Superplasticity Research Papers - Academia.edu (original) (raw)

Superplastic alloys exhibit extremely high ductility (>300%) without cracks when tensile-strained at temperatures above half of their melting point. Superplasticity, which resembles the flow behavior of honey, is caused by grain boundary sliding in metals. Although several non-ferrous and ferrous superplastic alloys are reported, their practical applications are limited due to high material cost, low strength after forming, high deformation temperature , and complicated fabrication process. Here we introduce a new compositionally lean (Fe-6.6Mn-2.3Al, wt.%) superplastic medium Mn steel that resolves these limitations. The medium Mn steel is characterized by ultrafine grains, low material costs, simple fabrication, i.e., conventional hot and cold rolling, low deformation temperature (ca. 650 °C) and superior ductility above 1300% at 850 °C. We suggest that this ultrafine-grained medium Mn steel may accelerate the commercialization of superplastic ferrous alloys.

- by Dirk Ponge
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- Materials Engineering, Mechanical Engineering, Superplasticity, Interface Design

High-strength (1.2–1.5) C–(2–2.5) Mn–(1.5–2) Si–(0.8–1.5) Cr steels (mass%) consisting of martensite and carbides exhibit excellent superplastic properties (eg strain rate sensitivity m≈ 0.5, elongation≈ 900% at 1023K). A homogeneous martensitic starting microstructure is obtained through thermomechanical processing (austenitization plus 1.2 true strain, followed by quenching). Superplastic forming leads to a duplex structure consisting of ferrite and spherical micro-carbides.

- by Michel Bellet
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- Viscoplasticity, Modeling, Superplasticity, Finite element method

Titanium alloys and titanium matrix composites are useful materials in aerospace applications due to their high strength and stiffness, good corrosion resistance and low density. The gas pressure bulging of metal sheets has become an important forming method. As the bulging process progresses, significant thinning in the sheet material becomes obvious. This paper presents a simple analytical procedure for obtaining the dome height with respect to the forming time useful to the process designer for the selection of initial blank thickness as well as non-uniform thinning in the dome after forming. By thermally cycling through their transformation temperature range, coarse-grained, polymorphic materials can be deformed superplastically, owing to the emergence of transformation mismatch plasticity (or transformation superplasticity) as a deformation mechanism. This mechanism was examined under biaxial stress conditions during thermal cycling of titanium alloys with and without discontinuous reinforcements. For the transformation superplasticity, the strain-rate sensitivity index is considered as unity. The radius of curvature, thickness and height of the dome with respect to the forming time are obtained. The analytical results were found to be reasonably in good agreement with the test results.

- by Chennakesava Reddy A
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- Composites, Superplasticity, Metal Forming
- by Jeoung Han Kim
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- Materials Engineering, Mechanical Engineering, Microstructure, Calcium

Superplastic behavior of fine and ultra fine-grained AA5083 Al alloy was examined using the shear punch test. To achieve fine-and ultra fine-grained microstructures, a relatively new severe plastic deformation (SPD) process, namely Double Equal Channel Lateral Extrusion (DECLE) was employed. The strain rate sensitivity indices (m) of samples were evaluated after 1, 2, 4, and 6 passes for shear strain rates in the range of 3 × 10 −3 to 3 × 10 −1 s −1 and temperatures in the range of 573 to 673 K. For microstructural observations, TEM images together with the corresponding SAED patterns were prepared and utilized. A considerable increase in the m-value was observed after the first pass of the operation for all testing temperatures. The best condition for achieving a good superplasticity for the alloy was found to be a single pass DECLE at 673 K in the strain rate range of 10 − 2 to 10 − 1 s − 1. This process condition resulted in an m-value of 0.43, indicative of a high strain rate superplastic deformation behavior. Further passes of the SPD process did not show any sign of superplasticity until the last pass of the operation, during which the m-value slightly increased, compared with the previous pass.

- by naemeh fakhar
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- Superplasticity
- by Joshua Kuntz
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- Materials Engineering, Mechanical Engineering, Materials Science, Superplasticity
- by Dirk Ponge
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- Materials Engineering, Mechanical Engineering, Superplasticity, Void
- by Jien-wei Yeh
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- Materials Engineering, Mechanical Engineering, Inclusion, Superplasticity
- by Ming-Jen Tan
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- Materials Engineering, Mechanical Engineering, Superplasticity, Strain Rate

Friction Stir processing is among the latest methods which are used to produce the surface composites. Surface composites are used to improve the surface property of the material. Friction Stir process is employed in the grain refinement as well as the processing of various materials by creating surface composites. Friction Stir Processing is an emerging technology which showed significant advancements in recent times. It was developed from the Friction Stir Welding. Since then, various advancements has seen in this process. Various types of elements like aluminum and magnesium can be easily processed by this method. Recently, elements like tungsten has also been reported to be processed by this method. In this study, the existing understanding and the current status of work by Friction stir processing are discussed.

