Plastic Deformation of Electrodeposited Nanocrystalline Ni-W Alloys at High Temperatures

High-strength nanocrystalline Ni-W alloys containing 16.9 at. % W with average grain size of about 6 nm in diameter has been obtained by electrodeposition. At room temperature, the nominal tensile strength of the alloy was attained to about 1600 MPa, while the plastic strain before fracture was a very low value of 0.05 %. In this case, highly localized shear bands were observed near the fractured surface of the tensile test specimen. When the samples were annealed at 300 °C under a static tensile stress of 327 MPa, the plastic strain was largely increased at the initial period of annealing and then tended to saturate, i.e., 0.54 % for 2 h, respectively. Grain size of the Ni-W alloys was almost saturated to 10 ~ 15 nm after annealing at 300°C for 2 h. It may be expected that the high tensile stress during grain growth might be effective to obtain the large uniform plastic deformation of nanocrystalline Ni-W alloys.

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Plastic deformation technology of high strength deformed magnesium alloy

Thermal Science ◽

10.2298/tsci2106137x ◽

2021 ◽

Vol 25 (6 Part A) ◽

pp. 4137-4143

Author(s):

Lu Xiao ◽

Shutao Xiong

Keyword(s):

Plastic Deformation ◽

Grain Size ◽

Magnesium Alloy ◽

Magnesium Alloys ◽

Slip Surface ◽

High Strength ◽

Slip Direction ◽

Average Grain Size ◽

Cumulative Strain ◽

Simulation Results

The traditional plastic deformation technology of magnesium alloys is relatively poor at high temperature, so a plastic deformation technology of high strength wrought magnesium alloys is designed. Firstly, the slip surface and slip direction which affect the properties of magnesium alloy are analyzed, then the rolling finite element is simulated, the simulation results are visualized, and the simulation information required by the user is output. The results show that the temperature rise decreases with the increase of initial deformation temperature, the average grain size decreases and the uniformity of grain size distribution increases gradually due to dynamic recrystallization, and the cumulative strain and strain distribution in the strain field increases gradually with each pass due to the existence of shear stress in the stress field.

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Structural Transformations and Mechanical Properties of Metastable Austenitic Steel under High Temperature Thermomechanical Treatment

Metals ◽

10.3390/met11040645 ◽

2021 ◽

Vol 11 (4) ◽

pp. 645

Author(s):

Igor Litovchenko ◽

Sergey Akkuzin ◽

Nadezhda Polekhina ◽

Kseniya Almaeva ◽

Evgeny Moskvichev

Keyword(s):

Plastic Deformation ◽

Grain Size ◽

High Temperature ◽

Austenitic Steel ◽

Structural Transformations ◽

Initial State ◽

Twin Boundaries ◽

Metastable Austenitic Steel ◽

Average Grain Size ◽

Heating Up

The effect of high-temperature thermomechanical treatment on the structural transformations and mechanical properties of metastable austenitic steel of the AISI 321 type is investigated. The features of the grain and defect microstructure of steel were studied by scanning electron microscopy with electron back-scatter diffraction (SEM EBSD) and transmission electron microscopy (TEM). It is shown that in the initial state after solution treatment the average grain size is 18 μm. A high (≈50%) fraction of twin boundaries (annealing twins) was found. In the course of hot (with heating up to 1100 °C) plastic deformation by rolling to moderate strain (e = 1.6, where e is true strain) the grain structure undergoes fragmentation, which gives rise to grain refining (the average grain size is 8 μm). Partial recovery and recrystallization also occur. The fraction of low-angle misorientation boundaries increases up to ≈46%, and that of twin boundaries decreases to ≈25%, compared to the initial state. The yield strength after this treatment reaches up to 477 MPa with elongation-to-failure of 26%. The combination of plastic deformation with heating up to 1100 °C (e = 0.8) and subsequent deformation with heating up to 600 °C (e = 0.7) reduces the average grain size to 1.4 μm and forms submicrocrystalline fragments. The fraction of low-angle misorientation boundaries is ≈60%, and that of twin boundaries is ≈3%. The structural states formed after this treatment provide an increase in the strength properties of steel (yield strength reaches up to 677 MPa) with ductility values of 12%. The mechanisms of plastic deformation and strengthening of metastable austenitic steel under the above high-temperature thermomechanical treatments are discussed.

