Showing papers on "Superplasticity published in 2004"
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20 Apr 2004
TL;DR: In this paper, the authors describe the effect of impurities on five-power-law creep behavior in nanoscale and sub-microcrystalline materials and analyze the properties of fine-structured superplastic materials.
Abstract: 1.0 Introduction A. Description of Creep B. Objectives 2.0 Five-Power-Law Creep A. Macroscopic Relationships B. Microstructural Observations C. Rate-Controlling Mechanisms D. Other Effects on Five-Power-Law Creep 3.0 Diffusional Creep 4.0 Harper Dorn Creep A. The Size Effect B. The Effect of Impurities 5.0 Three-Power-Law Viscous Glide Creep 6.0. Superplasticity A. Introduction B. Characteristics of Fine Structure Superplasticity C. Microstructure of Fine Structure Superplastic Materials D. Texture Studies in Superplasticity E. High Strain Rate Superplasticity (HSRS) F. Superplasticity in Nano and Submicrocrystalline Materials 7.0 Recrystallization A. Introduction B. Discontinuous Dynamic Recrystallization (DRX) C. Geometric Dynamic Recrystallization D. Particle Stimulated Nucleation (PSN) E. Continuous Reactions 8.0 Creep Behavior of Particle Strengthened Alloys A. Introduction and Theory B. Small Volume Fraction Particles That Are Coherent and Incoherent with Small Aspect Ratios 9.0 Creep of Intermetallics A. Introduction B. Titanium Aluminides C. Iron Aluminides D. Nickel Aluminides 10.0 Creep Fracture A. Background B. Cavity Nucleation C. Growth
412 citations
TL;DR: The glassy alloy rods exhibit ultra-high fracture strength of 5185 MPa, high Young's modulus of 268 GPa and high specific strength of 6.5B31.
218 citations
TL;DR: In this paper, the structures and properties of nanostructured materials produced by severe plastic deformation (SPD) are reviewed and reported recent progress in determining the deformation mechanisms that lead to these superior mechanical properties.
Abstract: Nanostructured materials produced by severe plastic deformation (SPD) are 100% dense, contamination-free, and sufficiently large for use in real commercial structural applications These materials are found to have high strength, good ductility, superior superplasticity, a low friction coefficient, high wear resistance, enhanced high-cycle fatigue life, and good corrosion resistance This article reviews the structures and properties of nanostructured materials produced by SPD and reports recent progress in determining the deformation mechanisms that lead to these superior mechanical properties
185 citations
TL;DR: In this article, superplastic elongation of 650% was obtained at 530 °C and an initial strain rate of 1.5 s −1 where a maximum strain rate sensitivity of 0.45 was observed.
131 citations
TL;DR: In this paper, the internal friction was used to determine the optimum temperature for superplasticity in ZK60 and AZ91 alloys, and the results showed that internal friction can be practically used to calculate the optimum super-plastic temperature.
110 citations
TL;DR: In this article, it was shown that an Al−5.7%Mg−0.3%Mn alloy subjected to severe plastic deformation through equal-channel angular extrusion exhibits superior superplastic properties in the temperature range of 250-500 °C at strain rates ranging from 1.4×−10−5 to 1.5×−1 s−1 with a maximum elongation-to-failure of 2000% recorded at 450 °C and an initial strain rate of 5.6
101 citations
TL;DR: In this paper, a finite element method was designed to model the mechanisms that cause superplastic deformation, including grain boundary sliding, grain boundary diffusion and surface diffusion, as well as thermally activated dislocation creep within the grains themselves.
Abstract: We describe a finite element method designed to model the mechanisms that cause superplastic deformation. Our computations account for grain boundary sliding, grain boundary diffusion, grain boundary migration, and surface diffusion, as well as thermally activated dislocation creep within the grains themselves. Front tracking and adaptive mesh generation are used to follow changes in the grain structure. The method is used to solve representative boundary value problems to illustrate its capabilities.
95 citations
TL;DR: In this paper, a theoretical model is proposed which describes the generation and evolution of nanoscale cracks at triple junctions of grain boundaries in deformed nanocrystalline materials.
81 citations
TL;DR: In this paper, a field-assisted sintering at temperatures of 1150°−1350°C and a pressure of 66 MPa under vacuum was used to densify nanosized TiN powder, achieving a maximum relative density of ∼97% and a maximum mean grain size of 150−200 nm.
Abstract: Nanosized TiN powder was densified via field-assisted sintering at temperatures of 1150°–1350°C and a pressure of 66 MPa under vacuum. A maximum relative density of ∼97% and a maximum mean grain size of 150–200 nm were obtained. Densification and microstructural evolution have been discussed, in terms of superplasticity and electric-field effects.
