High-Strain Rate Superplasticity in Three Contrasting Fine Grained Aluminum Alloys

AbstractThe superplastic properties and microstructures of three contrasting fine grained aluminium alloys were investigated. These included (i) a powder metallurgy MMC, (ii) a severely deformed spray cast alloy, and (iii) the Zn-22%Al eutectoid alloy. The results showed some differences in the details of behaviour between the alloys. One of these was the presence of true work hardening, associated with dislocation activity, in the MMC, and its absence in the microduplex Zn-Al eutectoid alloy. In addition, the powder route MMC had the high threshold stress (up to 10MPa) commonly encountered in such materials, whereas this was not the case with the cast and severely deformed alloy, indicating that the threshold stress was associated with the presence of ceramic particles in the MMC (oxide + reinforcement). In all the alloys, however, the m value tended to increase with temperature, and this led to a corresponding increase in elongation with temperature until the microstructure became destabilised. In the two predominantly single phase alloys studied this destabilisation corresponded to the solvus temperature. The constantly changing m value indicates that there is no unique value of this parameter. The same was found to be true of the grain size exponent, p. The direct interpretation of apparent activation energies in terms of simple physical processes should be made with care in the light of the present results, as (i) the microstructures of two of the alloys were found to change continuously and significantly with small changes in temperature, and (ii) the fact that m is a function of temperature necessarily implies that the apparent activation energy is a function of stress.

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Development of Superplastic Properties in Quasi Single Phase Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.551-552.357 ◽

2007 ◽

Vol 551-552 ◽

pp. 357-364 ◽

Cited By ~ 8

Author(s):

Roger Grimes ◽

R.J. Dashwood ◽

A. Dorban ◽

M. Jackson ◽

S. Katsas ◽

...

Keyword(s):

Single Phase ◽

Early Stage ◽

Strip Casting ◽

Grain Structure ◽

Freezing Range ◽

Two Phase ◽

Fine Grained ◽

Cast Doubt ◽

Recent Developments ◽

Superplastic Properties

The early view of superplasticity was that it was a phenomenon that could only be exhibited by fine grained, two phase alloys. This effectively ruled out most alloys that possessed attractive service properties. The first material to demonstrate good superplastic properties from a virtually single phase microstructure was the Al-6%Cu-0.5%Zr, AA 2004 but this was followed by superplastic versions of AA7475, AA8090 and AA5083. Superplasticity was also demonstrated in magnesium based alloys at an early stage. More recently different grain control additions, such as scandium or erbium have been investigated and it has also been demonstrated that, in certain circumstances, aluminium simply with the addition of a grain controlling element can exhibit good superplastic behaviour. While conventional wisdom teaches that large fabricating strains are required to confer good superplastic properties in the sheet product, recent results with both aluminium and magnesium alloys cast doubt on this belief. Although, for many years, strip casting has appeared to provide an attractive semi-fabricating route for superplastic sheet problems with centre line segregation in alloys with a wide freezing range have precluded its use. It has been demonstrated that recent developments in strip casting enable production of alloys with as wide a freezing range as AA5182 to be cast with a fine, equiaxed grain structure across the strip thickness. The paper will review the state of these various developments and their implications for the manufacture of superplastic sheet materials.

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Cavitation and failure in a fine-grained Inconel 718 alloy having potential superplastic properties

Materials Science and Engineering A ◽

10.1016/j.msea.2005.08.095 ◽

2005 ◽

Vol 410-411 ◽

pp. 130-133 ◽

Cited By ~ 14

Author(s):

Yi Huang ◽

Terence G. Langdon

Keyword(s):

Inconel 718 ◽

Inconel 718 Alloy ◽

Fine Grained ◽

Superplastic Properties

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Grounded procedures: A proximate mechanism for the psychology of cleansing and other physical actions

Behavioral and Brain Sciences ◽

10.1017/s0140525x20000308 ◽

2020 ◽

pp. 1-78 ◽

Cited By ~ 1

Author(s):

Spike W. S. Lee ◽

Norbert Schwarz

Keyword(s):