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A Physical-Based Plane Stress Constitutive Model for High Strength AA7075 under Hot Forming Conditions

Metals ◽

10.3390/met11020314 ◽

2021 ◽

Vol 11 (2) ◽

pp. 314

Author(s):

Fulong Chen ◽

Haitao Qu ◽

Wei Wu ◽

Jing-Hua Zheng ◽

Shuguang Qu ◽

...

Keyword(s):

Grain Size ◽

Aluminum Alloy ◽

Plane Stress ◽

Metal Forming ◽

Electron Backscatter Diffraction ◽

High Strength ◽

Material Model ◽

Hot Forming ◽

Industrial Processing ◽

Average Grain Size

Physicallybased constitutive equations are increasingly used for finite element simulations of metal forming processes due to the robust capability of modelling of underlying microstructure evolutions. However, one of thelimitations of current models is the lack of practical validation using real microstructure data due to the difficulties in achieving statistically meaningful data at a sufficiently large microstructure scale. Particularly, dislocation density and grain size governing the hardening in sheet deformation are of vital importance and need to be precisely quantified. In this paper, a set of dislocation mechanics-based plane stress material model is constructed for hot forming aluminum alloy. This material model is applied to high strength 7075 aluminum alloy for the prediction of the flow behaviorsconditioned at 300–400 °C with various strain rates. Additionally, an electron backscatter diffraction (EBSD) technique was applied to examine the average grain size and geometrical necessary dislocation (GND) density evolutions, enabling both macro- and micro- characteristics to be successfully predicted. In addition, to simulate the experienced plane stress states in sheet metal forming, the calibrated model is further extended to a plane stress stateto accuratelypredict the forming limits under hot conditions.The comprehensively calibrated material model could be used for guidinga better selection of industrial processing parameters and designing process windows, taking into account both the formed shape as well as post formed microstructure and, hence, properties.

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Paradox of Strength and Ductility in Metals Processed Bysevere Plastic Deformation

Journal of Materials Research ◽

10.1557/jmr.2002.0002 ◽

2002 ◽

Vol 17 (1) ◽

pp. 5-8 ◽

Cited By ~ 858

Author(s):

R. Z. Valiev ◽

I. V. Alexandrov ◽

Y. T. Zhu ◽

T. C. Lowe

Keyword(s):

Mechanical Properties ◽

Plastic Deformation ◽

Grain Size ◽

Yield Strength ◽

Mechanical Behavior ◽

High Strength ◽

High Ductility ◽

Elongation To Failure ◽

Failure Ductility ◽

Strength And Ductility

It is well known that plastic deformation induced by conventional forming methodssuch as rolling, drawing or extrusion can significantly increase the strength of metalsHowever, this increase is usually accompanied by a loss of ductility. For example, Fig.1 shows that with increasing plastic deformation, the yield strength of Cu and Almonotonically increases while their elongation to failure (ductility) decreases. Thesame trend is also true for other metals and alloys. Here we report an extraordinarycombination of high strength and high ductility produced in metals subject to severeplastic deformation (SPD). We believe that this unusual mechanical behavior is causedby the unique nanostructures generated by SPD processing. The combination ofultrafine grain size and high-density dislocations appears to enable deformation by newmechanisms. This work demonstrates the possibility of tailoring the microstructures ofmetals and alloys by SPD to obtain both high strength and high ductility. Materialswith such desirable mechanical properties are very attractive for advanced structuralapplications.

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Improvement of Strength and Ductility by Combining Static Recrystallization and Unique Heat Treatment in Co-20Cr-15W-10Ni Alloy for Stent Application

Materials Science Forum ◽

10.4028/www.scientific.net/msf.1016.1503 ◽

2021 ◽

Vol 1016 ◽

pp. 1503-1509

Author(s):

Kosuke Ueki ◽

Soh Yanagihara ◽

Kyosuke Ueda ◽

Masaaki Nakai ◽

Takayoshi Nakano ◽

...