80 citations
01 Jan 2004
TL;DR: In this paper, the authors present an approach for doubling the structural efficiency of metallic materials by integrating modeling and computation, which is the main challenge for materials design: integrating modelling and computation.
Abstract: Preface. Introduction. 1: General Overviews. Opportunities and approaches for doubling the structural efficiency of metallic materials D.B. Miracle. The challenge for materials design: integrating modeling and computation C.S. Hartley. The main tendencies in elaboration of materials with high specific strength S. Firstov. 2: Amorphous, Nanocrystalline and Quasicrystalline Materials. Nanostructured materials produced by severe plastic deformation H.P. Stuwe. Development of nanostructured and nanoparticle dispersion-reinforced metallic systems P.R. Subramanian, et al. Nanostructured and nanocomposite light metal-based compounds for hydrogen storage R.A. Varin, et al. Strength and ductility of nanostructured SPD materials R.Z. Valiev. Consolidation of Cu and amorphous Zr-based powders by severe plastic deformation K.T. Hartwig, et al. Structure and properties of carbon-based nanocomposite films G. Radnoczi, et al. Nanocrystallization in iron alloys induced by friction treatment and nitrogen diffusion A. Yurkova, et al. Influence of scandium on amorphization of aluminum alloys A. Slipenyuk, et al. Structure peculiarities of Al63Cu25Fe12 ingots with a quasicrystalline component M. Yefinov, et al. Consolidation of Al-Cu-Fe powders with quasicrystalline component by using high quasihydrostatic pressures O. Bykov, et al. 3: Advanced Aluminum and Magnesium Alloys. High strength aluminum alloys for cryogenic applications O.N. Senkov, et al. Effect of Fe and Si on structure and mechanical properties of complex Al-Zn-Mg-Cu alloys produced by P/M casting techniques Yu. Milman, et al. Study of a zirconium modified 2014 aluminumalloy: analysis of the best warm forming conditions P. Cavaliere. Study of fatigue resistance properties of a zirconium modified 2014 aluminum alloy P. Cavaliere. High strain rate superplastic behavior of Al-Li-Mg-Cu-Sc alloy subjected to severe plastic deformation M.R. Shagiev, et al. Microstructure and mechanical properties od Al-Al4C3 materials M. Besterci, L'. Parilak. Creep behavior and strength of magnesium-based composites V. Sklenicka, et al. 4: Advanced Titanium Alloys and Composites. Multicomponent Ti-Si-based systems M. Bulanova, et al. Effect of Zr on structure and mechanical behavior of Ti-Al-Si alloys I. Gornaya, et al. High-temperature fatigue crack growth resistance of thermo-mechanically and heat treated cast Ti-Si-Al-Zr composites B. Vasyliv, et al. Structure and fracture features of Ti-Si- and Ti-B-based in situ composites O.D. Vasylyev, M.D. Bega. Effect of thermomechanical treatment on structure and properties of titanium-boride eutectic alloys T. Velikanova, et al. New high-strength weldable titanium alloy T110 V.N. Samkov, et al. Features of application of high-strength materials for units of the landing gear of aircrafts 'AN' A.G. Molyar, V.A. Trofimov. 5: Advanced Refractory Alloys. Structures and properties of the refractory silicides Ti5Si3 and TiSi2 and Ti-Si-(Al) eutectic alloys G. Frommeyer, R. Rosenkranz. Refractory metal/silicide multiphase systems for high temperature structural applications M.G. Mendiratta, et al. Microstructural effects and kinetics of high temperature oxidation in Nb-Si base alloys E.S.K. Menon, et al. Development of ductile Cr-Re alloys for high temperature application
76 citations
15 Sep 2004-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the optimal structural superplasticity (defined as the range from the lowest strain rate to the point of inflection on the isostructural, isothermal sigmoidal ln(strain rate)−ln(stress) plot) in both metals and ceramics of grain sizes ranging from a few nanometers to a few micrometers is explained using a model in which rate controlling grain/interphase boundary sliding at the level of atomistics develops by boundary migration (rate controlled by boundary diffusion) to a mesoscopic scale.