— The reason for choosing this theme is to emphasize the phenomena that occur in a set (measuring device) due to external environmental factors and forces that errors involved in the measurement process. These factors influence the measurement results and their presence can not be seen with the naked eye. Thanks to the progress of last years and helping on software, advanced design, and analysis, the designer have handy ever since the concept of a device able to check the resistance to stresses and deformations that may occur in a structure, model or assembly. Following that verification, it is able to more easily decide how to strengthen the structure needed, more robust modeling benchmarks or the use of harder materials. These issues are highlighted in this paper and illustrated by finite element analysis of the structure of a measuring device using Ansys software.

High temperature plasticity of fine-grained ceramics (ZrO2, Al2O3, etc) is usually associated with a grain boundary sliding process. The aim of the present research is then to improve the high-temperature mechanical strength of polycrystalline zirconia (3Y-TZP) through the insertion of multiwalled carbon nanotubes (CNTs) or silicon carbide whiskers (SiCw), which are susceptible to pin the grain boundaries. The effect of these nano-sized particles on grain boundary sliding has been studied by mechanical spectroscopy.

- by David Dunand
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- Materials Engineering, Mechanical Engineering, Materials Science, Superplasticity

Nitrogen-rich Ca-α-sialon ceramics, prepared with CaH2 as one of the starting powders, were compressively deformed in spark plasma sintering equipment. Compared with the oxygen-rich Ca-α-sialons, increasing onset deformation temperatures (about 150 K higher) were observed for nitrogen-rich Ca-α-sialons deformed at a rate of 2 × 10−3 s−1. High hardness (HV10 = 18–20 GPa) and toughness (KIC = 4–7 MPa m1/2) were maintained after the deformation. Anisotropic grain growth was found to take place during deformation, resulting in anisotropic microstructures, containing coarse and elongated grains. The observed differences in deformation behaviour and properties between nitrogen-rich and oxygen-rich Ca-α-sialons are, as indicated by transmission electron microscopy and electron energy loss spectroscopy analysis, attributed to the presence of reduced amounts of a nitrogen-rich grain-boundary glass phase.

- by Saeid Esmaeilzadeh
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- Materials Engineering, Mechanical Engineering, Microstructure, Superplasticity

Gas pressure bulging of metal sheets has become an important forming method. As the bulging process progresses, significant thinning in the sheet material becomes inevitable. A prior knowledge about non-uniform thinning in the product after forming helps the designer in the selection of initial blank thickness. This paper presents a simple analytical procedure on the thinning of superplastically formed Pb-Sn eutectic alloy spherical domes. It also addresses the issue of instability of deformation.

- by Chennakesava Reddy A
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- Superplasticity, Gas pressure forming
- by Ho-Sung Lee
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- Materials Engineering, Mechanical Engineering, Materials Science, Superplasticity

Abstract Superplastic behavior of fine and ultra fine-grained AA5083 Al alloy was examined using the shear punch test. To achieve fine- and ultra fine-grained microstructures, a relatively new severe plastic deformation (SPD) process, namely Double Equal Channel Lateral Extrusion (DECLE) was employed. The strain rate sensitivity indices (m) of samples were evaluated after 1, 2, 4, and 6 passes for shear strain rates in the range of 3 × 10− 3 to 3 × 10− 1 s− 1 and temperatures in the range of 573 to 673 K. For microstructural observations, TEM images together with the corresponding SAED patterns were prepared and utilized. A considerable increase in the m-value was observed after the first pass of the operation for all testing temperatures. The best condition for achieving a good superplasticity for the alloy was found to be a single pass DECLE at 673 K in the strain rate range of 10− 2 to 10− 1 s− 1. This process condition resulted in an m-value of 0.43, indicative of a high strain rate superplastic deformation behavior. Further passes of the SPD process did not show any sign of superplasticity until the last pass of the operation, during which the m-value slightly increased, compared with the previous pass.

- by naemeh fakhar
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- Materials Engineering, Mechanical Engineering, Materials Science, Superplasticity

In the present work, the influence of c eutectic phase on the cavitation behavior of wrought AZ31 magnesium alloy has been studied through applying a set of low strain rate hot tensile tests. The tensile tests were executed in two temperature range of 300-425°C and 450-500°C; i.e. somewhat below and higher eutectic melting temperature of c precipitates ($437°C). The hot compression characteristics of the experimental alloy were also considered to assist explaining the related deformation mechanisms. The results indicated that a large amount of cavities originates from the c second phases, specially located on grain boundaries. A sharp transition was realized from higher (>3%) to lower cavity area fraction (<0.02%) between 450°C and 500°C. The latter was attributed to the effect of c liquid phase on stress relaxation through accommodating the grain boundary sliding phenomena. In addition, the current work explores the room temperature mechanical properties of tensile deformed specimens using shear punch testing method.