Cognitive Processes ◽

Empirical Support ◽

Grounded Cognition ◽

Multiple Perspectives ◽

Physical Processes ◽

Psychological Variables ◽

Sympathetic Magic ◽

Proximate Mechanism ◽

Fine Grained ◽

Level Of Analysis

Abstract Experimental work has revealed causal links between physical cleansing and various psychological variables. Empirically, how robust are they? Theoretically, how do they operate? Major prevailing accounts focus on morality or disgust, capturing a subset of cleansing effects, but cannot easily handle cleansing effects in non-moral, non-disgusting contexts. Building on grounded views on cognitive processes and known properties of mental procedures, we propose grounded procedures of separation as a proximate mechanism underlying cleansing effects. This account differs from prevailing accounts in terms of explanatory kind, interpretive parsimony, and predictive scope. Its unique and falsifiable predictions have received empirical support: Cleansing attenuates or eliminates otherwise observed influences of prior events (1) across domains and (2) across valences. (3) Cleansing manipulations produce stronger effects the more strongly they engage sensorimotor capacities. (4) Reversing the causal arrow, motivation for cleansing is triggered more readily by negative than positive entities. (5) Conceptually similar effects extend to other physical actions of separation. On the flipside, grounded procedures of connection are also observed. Together, separation and connection organize prior findings relevant to multiple perspectives (e.g., conceptual metaphor, sympathetic magic) and open up new questions. Their predictions are more generalizable than the specific mappings in conceptual metaphors, but more fine-grained than the broad assumptions of grounded cognition. This intermediate level of analysis sheds light on the interplay between mental and physical processes.

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Plasma Enhanced Mocvd of BaTiO3 Films

MRS Proceedings ◽

10.1557/proc-243-223 ◽

1991 ◽

Vol 243 ◽

Cited By ~ 3

Author(s):

Peter C. Van Buskirk ◽

Robin Gardiner ◽

Peter S. Kirlin ◽

Salora Krupanidhi ◽

Steven Nutt

Keyword(s):

Single Phase ◽

Chemical Vapor ◽

Dielectric Constants ◽

Polycrystalline Films ◽

Fine Grained ◽

Selected Area Electron Diffraction ◽

Electro Optic ◽

Ir Reflectance ◽

High Dielectric ◽

Very High

AbstractBulk BaTiO3 has a large linear electro-optic coefficient and a very high dielectric constant. We report results obtained for two different MOCVD processes designed to deposit BaTiO3 films with properties suitable for nonlinear electro-optic or high charge storage applications. Epitaxial BaTiO3 films have been grown on NdGaO3 [100] substrates using a high temperature thermal process; the substrate temperature was 1000°C and the total pressure was 4 torr. Selected area electron diffraction (SAED) measurements indicate highly textured, single phase films on the NdGaO3 substrate which are predominantly [100] oriented. Fine grained polycrystalline films have been grown on Pt at 600°C by plasma-enhanced metalorganic chemical vapor deposition (PEMOCVD). Specular IR reflectance was used to determine the concentration of BaCO3 in the film, which was significantly reduced by the plasma. The polycrystalline films had dielectric constants as large as 300 and resistivities exceeding 5 x 108 Ω-cm at room temperature.

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Superplasticity of Friction-Stir Welded Al-Mg-Sc Alloy with Ultrafine-Grained Microstructure Obtained by Warm Severe Plastic Deformation

Materials Science Forum ◽

10.4028/www.scientific.net/msf.879.2395 ◽

2016 ◽

Vol 879 ◽

pp. 2395-2400 ◽

Cited By ~ 1

Author(s):

Sergey Malopheyev ◽

Sergey Mironov ◽

Igor Vysotskiy ◽

Rustam Kaibyshev

Keyword(s):

Large Scale ◽

Base Material ◽

High Strength ◽

Testing Temperature ◽

Total Elongation ◽

Friction Stir ◽

Fine Grained ◽

Angular Pressing ◽

Elongation To Failure ◽

Superplastic Properties

High-strength sheets of Al-5.4Mg-0.2Sc-0.1Zr alloy were produced by equal-channel angular pressing (ECAP) to 12 passes via route BC at 300 °C (573 K) followed by isothermal rolling at 300 °C (573 K) to a total thickness reduction of 80%. The final sheets with ultra-fine grained (UFG) structure were joined by friction stir welding (FSW). The tensile samples including all of the characteristic FSW microstructural zones were machined perpendicular to welding direction. The material demonstrated excellent superplastic properties in the range of temperatures from 350 (623 K) to 450 °C (723 K) at strain rates ranging from 8.3×10-3 s-1 to 3.3×10-1 s-1. The base material was found to be prone to abnormal grain growth at the testing temperature. This led to localization of the superplastic deformation in the stir zone section of the joints and thus limited total elongation-to-failure. The relationship between superplastic ductility and microstructure and application of this technique for the fabrication of large-scale superplastic sheets are discussed.

