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Grain refining of Cu and Ni-Ti shape memory alloys by ECAP process

Greger M., Kocich R., Cizek L.

Journal of Achievements in Materials and Manufacturing Engineering

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2007

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Vol. 20, nr 1-2

247-250

EN

Purpose: This paper was aimed at verification of functionality of the ECAP technology at extrusion of the copper and Ni-Ti alloys. Design/methodology/approach: Cross-section of original samples was 8 x 8 mm and their length was 32 mm. The samples of Cu were extruded at room temperature. For the samples of Ni-Ti alloys was used the two-stage pressing, when the samples were extruded at temperature of approx. T1 = 520 degrees centigrade and T2 = 420 degrees centigrade. In order to increase the concentration of deformation in volume of the sample, the samples were turned around their longitudinal axis by 90 degrees after individual passes and they were extruded again. Analysis of structure was made by using of light microscopy. Findings: deformation forces were measured during extrusion, resistance to deformation was calculated and deformation speed was approximately determined. After individual passes there is occured an accumulation of deformation strengthening (tau3 = 745 Mpa). Research limitations/implications: Microstructure depends on experimental conditions, particularly on number of passes and on rotation of the sample between individual passes. Orginality/value: SPD techniques as ECAP process can be used for non-ferrous metals like Ti, Cu. It was approved that elevated temperature provide a successfully conditions for the fine grained final materials obtaining.

2

Using severe plastic deformation to prepare of ultra fine-grained materials by ECAP method

Rusz S., Malanik K.

Archives of Materials Science and Engineering

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2007

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Vol. 28, nr 11

683-686

EN

Purpose: The purpose of the paper is to design a tool and propose a procedure for verification of development of structure at equal channel angular pressing. The goal is to obtain after extrusion the semi-products of AlCuMg alloys a fine-grain structure which one hand increases strength properties and plasticity, and on the other hand is possible to use it at selected cases for subsequent deformations under conditions of "super-plastic state". Design/methodology/approach: The experiments were aimed the verification of functionality of the proposed equipment, determination of deformation resistance, deformability and change of structure at extrusion of the alloy AlCu4Mg2. Deformation forces were measured at extrusion. The average grain size in cross direction was determined by quantitative metallographic methods. TEM analysis of the structure of AlCu4Mg2 were also made. Findings: The structural analysis of AlCu4Mg2 alloy made by TEM has demonstrated a perfect suitability of the ECAP die design. The process results in a very fine grain structure (100-200 nm) throughout the sample overall volume, at which the starting average grain size was 150 µm. Practical implications: Aluminium alloys of super fine granularity structure are basic intermediate products realised by ECAP technologies. The state of super fine granularity facilitates forming of material in the so-called 'superplastic state'. The achievement of the desired structure depends primarily on the tool geometry, number of passages through the die, magnitude and speed of deformation, process temperature, and lubrication mode. Originality/value: It has been demonstrated that the extrusion technology is suitable for attaining of grain nano-structure in the material investigated in order to determine the number of extrusion cycles needed and the appropriate canal angle with corresponding internal and external bend radii. The obtained results make for success of further investigative efforts in the area.

3

Structural evolution of cooper during by several plastic deformation

Greger M., Kocich R., Čižek L.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2005

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z. 86

127-130

EN

Some experimental results describing microstructural evolution in commercially pure cooper during several plastic deformations by equal channel angular pressing (ECAP) are present. The die angle used in ECAP determines both the shear plane orientation and the strain per pas. It is interesting to study the effect of the separate shear plane orientation and the strain per pass on microstructural development. Authors have experimentally determined development of copper structure and properties at ECAP. Mechanisms of ultrafine grain formation are discussed.