Keyword(s):

Heat Treatment ◽

Grain Size ◽

Static Recrystallization ◽

High Strength ◽

Small Variation ◽

Grain Structure ◽

Fine Grain ◽

High Temperature Short Time ◽

Average Grain Size ◽

Strength And Ductility

The Co-20Cr-15W-10Ni (CCWN, mass%) alloy has excellent corrosion resistance and strength-ductility balance and is applied in almost all balloon-expandable stent platforms. To further reduce the invasiveness of stent placement, it is necessary to reduce the diameter of the stent. That is, both high strength and high ductility should be achieved while maintaining a low yield stress. In our previous studies, it was discovered that low-temperature heat-treatment (LTHT) at 873 K improves the elongation of the CCWN alloy. In this study, we focused on the grain refinement by swaging and static recrystallization to improve the strength of the alloy. The as-swaged alloy was recrystallized at 1373–1473 K for 100–300 s, followed by LTHT. A fine grain structure with an average grain size of 3–17 μm was obtained by static recrystallization. The η-phase (M12X-M6X type precipitates, M: metallic elements, X: C and/or N) formed during the recrystallization at 1373–1448 K. The alloys recrystallized at 1448 and 1473 K had a homogeneous structure with a small variation in the grain size. On the other hand, the alloys recrystallized at 1373 and 1423 K had an inhomogeneous structure in which fine and coarse grains were mixed. Both the strength and ductility of the CCWN alloy were improved by combining high-temperature short-time recrystallization and LTHT.

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Microstructural Control of 7075 Al Wrought Alloys through Thixoextrusion Route

Materials Science Forum ◽

10.4028/www.scientific.net/msf.510-511.362 ◽

2006 ◽

Vol 510-511 ◽

pp. 362-365 ◽

Cited By ~ 2

Author(s):

Young Ok Yoon ◽

Hyung Ho Jo ◽

Jin Kyu Lee ◽

Dong In Jang ◽

Shae K. Kim

Keyword(s):

Grain Size ◽

Liquid Fraction ◽

Isothermal Holding ◽

High Strength ◽

Industrial Applications ◽

High Productivity ◽

Die Life ◽

Average Grain Size ◽

Low Energy Consumption ◽

Holding Temperature

Thixoextrusion, one of the thixoforming processes, has advantages of high productivity, reduction of the extrusion pressure, extension of the die life, and cost saving owing to its low energy consumption compared with the conventional extrusion processes. Especially, thixoextrusion process is expected to be very effective for hard-to-form materials with high strength. The present study focuses on 7075 Al wrought alloy to investigate the potential industrial applications of the thixoextrusion process. The microstructural evolution of 7075 Al wrought alloy for thixoextrusion was investigated with respect to isothermal holding temperature and time in the partially remelted semisolid state. The results showed that the liquid fraction increased with increasing isothermal holding temperature and time while the average grain size was inversely proportional to isothermal holding temperature and time up to 5min. However, there was no big change of liquid fraction and average grain size with respect to isothermal holding temperature and time. The important fact that the liquid fraction and average grain size were almost uniform after 5 min holding time is considered very useful for thixoextrusion in terms of process control.

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Study of the Plastic Deformation in Nanocrystalline and Ultrafine Iron and Carbon Steels

Materials Science Forum ◽

10.4028/www.scientific.net/msf.584-586.617 ◽

2008 ◽

Vol 584-586 ◽

pp. 617-622 ◽

Cited By ~ 4

Author(s):

Josep Antonio Benito ◽

Robert Tejedor ◽

Rodriguez Rodríguez-Baracaldo ◽

Jose María Cabrera ◽

Jose Manuel Prado

Keyword(s):

Grain Size ◽

Low Carbon Steel ◽

High Strength ◽

Carbon Steels ◽

Low Carbon ◽

Compression Tests ◽

Consolidation Process ◽

Heat Treated ◽

Average Grain Size ◽

Grain Size Distributions

Samples of nanostructured and ultrafine grained steels with carbon content ranging from 0.05 to 0.55%wt. have been obtained by a warm consolidation process from mechanically milled powders and subsequent heat treatments. In general, homogeneous grain size distributions were obtained except for the low-carbon steel in which a bimodal grain size distribution was observed when it was heat treated at high temperatures. The stress-strain response has been studied by means of compression tests. Nanostructured materials showed high strength but poor results in terms of ductility. In the low-ultrafine range (mean grain size between 100-500 nm) the three materials showed an increase in the ductility with strain softening. Finally, when the average grain size was close to 1 µm samples showed larger ductility and strain hardening.

