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1

Developing Superplasticity in Ultrafine-Grained Metals

100%

Kawasaki M., Langdon T.

Acta Physica Polonica A

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2015

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vol. 128

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issue 4

470-478

EN

The processing of bulk metals through the application of severe plastic deformation provides an opportunity for achieving exceptional grain refinement with grain sizes typically lying in the submicrometer or even the nanometer range. Provided these small grains are reasonably stable at elevated temperatures, these ultrafine-grained metals will exhibit excellent superplastic properties when pulled in tension at elevated temperatures. Most ultrafine-grained materials have been produced using either equal-channel angular pressing or high-pressure torsion. This paper examines the results for superplasticity reported to date using metallic alloys processed by equal-channel angular pressing and high-pressure torsion, compares the experimental strain rates with those predicted using the theoretical model for conventional superplastic flow and then demonstrates the feasibility of preparing deformation mechanism maps that provide comprehensive information on the flow mechanisms.

2

An Evaluation of Homogeneity and Heterogeneity in Metals Processed by High-Pressure Torsion

81%

Figueiredo R., Kawasaki M., Langdon T.

Acta Physica Polonica A

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2012

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vol. 122

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issue 3

425-429

EN

Processing through the use of high-pressure torsion is attracting much attention at the present time because of the potential for achieving exceptional grain refinement. In principle, it appears that the thin disks used for high-pressure torsion processing should exhibit significant heterogeneity in the as-processed condition. However, experiments show that the development of homogeneity or heterogeneity is dependent upon the crystalline structure of the material. For high-purity aluminum the as-processed microstructure is very homogeneous after five or more revolutions of torsional straining but for the magnesium AZ31 alloy there is a considerable degree of heterogeneity in the as-processed disks.

3

Macroscopic and Microscopic Descriptions of the Plastic Deformation of Fcc Metals over a Wide Range of Strain and Temperature

81%

Csanádi T., Chinh N., Gubicza J., Langdon T.

Acta Physica Polonica A

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2012

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vol. 122

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issue 3

630-633

EN

The plastic behavior of face-centered cubic metals was investigated over a wide range of strain and testing temperature. The experimental stress-strain data were described using both macroscopic and microscopic, well-established relationships. The characteristics of these descriptions are discussed and compared with each other. The analysis of the characteristics leads to a definition of the low and high temperature deformation regions, where the kinetics of both the dislocation-multiplication and the dislocation-annihilation (recovery) are different. For pure aluminum, it is shown that the boundary between these two regions occurs at a homologous temperature of the order of ≈ 0.5 T_{m} where T_{m} is the absolute melting temperature. From this analysis, correlations are also drawn between the macroscopic parameters describing the stress-strain relationship and the fundamental characteristics of the microscopic processes both at room temperature and elevated temperatures.

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3 Acta Physica Polonica A

1 2015

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2 Kawasaki M.

1 Chinh N.

1 Csanádi T.

1 Figueiredo R.

1 Gubicza J.

Developing Superplasticity in Ultrafine-Grained Metals

An Evaluation of Homogeneity and Heterogeneity in Metals Processed by High-Pressure Torsion

Macroscopic and Microscopic Descriptions of the Plastic Deformation of Fcc Metals over a Wide Range of Strain and Temperature