficiency; nanoparticle incorporated in situ gelling system was evaluated for pH, clarity, gelling strength, rheological studies, in-vitro release studies and ex-vivo precorneal permeation studies. The nanopaticle showed the mean particle size varying between 263.5nm - 325.9 nm with the mean zeta potential value of -5.91 mV to -8.13 mV and drug loading capacity varied individually between 72.50% to 98.70% w/w. The formulation was clear with no suspended particles, showed good gelling properties. The gelling was quick and remained for longer time period. The developed formulation was therapeutically efficacious, stable and non-irritant. It provided the sustained release of drug over a period of 8-10 hours.

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