SUPERPLASTIC BEHAVIOR OF COARSE-GRAINED Al-Mg ALLOY

2012 ◽  
Vol 06 ◽  
pp. 401-406 ◽  
Author(s):  
HAOYAN DIAO ◽  
REHAN QAYYUME ◽  
TINGTING WANG ◽  
SHASHA ZHAO ◽  
CHAOLI MA
Keyword(s):  
Strain Rate ◽  
Constant Strain Rate ◽  
Rate Sensitivity ◽  
Superplastic Forming ◽  
Mg Alloy ◽  
Coarse Grained ◽  
Sensitivity Index ◽  
Maximum Elongation ◽  
Dislocation Glide ◽  
Elongation To Failure

This paper concentrates on the study of the superplastic response of coarse-grained Al - Mg alloys under uniaxial tension at different temperatures (ranging from 400°C to 525°C) and strain rates (10-2 S-1, 10-3 S-1 & 10-4 S-1). The microstructures have been analyzed using optical (OM) and transmission electron microscopy (TEM). It has been observed that continuous re-crystallization occurs during hot deformation of the alloy at the temperature of 425°C and strain rate of 10-2S-1. At the temperature of 425°C and strain rate of 3.78×10-3S-1, this Al - Mg alloy has the maximum elongation to failure of 181%, which is sufficient for manufacturing of extremely complex shapes using superplastic forming technology. The constant strain rate sensitivity index m and TEM observations show that in this case deformation mechanism involved is dislocation glide. Recrystallization during the hot tension greatly enhanced the plasticity of the coarse-grained material at a strain rate of about 10-2S-1 and the maximum elongation changes as a function of the strain rate.

Grain Refinement during Superplastic Deformation of Coarse-Grained Al-Mg-Cu Alloys

2006 ◽  
Vol 509 ◽  
pp. 75-80 ◽  
Author(s):  
M.I. Cruz-Palacios ◽  
D. Hernández-Silva ◽  
L.A. Barrales-Mora ◽  
M.A. García-Bernal
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Grain Refinement ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Mg Alloy ◽  
Coarse Grained ◽  
Dislocation Creep ◽  
Rolled Plate ◽  
Strain Rates

In the present study the superplastic behavior of Al-6%Mg–0.5%Cu and Al–8%Mg– 0.5%Cu in a coarse grain size condition has been studied. The alloys are melted in an electrical furnace under argon atmosphere. The ingots (25 mm thick) are homogenized at 400 °C during 72 h and then rolled at 430 °C to a thickness of 5 mm. The mean grain size after rolling is 55 µm for the 6%Mg alloy and 61 µm for the 8%Mg alloy. Tensile test specimens are machined from the rolled plate in the rolling direction. Strain-rate-change tests at temperatures between 300 and 450 °C and strain rates between 1x10-4 and 1x10-1 s-1 are carried out to determine the strain rate sensitivity of the flow stress. Finally, elongation to failure tests are conducted at temperatures and strain rates where the alloys show a high strain rate sensitivity. Elongations higher than 390 % are obtained for the 8%Mg alloy. It is observed that the grip regions of the deformed samples show coarser grains than the regions near to the fracture surface. This means that grain refinement takes place during deformation, suggesting that the principal deformation mechanism is dislocation creep.

Theoretical Deduction of Constitutive Equations with Variational Parameters during Superplastic Tension

2014 ◽  
Vol 941-944 ◽  
pp. 1509-1512
Author(s):  
Zhi Ping Guan ◽  
Xiao Fang Guan ◽  
Yu Quan Song
Keyword(s):  
Strain Rate ◽  
Test Data ◽  
Constitutive Equations ◽  
Constant Strain Rate ◽  
Rate Sensitivity ◽  
State Equation ◽  
Sensitivity Index ◽  
Tensile Tester ◽  
Strain Rate Sensitivity Index ◽  
Superplastic Tension

In this article, firstly, the strain hardening index and the strain rate sensitivity index were deducted from the general state equation and the mechanical meaning of the two indexes were correspondingly depicted, and then constitutive equations, where both/either of the two indexes appear as constants, were theoretically deducted from the same state equation. Secondly, constitutive equations where both/either of the two indexes present as variables were put forward by numerical simulation. Next, constitutive equations were built, where mechanical variables are replaced by test data obtained on an electronic universal tensile tester with the capacity to carry out a true constant strain rate path. Finally, based on the test data of Zn-5%Al during superplastic tension, it is proved that the theoretical results in this article are valid.