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Superplastic properties of fine-grained Cu-Zn alloys processed by severe plastic deformation

The Proceedings of Conference of Kyushu Branch ◽

10.1299/jsmekyushu.2002.55.9 ◽

2002 ◽

Vol 2002.55 (0) ◽

pp. 9-10

Author(s):

Terence G. Langdon

Keyword(s):

Plastic Deformation ◽

Severe Plastic Deformation ◽

Fine Grained ◽

Superplastic Properties ◽

Zn Alloys

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Control of Microstructure by MaxStrain Device

Materials Science Forum ◽

10.4028/www.scientific.net/msf.762.55 ◽

2013 ◽

Vol 762 ◽

pp. 55-61

Author(s):

Stan T. Mandziej ◽

Marc Ruggeri

Keyword(s):

Grain Refinement ◽

Single Phase ◽

Precipitation Hardening ◽

Cast Alloy ◽

Strain Rates ◽

Metallic Materials ◽

Plastic Deformations ◽

Ultrafine Grained ◽

Pure Metals ◽

Multi Phase

Grain refinement should increase strength of metallic materials in a predictable manner. However, in applications of severe plastic deformations for this purpose, limits have been observed due to self-recovery and strain-induced precipitation assisted by generation of adiabatic heat. Pure metals and single-phase alloys have not been the best candidates for achieving ultrafine-grained microstructures therefore more often precipitation-hardening multi-phase alloys have been used in SPD experiments. To generate ultrafine-grained microstructures by accumulated multiple compressive strains executed at various strain rates during programmed thermal cycles the MaxStrainTM device was developed for GleebleTM physical simulator. This paper deals with processing of Al-6061 wrought alloy and Al-319 cast alloy by the MaxStrain device, and describes obtained microstructures.

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Effect of upsetting deformation temperature on the formation of the fine-grained cast alloy structure of the Ni–Mn–Ga system

Physics of the Solid State ◽

10.1134/s1063783417080170 ◽

2017 ◽

Vol 59 (8) ◽

pp. 1570-1576 ◽

Cited By ~ 1

Author(s):

I. I. Musabirov ◽

I. M. Safarov ◽

I. Z. Sharipov ◽

M. I. Nagimov ◽

V. V. Koledov ◽

...

Keyword(s):

Deformation Temperature ◽

Cast Alloy ◽

Alloy Structure ◽

Fine Grained

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Monotonic transition based forward body bias for dual threshold voltage low power embedded processors

Advances in Radio Science ◽

10.5194/ars-4-269-2006 ◽

2006 ◽

Vol 4 ◽

pp. 269-273

Author(s):

S. Jayapal ◽

Y. Manoli

Keyword(s):

Threshold Voltage ◽

Leakage Power ◽

High Threshold ◽

Process Technology ◽

Circuit Performance ◽

Fine Grained ◽

Dual Threshold Voltage ◽

And Performance ◽

Forward Body Bias ◽

Body Bias

Abstract. Dual threshold voltage and forward body bias techniques are effective ways to optimally balance the standby leakage power and performance. In this paper, we propose a novel fine-grained forward body biasing scheme for monotonic static logic circuits. In the proposed scheme, the forward body bias is applied to high threshold voltage of either the pull-up or the pull-down network based on the evaluation transition and the state of operation. This technique improves the low skew NAND and NOR circuit performance by 7% and 11%, high skew NAND and NOR by 8% and 13% respectively. It reduces both active and standby leakage power as compared to monotonic static CMOS with dual-VT technique. The simulations are carried out using 130 nm mixed mode process technology to validate our proposed technique.

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