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Journal ArticleDOI

Characteristics of superplasticity domain in the processing map for hot working of an Al alloy 2014---20vol.%Al2O3 metal matrix composite

TL;DR: In this paper, a hot working of Al alloy 2014-20vol.% Al2O3 particulate-reinforced cast-plus-extruded composite material has been generated covering the temperature range 300-500 degrees C and the strain rate range 0.001-10 s−1.
Abstract: The processing map for hot working of Al alloy 2014-20vol.%Al2O3 particulate-reinforced cast-plus-extruded composite material has been generated covering the temperature range 300-500 degrees C and the strain rate range 0.001-10 s(-1) based on the dynamic materials model. The efficiency eta of power dissipation given by 2m/(m + 1), where m is the strain rate sensitivity, is plotted as a function of temperature and strain rate to obtain a processing map. A domain of superplasticity has been identified, with a peak efficiency of 62% occurring at 500 degrees C and 0.001 s(-1). The characteristics of this domain have been studied with the help of microstructural evaluation and hot-ductility measurements. Microstructural instability is predicted at higher strain rates above (ls(-1)) and lower temperatures (less than 350 degrees C).
Citations
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Journal ArticleDOI
J.C. Shao1, B.L. Xiao1, Quanchao Wang1, Z.Y. Ma1, Liu Yuwan1, Ke Yang1 
TL;DR: In this article, the authors investigated the constitutive flow behavior and hot workability of powder metallurgy processed 20 vol.%SiC(P)/2024Al composite using hot compression tests.
Abstract: Constitutive flow behavior and hot workability of the powder metallurgy processed 20 vol.%SiC(P)/2024Al composite were investigated using hot compression tests. The modified Arrhenius-type constitutive equations were presented with the values of material constants in consideration as a function of strain. Dynamic material model (DMM) and modified DMM were used to construct the power dissipation efficiency maps, and Ziegler's instability criterion and Gegel's stability criterion were used to build instability maps. The presence of finer SiC(P) and more boundaries resulting from smaller 2024Al powders shifted the dynamic recrystallization domain of the 2024Al matrix to higher strain rate and lower temperature ranges and decreased the peak value of power dissipation efficiency. Large instable regions were found in the form of flow localization and cavitations located at the matrix/SiC(P) interfaces and within the SiC(P) clusters. By comparison, the Gegel's stability criterion was more sensitive to the instability zones than the Ziegler's instability criterion for this material. (c) 2010 Elsevier B.V. All rights reserved.

69 citations

Journal ArticleDOI
TL;DR: In this article, a simple instability condition based on the Ziegler's continuum principles is extended for delineating the regions of unstable metal flow during hot deformation of 2014 Al-20vol% Al2O3 metal matrix composite.

49 citations

Journal ArticleDOI
TL;DR: In this paper, the deformation behavior of a stir cast and hot extruded 14-vol% SiCp/2014Al composite was studied at temperatures from 355 to 495°C and strain rates from 0.001 to 1 s−1, including microstructure evolution and damage formation.

34 citations

Journal ArticleDOI
TL;DR: In this paper, the hot working characteristics of 2124 Al alloy matrix composites reinforced with 0, 5, 10, 15, and 20 vol pct of SiC particulate, produced by the powder metallurgy route, were studied using processing maps.
Abstract: The hot working characteristics of 2124 Al alloy matrix composites reinforced with 0, 5, 10, 15, and 20 vol pct of SiC particulate, produced by the powder metallurgy route, were studied using processing maps. The maps based on the dynamic materials model were generated from the flow stress data obtained from hot compression tests, carried out at strain rates ranging from 0.001 to 10 s−1 and temperatures ranging from 300°C to 525°C. All the compositions studied exhibited domains of dynamic recrystallization (DRX) and superplasticity. Flow instabilities were found at higher strain rates and lower temperatures. The composite with 10 vol pct SiC showed a tendency for abnormal grain growth at lower strains, which manifested itself as a shift in the DRX domain to lower strain rates and the disappearance of the superplasticity domain.

34 citations

Journal ArticleDOI
TL;DR: In this article, the constitutive relationship between stress, strain rate, and temperature was analyzed to obtain a unified description of aluminum alloys produced by powder metallurgy and of aluminum-based metal-matrix composites.
Abstract: The constitutive relationships between stress, strain rate, and temperature were analyzed to obtain a unified description of creep and plasticity of aluminum alloys produced by powder metallurgy and of aluminum-based metal-matrix composites. As both classes of materials are characterized by the existence of a threshold stress (σ 0), a unified description of creep (low strain-rate regime) and plasticity (high strain-rate regime) was obtained by substituting the conventional power-law equation with the sinh relationship, where the applied stress is replaced by the difference between the applied stress and a threshold stress. The stress exponent was n = 3 or 5, and the activation energy was equivalent to the activation energy for self-diffusion or to the activation energy for diffusion of solute elements in the matrix. The model was applied to an unreinforced alloy (2014PM) and a composite (6061 + 20 pct Al2O3) tested in tension (under constant load) or torsion (at constant strain rate) in the temperature range between 300 °C and 500 °C. The results were compared with data available in the literature.