Determination of Superplastic Material Properties for Parent Material and Friction Stir Welded Joint of Al-Alloy AA6061-T6

2015 ◽  
Author(s):  
Senthil Kumar Velukkudi Santhanam ◽  
Ganesh Pasupathy ◽  
Padmanabhan Kuppuswamy Anantha
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Material Properties ◽  
Rate Sensitivity ◽  
Superplastic Forming ◽  
Parent Material ◽  
Sensitivity Index ◽  
Superplastic Material ◽  
Friction Stir ◽  
Strain Rate Sensitivity Index

Superplastic forming (SPF) takes the advantage of the metallurgical phenomenon of superplasticity (SP) to form complex and highly intricate bulk and sheet metal parts. SP refers to the extraordinary formability of certain metals and alloys, ceramics, composites (both metallic- and ceramic-based), dispersion strengthened materials, nanostructured materials and bulk metallic glasses, which allows them to suffer elongations of several hundred percent under the action of tensile forces. The superplastic forming characteristics of materials like aluminium, titanium and magnesium alloys have been clearly identified in order to produce complicated near-net shapes. These materials are used in the aeronautical manufacturing industry and automotive manufacturing industries due to the significant weight (by ∼ 30%) and cost (by ∼ 50%) saving that is possible. Some research work has proved superplastic forming of friction stir welded (FSW) joints also. The FSW joint efficiencies have been characterized by mechanical and metallurgical examination. Studies are also available on the behavior of FSW joints of similar and dissimilar metals. Information on the performance of friction stir welded joints during superplastic forming is rather limited, but it is important to achieve excellent properties in the friction stir welded joints also during superplastic forming. FSP (friction stir processing) – SPF (superplastic forming) is presently being promoted as a very viable near-net shape technology for making very large and complicated sheet metal products. To achieve this superplastic material parameters are much required in industry to develop new shapes. One has to understand the flow rule relationship and mechanics involved during sheet metal forming at high temperature to select the material and forming tool with selected process parameters. This paper deals with the determination of superplastic material properties of non-superplastic aluminum alloy AA6061-T6. The superplastic material properties like strain rate sensitivity index, flow stress and strain rate were determined for both the selected material and friction stir welded sheets at various tool rotation speeds. The superplastic free blow forming experiments were performed for various constant temperatures and pressure for the parent material. Similarly the superplastic free blow forming experiments were performed for the friction stir welded joint for various tool rotation speed at constant temperature. The methods were used to determine the material properties are straight line fit method and polynomial regression method. The superplastic forming height is significantly high in case of the FSW specimens at 2000 rpm, the initial forming rate is faster and the strain rate sensitivity index obtained is also higher when compared to the parent material properties. The strain rate sensitivity index obtained for friction stir welded specimen during superplastic forming was foundto have improved when compared to the parent material.

The Role of Microstructural Aspects on the Performance of Coarse-Grained Superplastic Al Alloys

2005 ◽  
Vol 495-497 ◽  
pp. 883-888 ◽  
Author(s):  
A.R. Chezan ◽  
Jeff T.M. de Hosson
Keyword(s):  
Grain Size ◽  
Aluminum Alloys ◽  
Strain Rate ◽  
Tensile Elongation ◽  
Rate Sensitivity ◽  
Solute Drag ◽  
Coarse Grained ◽  
Sensitivity Index ◽  
Premature Failure ◽  
Principal Mechanism

Deformed under optimum conditions of temperature and strain rate, coarse-grained aluminum alloys show elongation to failure in excess of 300%. The strain rate sensitivity index and the activation energy point to solute drag creep as the principal mechanism, a mechanism that has virtually no grain size dependence. The present study summarizes microstructural effects that are grain size dependent and which can influence the values of the maximum tensile elongation that can be obtained in coarse-grained aluminum alloys. Such effects like inhomogeneous refinement of the microstructure accompanied by the increase of the ratio of low/high angle grain boundaries and that of the texture contributes to flow stress instabilities leading to necking and premature failure.

The Background to Superplastic Forming and Opportunities Arising from New Developments

2020 ◽  
Vol 306 ◽  
pp. 1-8
Author(s):  
Terence G. Langdon
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
High Strain ◽  
Rate Sensitivity ◽  
Superplastic Forming ◽  
Industrial Applications ◽  
Superplastic Flow ◽  
Dislocation Glide ◽  
Wide Range ◽  
Historical Developments

The occurrence of superplastic flow in metals has a long history but it is only over the last three or four decades that it was recognized that this process provides an opportunity for fabricating complex parts, especially curved panels, that may be used in a wide range of industrial applications. In practice, this use is dependent upon the high strain rate sensitivity of ~0.5 which is an inherent feature of true superplastic flow but in practice excellent forming may be achieved also through the use of metals deforming within the range of dislocation glide where the strain rate sensitivity is close to 0.3. New possibilities have arisen over the last two decades with the demonstrations that exceptionally refined microstructures, usually within the submicrometer or even the nanometer range, may be prepared from a wide range of commercial alloys through the application of severe plastic deformation in which the material is subjected to a very high strain without any significant changes in the overall dimensions of the sample. This presentation examines these historical developments and describes the new processing procedures that provide new opportunities within the field of superplastic forming.