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Effect of Heat Treatment on Mechanical Properties and Microstructure Morphology of Low-Alloy High-Strength Steel

Archives of Metallurgy and Materials ◽

10.1515/amm-2016-0066 ◽

2016 ◽

Vol 61 (2) ◽

pp. 475-480

Author(s):

K. Bolanowski

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Grain Size ◽

Tensile Strength ◽

Ultimate Tensile Strength ◽

Yield Strength ◽

High Strength Steel ◽

High Strength ◽

Strengthening Phase ◽

Average Grain Size

Abstract The paper analyzes the influence of different heat treatment processes on the mechanical properties of low-alloy high-strength steel denoted by Polish Standard (PN) as 10MnVNb6. One of the findings is that, after aging, the mechanical properties of rolled steel are high: the yield strength may reach > 600 MPa, and the ultimate tensile strength is > 700 MPa. These properties are largely dependent on the grain size and dispersion of the strengthening phase in the ferrite matrix. Aging applied after hot rolling contributes to a considerable rise in the yield strength and ultimate tensile strength. The process of normalization causes a decrease in the average grain size and coalescence (reduction of dispersion) of the strengthening phase. When 10MnVNb6 steel was aged after normalization, there was not a complete recovery in its strength properties.

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Structural Characterization of FeAl28Cr5 Alloy Deformed in the Hot Torsion Process

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.246.43 ◽

2016 ◽

Vol 246 ◽

pp. 43-46 ◽

Cited By ~ 1

Author(s):

Iwona Bednarczyk ◽

Magdalena Jabłońska

Keyword(s):

Plastic Deformation ◽

Grain Size ◽

Structural Changes ◽

Al Alloys ◽

Dynamic Processes ◽

Fine Grained ◽

Average Grain Size ◽

Fine Grained Structure ◽

Hot Torsion

Current research in the field of iron aluminides are directed towards to understand the structural phenomena occurring during plastic deformation of these alloys. The obtained results of the study and collected informations will be used to determine the description of the structural changes taking place during hot deformation of Fe ̶Al alloys. The article presents the results of the study of the alloy FeAl28Cr5 deformed by hot torsion in temperature range of 800÷1100°C and a strain rate of 0.1 s-1. The analysis of the structure of the alloy FeAl28Cr5 allowed to reveal changes caused by dynamic processes of deformation. The results of torsion tests show the possibility to obtain a fine-grained structure with of parameters of the processes (T=1000°C, 1100°C) and strain of ε=40. After deformation at strain of (ε=40) the structure consists of fine grains with a misorientation angle higher than 15°, and the average grain size diameter D=28.5 micrometers. Deformation at a temperature of T=1000°C and 1100°C is accompanied by superplastic flow effect.

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The Correlation Length: A Measure of Inhomogeneities in Polycrystalline Materials

12th International Conference on Nuclear Engineering, Volume 1 ◽

10.1115/icone12-49603 ◽

2004 ◽

Author(s):

Igor Simonovski ◽

Marko Kovacˇ ◽

Leon Cizelj

Keyword(s):

Grain Size ◽

Finite Element ◽

Stress Field ◽

Yield Strength ◽

Correlation Length ◽

Shear Bands ◽

Polycrystalline Materials ◽

Internal Length ◽

Correlation Lengths ◽

Average Grain Size

This paper deals with the correlation length estimated from a mesoscopic model of a polycrystalline material. The correlation length can be used in some macroscopic material models as a material parameter that describes the internal length. It can be estimated directly from the strain and stress fields calculated from a finite-element model, which explicitly accounts for the selected mesoscopic features such as the random orientation, shape and size of the grains. The crystal plasticity material model was applied during the finite-element analysis. Different correlation lengths were obtained depending on whether the strain or the stress field was used. The correlation lengths also changed with the macroscopic load. While the load is below the yield strength the correlation lengths are constant, and of the order of the average grain size. Increasing the load above the yield strength creates shear bands that temporarily increase the values of the correlation lengths calculated from the strain fields. With a further load increase the correlation lengths decrease slightly below the average grain size. The correlation lengths calculated from the stress field are smaller than the ones calculated from the strain field. However, with the exception of the load region where significant shear bands appear, both seem to follow the same qualitative rules.

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