Abstract: Optimal structural superplasticity (defined as the range from the lowest strain rate to the point of inflection on the isostructural, isothermal sigmoidal ln(strain rate)–ln(stress) plot) in both metals and ceramics of grain sizes ranging from a few nanometers to a few micrometers is explained using a model in which rate controlling grain/interphase boundary sliding at the level of atomistics develops by boundary migration (rate controlled by boundary diffusion) to a mesoscopic scale (defined to be of the order of a grain diameter or more). Expressions for the threshold stress that should be exceeded for the onset of mesoscopic boundary sliding as a function of grain size and temperature and the steady state strain rate as a function of stress, grain size and temperature have been derived. A conclusion is reached that when the grain size is in the lower nanometer range, grain boundary migration will take place entirely by diffusion. At coarser grain sizes this process will involve a combination of (non-rate controlling) dislocation emission and (rate controlling) boundary diffusion. Experimental support for the above conclusions is demonstrated.
TL;DR: In this paper, a nanocrystalline silicon carbide that was doped with boron and carbon (B,C-SiC) was fabricated using hot isostatic pressing under an ultrahigh pressure of 980 MPa and a temperature of 1600°C.
Abstract: Nanocrystalline silicon carbide that was doped with boron and carbon (B,C-SiC) and contained 1 wt% boron additive and 3.5 wt% free carbon was fabricated using hot isostatic pressing under an ultrahigh pressure of 980 MPa and a temperature of 1600°C. The average grain size of the material was 200 nm. The tensile deformation behavior of this material at elevated temperature was investigated. The nanocrystalline B,C-SiC exhibited superplastic elongation of >140% at a temperature of 1800°C. High-resolution transmission electron microscopy observation and electron energy-loss spectroscopy analysis revealed that this nanocrystalline SiC did not have a secondary glassy phase at the grain boundary and the grain boundary had a strong covalent nature, which means that an intergranular glassy phase was not necessary to obtain superplasticity of covalent materials.
TL;DR: In this paper, a commercial 5083 Al alloy was friction stir processed with three combinations of FSP parameters, and the maximum ductility of 590% was achieved at a strain rate of 3 × 10−3 s−1 and 530 °C in the 6.5-μm grain size FSP material.
Abstract: Friction stir processing (FSP) has been developed as a potential grain refinement technique. In the current study, a commercial 5083 Al alloy was friction stir processed with three combinations of FSP parameters. Fine-grained microstructures with average grain sizes of 3.5–8.5 μm were obtained. Tensile tests revealed that the maximum ductility of 590% was achieved at a strain rate of 3 × 10−3 s−1 and 530 °C in the 6.5-μm grain size FSP material, whereas for the material with 8.5-μm grain size, maximum ductility of 575% was achieved at a strain rate of 3 × 10-4 s−1 and 490 °C. The deformation mechanisms for both the materials were grain boundary sliding (m ~0.5). However, the 3.5-μm grain size material showed maximum ductility of 315% at 10-2 s−1 and 430 °C. The flow mechanism was solute-drag dislocation glide (m ~0.33). This study indicated that establishing a processing window is crucial for obtaining optimized microstructure for optimum superplasticity.
TL;DR: In this paper, a theoretical model is proposed which describes the strengthening and softening mechanisms in nanocrystalline materials under high-strain-rate superplastic deformation.
TL;DR: In this paper, the development of nanocrystalline copper (Nc-Cu) and NiNi and their mechanical properties are discussed. And shortcomings and limitations of various studies that have been conducted are also highlighted.
Abstract: The present review paper traces the development of nanocrystalline copper (Nc-Cu) and nanocrystalline nickel (Nc-Ni) and their mechanical properties. The objective is to summarise the various results available in the literature. The mechanical properties discussed are elastic modulus, Poisson's ratio, hardness, yield stress, ultimate tensile stress, strain/elongation to failure, superplasticity, creep, fatigue and fracture properties. The review is limited to bulk nanocrystalline materials. Shortcomings and limitations of the various studies that have been conducted are also highlighted. The present compilation is expected to be useful for researchers engaged in experimental work and computer modelling in this area.
TL;DR: In this article, the cavitation behavior in heavily extruded fine-grained AZ31 Mg alloys loaded at 200-400 C and 6 · 10 -4 -1 · 10 � 2 s � 1 was analyzed, covering the low temperature or high strain rate superplasticity (LTSP or HSRSP) regimes.
TL;DR: In this paper, the authors demonstrate the possibility to utilize the benefit gained from nano-structure to produce complex shaped ceramic components by superplastic forming and then converting the ductile nano-sized structure into a rigid in situ reinforced microstructure by post annealing above T g.