- by Hamid Reza Abedi
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- Superplasticity, Thermomechanical Processing, Cavitation, Magnesium Alloy AZ31
- by Takayoshi Nakano
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- Materials Engineering, Mechanical Engineering, Materials Science, Microstructure

This paper presents the numerical results obtained from the finite element analyses of the superplastic forming (SPF) of AlTi alloys. The models are used to optimise the process and predict forming times in terms of deformed shapes,... more

- by Clayton Adam
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- Materials Engineering, Mechanical Engineering, Superplasticity, Finite Element

The concept of efficiency can be used for comparing the relative performance of various pozzolans when incorporated into concrete. In this paper, an alternative approach for the evaluation of efficiency factor k of a pozzolanic material has been introduced. The method, developed following Abram's strength–W/C ratio rule, calculates efficiency in terms of relative strength and cementitious materials content. The advantage of this method is that only two mixtures are required to determine the k factor of a specific mixture. A laboratory investigation on silica fume (SF) and metakaolin (MK) concrete found that the computed efficiency factors varied with pozzolan type, replacement level and age. At 28 days, the k values ranged from 1.6 to 2.3 for MK and 2.1 to 3.1 for SF mixtures, while at 180 days, the k values varied from 1.8 to 4.0 for MK and 2.4 to 3.3 for SF mixtures. Generally, the k factors increased with age but declined with higher pozzolanic content. It was also observed that change in W/CM ratio from 0.33 to 0.27 did not significantly affect the resultant efficiency factors.

- by Hashim Razak
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- Civil Engineering, Mineralogy, Modeling, Superplasticity
- by Louis Winnubst
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- Materials Engineering, Mechanical Engineering, Materials Science, Microstructure

- by Bing Han
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- Mechanical Engineering, Civil Engineering, Superplasticity, Metal matrix composite
- by James Earthman
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- Materials Engineering, Mechanical Engineering, Materials Science, Superplasticity
- by M. Carsí
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- Engineering, Materials Science, Superplasticity, Creep
- by O. Ruano
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- Materials Engineering, Mechanical Engineering, Microstructure, Superplasticity
- by O. Ruano
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- Superplasticity, Iron, Composite Material, Tensile Stress
- by Nihat Akkus
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- Materials Engineering, Mechanical Engineering, Modeling, Prediction
- by D. Ponge and +1
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- Materials Engineering, Mechanical Engineering, Superplasticity, Interface Design

ABSTRACT An Al 7075 alloy (5.63mass%Zn-2.56mass%Mg-1.68mass%Cu-0.21mass%Fe- 0.19mass%Cr-0.14mass%Si-0.02mass%Ti with balance of Al) was processed by high-pressure torsion (HPT) under an applied pressure of 6 GPa for 1, 3 and 5 revolutions with a rotation speed of 1 rpm at room temperature. Vickers microhardness saturated to a level of 220 Hv after the HPT processing and the grain size was refined to 120 nm at the state of the hardness saturation. Tensile tests were conducted with initial strain rates from 2.0 × 10-4 to 2.0 × 10-2 s-1 at temperatures as 200 °C and 250 °C (equivalent to 0.52Tm and 0.57Tm, respectively, where Tm is the melting point of the alloy). The HPT-processed samples for 3 revolutions exhibited superplastic elongations of 640% and 510% at 250 °C with initial strain rates of 2.0 × 10-3 s-1 and 2.0 × 10-2 s-1, respectively.

- by Seungwon Lee
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- Superplasticity
- by Gaurav Bali
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- Superplasticity, Magnesium, Magnesium Alloys, Superplastic Forming

The microstructural mechanism of grain growth during superplastic deformation is studied in this paper. A new model that considers grain growth is proposed and applied to conventional superplastic materials (Zn-Al alloy, LY12CZ alloy, and 7475 Al alloy). The relationships between the strain, strain rate, test temperature, initial grain size and grain growth in superplastic materials are discussed. The theoretical predictions

- by Ming-Jen Tan
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- Engineering, Materials Science, Microstructure, Modeling

The grain refinement after thermo-mechanical treatment (TMT) was investigated in AZ91, AE42, und QE22 magnesium alloys. The optimal over-aging temperature was determined to be 300 °C in the case of AZ91 and AE42 alloys and 350 °C for QE22 alloy. After optimized TMT, the average grain sizes were 13.5 µm (AE42), 11.1 µm (AZ91) and 1.9 µm (QE22). The QE22 alloy exhibited the superior superplastic properties, with maximum elongation to failure 750 % and strain rate sensitivity parameter m=0.73. The Friction Stir Welding showed that the original base material grain structure of the alloys AZ31 and AZ91 replaced by ultrafine grains in the stir zone. The purpose of the present paper is to present the results of the grain refinement in magnesium alloys by thermo mechanical treatment and stir welding.