Superplasticity of Al-Mg-Zr Alloy

2018 ◽  
Vol 385 ◽  
pp. 114-119 ◽  
Author(s):  
Andrey Mochugovskiy ◽  
Anastasia V. Mikhaylovskaya ◽  
Walubita Mufalo ◽  
Vladimir K. Portnoy
Keyword(s):  
Elevated Temperature ◽  
Strain Rate ◽  
Metastable Phase ◽  
Constant Strain Rate ◽  
Tensile Tests ◽  
High Density ◽  
Maximum Elongation ◽  
Tem Analysis ◽  
Elongation To Failure ◽  
Zr Alloy

The microstructure and superplasticity of the thermomechanically proceeded sheets of Al - 3wt.%Mg - 0.25wt.%Zr were investigated. High density of L12-structured fine dispersoids of Al3Zr metastable phase was observed by TEM analysis. Alloy demonstrated high recrystallization resistance at elevated temperature due to Al3Zr dispersoids. The tensile tests were carried out in a temperature range of 440-500 °C and a strain rate of 1×10-3to 1×10-2s-1. The maximum elongation to failure of 370% was observed at 480 °C at the constant strain rate values of 2×10-3and 5×10-3s-1.

Low-Temperature Superplasticity in an Al-Mg-Sc Alloy Processed by ECAP

2016 ◽  
Vol 838-839 ◽  
pp. 422-427 ◽  
Author(s):  
Diana Yuzbekova ◽  
Anna Mogucheva ◽  
Rustam Kaibyshev
Keyword(s):  
Strain Rate ◽  
Rate Sensitivity ◽  
Sensitivity Coefficient ◽  
Strain Rates ◽  
Maximum Elongation ◽  
Superplastic Behavior ◽  
Angular Pressing ◽  
Ultrafine Grained ◽  
Elongation To Failure ◽  
Average Size

The ultrafine grained structure of an AA5024 with an average size of ∼0.7 μm was produced by equal-channel angular pressing (ECAP) at 300°C with a total strain of ~12. Superplastic behavior of this alloy was examined in the temperature interval 175 - 300°C at strain rates ranging from 10-4 to 10-1 s-1. The maximum elongation-to-failure of ~1200% with the corresponding strain rate sensitivity coefficient, m, of ∼0.49 was attained at a temperature of 275°C and a strain rate of 5.6×10–3s–1. At 175°C (~0.53Tm, where Tm is the melting point), the elongation-to-failure of ~370% with the m value of ~0.3 was found at ε̇=1.4×10–4 s–1.

Mechanical behaviour and superplastic forming capabilities of extra-low interstitial grade Ti-6Al-4V wire alloy with numerical verification

2007 ◽  
Vol 221 (3) ◽  
pp. 165-174 ◽  
Author(s):  
M D Naughton ◽  
P Tiernan
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Superplastic Forming ◽  
Effect Of Temperature ◽  
Sensitivity Index ◽  
Numerical Verification ◽  
Strain Rates ◽  
Strain Rate Sensitivity Index

In this paper, the behaviour of extra-low interstitial (ELI) grade Ti-6Al-4V wire alloy has been extensively studied at varying strain rates in the range of 10-5-102 s-1 at temperatures ranging between 750 °C and 1050 °C using processing maps and experimental data to determine the material's mechanical and superplastic forming capabilities. From the slope of a log plot of strain rate versus flow stress, the strain-rate sensitivity index, m, was determined. A plot of m versus the log of strain rate was produced in order to identify the key strain rates in which ELI grade Ti-6Al-4V exhibits its superplastic regime. It was determined that this alloy is most sensitive to superplastic forming within a narrow strain-rate band of 10-4-10-3 s-1 and has a maximum strain-rate sensitivity index, m = 0.45. At strain rates below and above this range, the material exhibited negligible levels of superplasticity. The key temperature for superplastic forming was determined to be 950 °C. The effect of temperature on flow stress and flow stability was analysed using the Zener-Holloman parameter. The experimentally determined results showed excellent agreement with Guo and Ridley's activation mathematical model.

scholarly journals Dislocation-Controlled Low-Temperature Superplastic Deformation of Ti-6Al-4V Alloy

2021 ◽  
Vol 7 ◽  
Author(s):  
Chao Liu ◽  
Xin Wang ◽  
Ge Zhou ◽  
Feng Li ◽  
Siqian Zhang ◽  
...  
Keyword(s):  
Low Temperature ◽  
Strain Rate ◽  
Deformation Mechanism ◽  
Superplastic Deformation ◽  
Rate Sensitivity ◽  
Stress Index ◽  
Sensitivity Index ◽  
Dislocation Glide ◽  
Superplastic Properties ◽  
Superplastic Tension

The superplastic tension and deformation mechanism of Ti-6Al-4V alloy at 923 K and a tensile speed of 10−3, 5 × 10−3, or 5 × 10−2 s−1 was studied on an AG 250KNE electronic tension tester. Through theoretical modeling, the unit dislocation count of this alloy during superplastic deformation was introduced into the Ruano–Wadsworth–Sherby (R-W-S) deformation mechanism map, and a new deformation mechanism map involving dislocation count was plotted. Thereby, the mechanism underling the low-temperature superplastic deformation of this alloy was predicted. It was found the superplastic tension of Ti-6Al-4V at the tested temperature was controlled by dislocation movement, and with an increase in strain rate, the deformation transited from the dislocation-controlled mechanism with a stress index of 4 to the dislocation glide mechanism with a stress index of 5 or 7. At the strain rate of 10−3 s−1, this alloy reached the largest tension rate of 790% and strain rate sensitivity index of 0.52 and had excellent low-temperature superplastic properties.

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