Abstract: When consolidating nano-sized powders of various oxides and non-oxides susceptible or not susceptible to liquid-phase sintering by SPS technique, we observed a common feature of rapid conversion from nano- to micron-sized structures. The conversion is strongly temperature-dependent and above a critical temperature ( T g ) grain growth occurs very rapidly. Below T g there is a narrow temperature window where nano-sized powders can be fully densified without or with very limited grain growth. Above T g rapid grain growth takes place in fully densified bodies owing to the high driving force provided by the large surface energy of nano-sized grains. This in turn favours the preparation of ceramics with tailored microstructures, e.g. in situ reinforced ceramics. In this presentation, examples will be given to demonstrate the possibility to utilize the benefit gained from nano-structure to produce complex shaped ceramic components by superplastic forming and then converting the ductile nano-sized structure into a rigid in situ reinforced microstructure by post annealing above T g .
TL;DR: In this article, the relative importance of creep and superplastic deformation upon foaming rate, rate of porosity opening and maximum porosity was studied by changing the thermal cycling frequency and maximum temperature.
15 Jan 2004-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the microstructures and properties of powder metallurgy (PM) TiAl alloys fabricated by hot-extrusion of gas-atomized powder at different temperatures (1150, 1250 and 1400) have been investigated.
Abstract: The microstructures and properties of powder metallurgy (PM) TiAl alloys fabricated by hot-extrusion of gas-atomized powder at different temperatures (1150, 1250 and 1400 °C) have been investigated. Microstructure of the alloy fabricated at 1150 °C consists of fine grains of γ and α 2 phases in association with coarse grains of B2 (ordered bcc) phase. Metastable ω particles of ordered hexagonal phase were observed within some B2 grains. This alloy (containing metastable B2 phase) displayed a low-temperature superplastic behavior, i.e. a tensile elongation of 310% was obtained when the alloy was tested at 800 °C under a strain rate of 2×10 −5 s −1 . Microstructure of the alloy fabricated at 1250 °C consists of coarse grains of α 2 phase and fine grains of γ and α 2 phases. This alloy (containing no B2 phase) on the other hand displayed no low-temperature superplasticity, as recorded from the alloy fabricated at 1150 °C. A refined fully lamellar (FL) microstructure was successfully developed within the alloys fabricated at 1400 °C. The widths of γ lamellae are in a range between 100 and 350 nm and the widths of α 2 lamellae are in a range between 10 and 50 nm. Solute effects on the creep resistance of refined FL-TiAl alloy were critically investigated.
01 Jul 2004-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the authors studied the behavior of Pt48.75Pd9.75Cu19.5P22 metallic glass during rapid heating and developed a new microforming system as an application of this phenomenon.
Abstract: In this paper, we studied characteristic behavior of Pt48.75Pd9.75Cu19.5P22 metallic glass during rapid heating. We first rapidly heated a cylindrical specimen of 2 mm in diameter and 5 mm in height by induction heating at a rate of up to 100 K/s. During the heating, glass transition temperature Tg and the crystallization temperature Tx increase with increasing heating rate. The material exhibits a Newtonian viscous flow in the supercooled liquid temperature range, and the normal viscosity decreases with increasing heating rate. The normal viscosity is 2×103 Pa s at a heating rate of 100 K/s. We developed a new microforming system as an application of this phenomenon. The system consists of a rapid resistance-heating unit for foil specimens, a glass transition detector, a linear actuator for driving a tool, and the associated control circuits. With this apparatus, we transferred a three-dimensional micro-shape to the materials within 30 s. A conventional superplastic forging system requires a long time to heat work specimens and to deform them. The developed system thus facilitates mass production of micro parts for micro electro mechanical systems (MEMS).
TL;DR: In this article, the authors describe the application of severe plastic deformation (SPD) processing through the procedure of Equal-Channel Angular Pressing (ECAP) in which a metal is pressed through a die constrained within a channel that is bent through an abrupt angle generally equal to, or very close to, 90°.
TL;DR: In this paper, a superplastic ductility of 1330% was achieved at a temperature of 250 °C and an initial strain rate of 1.4 × 10 −4 s −1 in a ZK60 magnesium alloy processed by sequential procedures of extrusion, compression and rolling.
TL;DR: In this article, the nugget zone of a commercial 7075-T6 aluminum alloy was subjected to friction stir welding (FSW), resulting in the development of a fine-grained structure with an average size of about 3 μm in the Nugget Zone.
Abstract: Commercial 7075-T6 aluminum alloy was subjected to friction stir welding (FSW), resulting in development of a fine-grained structure with average size of about 3 μm in the nugget zone. Static annealing at temperatures ranging from 623 to 773 K for 30 min showed that the fine grain microstructure was stable at temperatures not higher than 723 K. Increase in annealing temperature up to 773 K led to an abnormal grains growth, followed by the development of mm-scale grains. The stamens obtained from the nugget zone demonstrated a superplastic behavior at temperatures ranging from 623 to 723 K and at strain rates ranging from 1 x 10 - 4 to 1 x 10 - 2 s - 1 . Large elongation of about 440% was observed at a temperature of 673 K and at a strain rate of 1 x 10 - 3 s - 1 .