- by Robert Král
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- Materials Science, Metallurgy, Superplasticity, Friction Stir Welding

Using a model that gives a realistic description of the plastic flow of polycrystals with refined grain size resulted in discrepancies being found in the postulates of the mathematical theory of plasticity. The new proposed time-dependent... more

- by Victor Conte Pozo
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- Materials Engineering, Mechanical Engineering, Superplasticity, Creep

In this study, a novel method of friction stir forming (FSF) was conducted for mechanical interlocking of Zn-22Al superplastic alloy and thin copper wire insulated by polyimide. The potential development of a composite material capable of transmitting electrical energy or electric signals was studied experimentally, and it was concluded that FSF can successfully interlock insulated copper wire with Zn-22Al superplastic alloy. The authors suggest the possibility that FSF could join sheets of Zn-22Al alloy by pressure welding and superplastic forming and diffusion bonding (SPF/DB). Trials of FSF were carried out on a modified vertical milling machine. The results are discussed in terms of microstructure observations, hardness distributions, and temperature measurements.

- by Hamed Mofidi Tabatabaei
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- Engineering, Materials Science, Metallurgy, Superplasticity

Fine grained, three-phase ceramic composites that exhibit favorable toughness, hardness, and high room-temperature strength were evaluated for high-temperature mechanical stability. A 50vol%Al2O3–25vol%NiAl2O4–25vol%3 mol%yttria-stabilized tetragonal zirconia polycrystal (3Y–TZP) and a 33vol%Al2O3–33vol%NiAl2O4–33vol%3Y-TZP composite were compression creep tested at temperatures between 1350 and 1450 °C under constant stresses of 20–45 MPa. The three-phase microstructure effectively limited grain growth (average d0 = 1.3 μm, average df = 1.6 μm after 65% true strain). True strain rates were 10−4 to 10−6 s−1 with stress exponents n = 1.7 to 1.8 and a grain-size exponent p = 1.3. A method for compensating for grain growth is presented using stress jump tests. The apparent activation energy for high-temperature deformation for 50vol%Al2O3–25vol%NiAl2O4–25vol%3Y–TZP was found to be 373 kJ/mol-K.

It was reported that superplastic boronizing process (SPB) provides a much faster boronizing rate than the conventional boronizing process (CB). This process was conducted on duplex stainless steel (DSS) which exhibit superplasticity. The study concentrated on the effect of strain rate and compression strain on SPB. The process was conducted under four different strain rates and three diferent strains condition. Boronizing was successfully conducted with the best result obtained under the high strain rate range of 5 x 10-5 s-1 to 1 x 10-3 s-1 which is associated with the superplastic region. Through SPB, movement of atoms into the specimen was highly accelerated by the grain boundary sliding process leading to a formation of thick and hard boronized layer in extraordinarily short period of time.

- by Hanis Ayuni Mohd Yusof
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- Superplasticity, Strain Rate, Surface Properties, Duplex Stainless Steel
- by I-wei Chen
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- Materials Engineering, Mechanical Engineering, Materials Science, Microstructure

Multi-level modeling adaptive to theoretical treatise of superplastic deformation is proposed not only to make process simulation for superplastic forming but also to describe the microstructural change taking place in materials processing. Use of the unit cell modeling enables us to make theoretical linkage between the macroscopic and the mesoscopic models. The fundamental theory is introduced with some comments on the unit cell model for macro-micro mechanics linkage and the advanced granular modeling for mesoscopic representation of superplasticicty. The sinter-forging process is employed for practical demonstration of the present multi-level modeling.

- by Tatsuhiko Aizawa
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- Superplasticity, Finite element method, Homogenization, Forging

Intrinsic difficulty of metal forming in magnesium alloys must be overcome by new processing. Superplatic injection forming is one of the most promising methodologies. Stroke velocity controlled forming system was developed to evaluate the formability of AZ91 at 573 K both in upsetting and backward-extrusion modes. Uniaxial constitutive equation was used together with consideration of grain growth to predict the stress-strain rate and the stress-stroke relations in upsetting experiments. Double flange, thin-walled cup can be superplastically formed from a cylindrical billet.

- by Tatsuhiko Aizawa
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- Materials Science, Superplasticity, Strain Rate, Grain Growth

The instability and the localization process of unstable plastic flow during constant pressure bulging of superplastic Ti6Al4V sheets at 900°C are analyzed. A generalized stability criterion is developed by generalizing Hart's... more

- by Li Chung
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- Materials Engineering, Mechanical Engineering, Materials Science, Superplasticity
- by David Dunand
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- Materials Engineering, Mechanical Engineering, Materials Science, Plasticity
- by David Dunand
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- Materials Engineering, Mechanical Engineering, Materials Science, Superplasticity