31 citations

References
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Journal ArticleDOI
TL;DR: The constitutive flow behavior of a metal matrix composite (MMC) with 2124 aluminum containing 20 vol pct silicon carbide particulates under hot-working conditions in the temperature range of 300 °C to 550 °C and strain-rate range of 0.001 to 1 s-1 has been studied using hot compression testing.
Abstract: The constitutive flow behavior of a metal matrix composite (MMC) with 2124 aluminum containing 20 vol pct silicon carbide particulates under hot-working conditions in the temperature range of 300 °C to 550 °C and strain-rate range of 0.001 to 1 s-1 has been studied using hot compression testing. Processing maps depicting the variation of the efficiency of power dissipation given by [2m/(m + 1)] (wherem is the strain-rate sensitivity of flow stress) with temperature and strain rate have been established for the MMC as well as for the matrix material. The maps have been interpreted on the basis of the Dynamic Materials Model (DMM). [3] The MMC exhibited a domain of superplasticity in the temperature range of 450 °C to 550 °C and at strain rates less than 0.1 s-1. At 500 °C and 1 s-1 strain rate, the MMC undergoes dynamic recrystallization (DRX), resulting in a reconstitution of microstructure. In comparison with the map for the matrix material, the DRX domain occurred at a strain rate higher by three orders of magnitude. At temperatures lower than 400 °C, the MMC exhibited dynamic recovery, while at 550 °C and 1 s-1, cracking occurred at the prior particle boundaries (representing surfaces of the initial powder particles). The optimum temperature and strain-rate combination for billet conditioning of the MMC is 500 °C and 1 s-1, while secondary metalworking may be done in the super- plasticity domain. The MMC undergoes microstructural instability at temperatures lower than 400 °C and strain rates higher than 0.1 s-1.

35 citations

Journal ArticleDOI
TL;DR: In this article, the hot-working characteristics of the metal-matrix composite (MMC) Al-10 vol % SiC-particulate (SiCp) powder metallurgy compacts in as-sintered and in hot-extruded conditions were studied using hot compression testing.
Abstract: The hot-working characteristics of the metal-matrix composite (MMC) Al-10 vol % SiC-particulate (SiCp) powder metallurgy compacts in as-sintered and in hot-extruded conditions were studied using hot compression testing. On the basis of the stress-strain data as a function of temperature and strain rate, processing maps depicting the variation in the efficiency of power dissipation, given by η = 2m/(m+1), where m is the strain rate sensitivity of flow stress, have been established and are interpreted on the basis of the dynamic materials model. The as-sintered MMC exhibited a domain of dynamic recrystallization (DRX) with a peak efficiency of about 30% at a temperature of about 500°C and a strain rate of 0.01 s−1. At temperatures below 350°C and in the strain rate range 0.001–0.01 s−1 the MMC exhibited dynamic recovery. The as-sintered MMC was extruded at 500°C using a ram speed of 3 mm s−1 and an extrusion ratio of 10∶1. A processing map was established on the extruded product, and this map showed that the DRX domain had shifted to lower temperature (450°C) and higher strain rate (1 s−1). The optimum temperature and strain rate combination for powder metallurgy billet conditioning are 500°C and 0.01 s−1, and the secondary metal-working on the extruded product may be done at a higher strain rate of 1 s−1 and a lower temperature of 425°C.

14 citations

Journal ArticleDOI
TL;DR: In this article, the mixing efficiency of a heavy element is independent of the heat of mixing energy, while that of a light element has a close relation with the heat in mixing, and the experimental results are discussed in terms of cascade mixing and thermal spike mixing.
Abstract: Ion-beam mixing in Al-Pd, Al-Cr, Pd-Cu, Ag-Cu and Ag-Fe bilayers has been studied using Rutherford backscattering spectroscopy (RBS) and Auger electron spectroscopy (AES) over an ion dose range between 1 × 1015 and 1 × 1016 Ar+ cm−2 at room temperature. RBS and AES results show that the mixing efficiency of the light elements is higher than that of the heavy elements. The mixing efficiency of a heavy element is independent of the heat of mixing energy, while that of a light element has a close relation with the heat of mixing. The experimental results are discussed in terms of cascade mixing and thermal spike mixing.

7 citations