Developing a High Strain Rate Superplastic Forming Capability in Aluminum Alloys PDF Download
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Author:
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Languages : en
Pages : 12
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Book Description
The applications for superplastic forming (SPF) are currently limited because the strain rates involved in the forming process tend to be relatively slow (typically 10(exp -3)-10 (exp -1) 1 s(exp -1). There would be a very significant increase in the applications for SPF if the forming rates were increased to 10(exp -1) 1 s(exp -1). It can be shown on theoretical grounds that SPF-may be achieved at faster rates by reducing the grain size of the superplastic material. Unfortunately, it is generally not possible to achieve grain sizes as small as the submicrometer level using conventional thermo-mechanical processing. This paper demonstrates the potential for achieving ultrafine grain sizes through the application of severe plastic deformation. It is shown that two aluminum- based alloys exhibit superplastic elongations at very rapid strain rates when the alloys are processed using the procedure of Equal-Channel Angular Pressing (ECAP) in which the samples are pressed through a die containing a channel bent into an L-shaped configuration. It is demonstrated also that samples processed by ECAP can be Superplastically formed at very rapid strain rates.
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Category :
Languages : en
Pages : 12
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Book Description
The applications for superplastic forming (SPF) are currently limited because the strain rates involved in the forming process tend to be relatively slow (typically 10(exp -3)-10 (exp -1) 1 s(exp -1). There would be a very significant increase in the applications for SPF if the forming rates were increased to 10(exp -1) 1 s(exp -1). It can be shown on theoretical grounds that SPF-may be achieved at faster rates by reducing the grain size of the superplastic material. Unfortunately, it is generally not possible to achieve grain sizes as small as the submicrometer level using conventional thermo-mechanical processing. This paper demonstrates the potential for achieving ultrafine grain sizes through the application of severe plastic deformation. It is shown that two aluminum- based alloys exhibit superplastic elongations at very rapid strain rates when the alloys are processed using the procedure of Equal-Channel Angular Pressing (ECAP) in which the samples are pressed through a die containing a channel bent into an L-shaped configuration. It is demonstrated also that samples processed by ECAP can be Superplastically formed at very rapid strain rates.
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Category :
Languages : en
Pages : 9
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Book Description
Tests were undertaken to determine the feasibility of producing a superplastic forming capability in a commercial Al-2024 alloy through processing by equal-channel angular pressing (ECAP), where this alloy was selected because it contains no scandium or zirconium additions that are generally beneficial in retaining an array of small grains. Processing by ECAP produced grain sizes in the range from 0.3 to 0.5 micronmeter and static annealing showed these ultrafine grains were reasonably stable at temperatures up to 700 K. Superplastic elongations were achieved after ECAP with a maximum elongation of 500% at 673 K when using a strain rate of 1.0 x l0(exp -2) s(exp-1) The strain rate sensitivity was measured as 0.3 suggesting that dislocation glide is the rate-controlling mechanism. These results demonstrate the potential for achieving high tensile ductilities in conventional commercial aluminum alloys through processing by ECAP.
Author: Amit Kumar Ghosh
Publisher: Minerals, Metals, & Materials Society
ISBN:
Category : Science
Languages : en
Pages : 304
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Book Description
The study of superplasticity and superplastic forming (SPF) has been increasing steadily over the past 15 years. This volume examines the current state of the technology with a focus on technological applications of superplastic forming and the mechanistic behaviour of superplastic materials.
Author: S. Balasivanandha Prabu
Publisher: Elsevier Inc. Chapters
ISBN: 0128068469
Category : Technology & Engineering
Languages : en
Pages : 51
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Book Description
Since the late 1950s, lithium is being used as an alloying element in aluminum. Their excellent ductility, which allows superplastic forming, along with their ability to decrease the density, makes aluminum-lithium alloys a primary choice for many structural applications in aerospace industry. This chapter initially discusses the processes and mechanisms that give rise to significant plasticity/Superplasticity in these alloy systems. The superplastic behavior of Al-Li alloys and their applications in forming are then discussed. The thickness variation during superplastic forming strongly depends on the peak strain rate sensitivity index (m) of the material, and an increase in the m value reduces the thickness variation in the formed component. The factors that help increase the value of m are enumerated. Superplastic forming is carried out at temperatures ≥ 0.5 Tm (Tm is the absolute melting temperature), often closer to 0.7 − 0.8 Tm. Significant cavitation and grain growth are present at such high temperatures. This has ushered in low temperature superplastic forming by the production of ultra-fine grain sizes via dispersion strengthening and severe plastic deformation (SPD). The promise of superplastic forming of Al-Li alloys for the future and the factors including cost that limit the use of Al-Li alloys are also discussed.