TL;DR: In this article, low-temperature superplasticity and internal friction in microcrystalline ZK60 and AZ91 magnesium alloys processed by equal-channel angular pressing (ECAP) are reported.
TL;DR: In this article, a microstructure-based constitutive model and a multiscale deformation stability criterion that accounts for both geometrical instabilities and microstructural features were used to model and optimize the superplastic blow forming process.
Abstract: Detailed finite element simulations were carried out to model and optimize the superplastic blow forming process using a microstructure-based constitutive model and a multiscale deformation stability criterion that accounts for both geometrical instabilities and microstructural features. Optimum strain rate forming paths were derived from the multiscale stability analysis and used to develop a variable strain rate forming control scheme. It is shown that the proposed optimization approach captures the characteristics of deformation and failure during superplastic forming and is capable of significantly reducing the forming time without compromising the uniformity of deformation. In addition, the effects of grain evolution and cavitation on the superplastic forming process were investigated, and the results clearly highlight the importance of accounting for these features to prevent premature failure.
TL;DR: A review of the recent developments in the mechanics of superplasticity and its applications in industrial practice can be found in this article, where the basic experiments for determining material deformation behavior and related parameters, and constructing super-plastic constitutive equations are reviewed.
TL;DR: In this paper, the influence of SPF conditions on oxidation rates was evaluated in terms of weight gain, α-case depth, and microhardness profile of Ti-6Al-4V (Ti-6-4) sheets.
Abstract: Ti-6Al-4V (Ti-6-4) sheets of two different grain sizes were exposed to time and temperature conditions representative of superplastic forming (SPF). The influence of SPF conditions on oxidation rates was evaluated in terms of weight gain, α-case depth, and microhardness profile. Differences in the response are related to the difference in grain size between the two lots of Ti-6-4. Fine grain Ti-6Al-4V exhibits faster oxygen diffusion in all three areas examined in this study, weight gain, α-case thickness, and increased microhardness depth. The differences were found to be significant relative to diffusion analysis and processing during manufacturing. Results from this work support reduced temperature SPF using fine grain material and the accompanying benefits in manufacturing superplastic parts.
TL;DR: In this article, the superplasticity and diffusion bonding behavior of Zr−10Al−10Ni−15Cu metallic glass indicating amorphous structure was examined on a supercooled liquid region.
TL;DR: In this paper, the deformation of a modified 5154 Al alloy subject to equal channel angular pressing (ECAP) was investigated and it was shown that the deforming of the former was governed by grain boundary sliding but that of the latter was dominated by viscous glide.
TL;DR: In this article, a commercial Al-6 pct Mg-0.3 pct Sc alloy subjected to equal-channel angular extrusion (ECAE) at 325 °C to a total strain of about 16 resulted in an average grain size of about 1 µm.
Abstract: A commercial Al-6 pct Mg-0.3 pct Sc-0.3 pct Mn alloy subjected to equal-channel angular extrusion (ECAE) at 325 °C to a total strain of about 16 resulted in an average grain size of about 1 µm. Superplastic properties and microstructural evolution of the alloy were studied in tension at strain rates ranging from 1.4 × 10−5 to 1.4 s−1 in the temperature interval 250 °C to 500 °C. It was shown that this alloy exhibited superior superplastic properties in the wide temperature range 250 °C to 500 °C at strain rates higher than 10−2 s−1. The highest elongation to failure of 2000 pct was attained at a temperature of 450 °C and an initial strain rate of 5.6 × 10−2 s−1 with the corresponding strain rate sensitivity coefficient of 0.46. An increase in temperature from 250 °C to 500 °C resulted in a shift of the optimal strain rate for superplasticity, at which highest ductility appeared, to higher strain rates. Superior superplastic properties of the commercial Al-Mg-Sc alloy are attributed to high stability of ultrafine grain structure under static annealing and superplastic deformation at T ≤ 450 °C. Two different fracture mechanisms were revealed. At temperatures higher than 300 °C or strain rates less than 10−1 s−1, failure took place in a brittle manner almost without necking, and cavitation played a major role in the failure. In contrast, at low temperatures or high strain rates, fracture occurred in a ductile manner by localized necking. The results suggest that the development of ultrafine-grained structure in the commercial Al-Mg-Sc alloy enables superplastic deformation at high strain rates and low temperatures, making the process of superplastic forming commercially attractive for the fabrication of high-volume components.