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Category :
Languages : en
Pages : 8
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Processing by severe plastic deformation (SPD) leads to very significant grain refinement in metallic alloys. Furthermore, if these ultra fine grains are reasonably stable at elevated temperatures, there is a potential for achieving high tensile ductilities, and superplastic elongations, in alloys that are generally not superplastic. In addition, the production of ultra fine grains leads to the occurrence of superplastic flow at strain rates that are significantly faster than in conventional alloys so that processing by SPD introduces the possibility of using these alloys for the rapid fabrication of complex parts through superplastic forming operations. This paper examines the development of superplasticity in various aluminum alloys processed by equal-channel angular pressing (ECAP).
Author: Suphal P. Agrawal
Publisher:
ISBN:
Category : Technology & Engineering
Languages : en
Pages : 112
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Author:
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ISBN:
Category :
Languages : en
Pages : 158
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Author: Michael Edward McMahon
Publisher:
ISBN: 9781423576730
Category :
Languages : en
Pages : 232
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Book Description
Superplasticity may be defined as the capability of certain polycrystalline materials to deform to extensive plastic elongations prior to failure, often without formation of a neck. Typically, superplasticity refers to tensile elongations greater than 200%, although some elongations have been reported in excess of 5000% Ref 1. While it has been suggested that bronze metals in use in ancient civilizations may have possessed superplastic properties Ref 2, most historical reviews credit the modern-day documentation of superplastic behavior to a paper published in the Journal of the Institute of Metals by G.D. Bengough in 1912 which described extensive elongations in brass Ref 3. Recognition of a stress and strain-rate relationship was first presented qualitatively in a paper by Rosenhain in 1920 which examined a near eutectic Zn- Al-Cu alloy Ref 4. Photomicrographs detailing superplastic grain structures in eutectic Sn-Pb and Bi-Pb alloys deformed to elongations of 2000% were presented in 1934 by Pearson Ref 5. This study was the first to identify an equiaxed grain morphology in the deformed regions and suggest that grain boundary migration may be involved in the deformation processes.
Author: Yuntian Theodore Zhu
Publisher: John Wiley & Sons
ISBN: 1118804481
Category : Technology & Engineering
Languages : en
Pages : 886
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Book Description
Proceedings of a symposium sponsored by the Shaping and Forming Committee of the Materials Processing and Manufacturing Division (MPMD) and the Mechanical Behavior Committee (Jt. SMD/ASM-MSCTS) of the Structural Materials Division (SMD) of TMS (The Minerals, Metals & Materials Society) and held during the 2002 TMS Annual Meeting in Seattle, Washington February 17-21,2002.
Author: Michael E. Kassner
Publisher: Elsevier
ISBN: 0080532144
Category : Technology & Engineering
Languages : en
Pages : 289
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Book Description
* Numerous line drawings with consistent format and units allow easy comparison of the behavior of a very wide range of materials * Transmission electron micrographs provide a direct insight in the basic microstructure of metals deforming at high temperatures * Extensive literature review of over 1000 references provide an excellent reference document, and a very balanced discussionUnderstanding the strength of materials at a range of temperatures is critically important to a huge number of researchers and practitioners from a wide range of fields and industry sectors including metallurgists, industrial designers, aerospace R&D personnel, and structural engineers. The most up-to date and comprehensive book in the field, Fundamentals of Creep in Metals and Alloys discusses the fundamentals of time-dependent plasticity or creep plasticity in metals, alloys and metallic compounds. This is the first book of its kind that provides broad coverage of a range of materials not just a sub-group such as metallic compounds, superalloys or crystals. As such it presents the most balanced view of creep for all materials scientists. The theory of all of these phenomena are extensively reviewed and analysed in view of an extensive bibliography that includes the most recent publications in the field. All sections of the book have undergone extensive peer review and therefore the reader can be sure they have access to the most up-to-date research, fully interrogated, from the world's leading investigators.· Numerous line drawings with consistent format and units allow easy comparison of the behavior of a very wide range of materials· Transmission electron micrographs provide a direct insight in the basic microstructure of metals deforming at high temperatures· Extensive literature review of over 1000 references provide an excellent reference document, and a very balanced discussion
