Wyniki wyszukiwania - Biblioteka Nauki

1

Forging and rolling of magnesium alloy AZ61

100%

Greger M. , Kocich R. , Čižek L.

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tom Vol. 20, nr 1-2

447-450

EN

Purpose: The paper summarises results of experiments aimed at development of structure of modified alloy AZ61 at hot deformation. Design/methodology/approach: Deformation behaviour of alloy was verified at the temperature of 420 degrees centigrade by rolling at 380 degrees centigrade by forging, respectively. Findings: Magnesium alloy AZ 61 have hexagonal structure and their forming is at room temperatures very difficult, that's why big plastic deformations are carried out in hot condition. After plastic deformations was obtained that original grain size decreased 15 times. Research limitations/implications: This paper provide data about magnitude of deformation, strain rate and temperature of forming at different techniques of plastic deformation. It was aimed to determine the conditions for non problem rolling and forging respectively. Practical implications: Initial structure was as cast and after heat treatment T4. Heat treatment appeared much better for forming as well as forging than rolling because of state of stress. Originality/value: Role of beta phase (Mg17Al12) in these alloys at plastic forming is very important, such that how it was obtained, best final properties of AZ 61 alloy supports very fine particles, distributed into Mg matrix. Next a relevant information is that multi stage forming process is much better in comparison with a big single reduction.

2

Drawing of tungsten wire at elevated temperatures

100%

Greger M. , Muskalski Z. , Kocich R. , Kuretova B.

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tom Vol. 74, nr 1-2

17-20

EN

The paper describes deformation behaviour, mechanical properties and structure of cold drawn tungsten wires and heat treated by annealing at various temperatures. Introductory part describes technological process and analysis of drawing technology. Dependence of change of mechanical properties of tungsten wires with various chemical composition on structural states caused by deformation strengthening and annealing was investigated experimentally.

PL

W pracy opisano przebieg deformacji, własności mechaniczne i strukturalne ciągnionych na zimno drutów wolframowych oraz obróbkę cieplną przez wyżarzanie w różnych temperaturach. Przedstawiono części opisu procesu technologicznego i analizę technologii ciągnienia. Przeprowadzono badania doświadczalne zależności zmian własności mechanicznych drutów wolframowych o różnym składzie chemicznym, zmian strukturalnych wywołanych przez umocnienie odkształceniowe oraz wyżarzanie.

3

Possibilities of mechanical properties and microstructure improvement of magnesium alloys

88%

Greger M. , Kocich R. , Čížek L. , Dobrzański L. A. , Juřička I.

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2007

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tom Vol. 28, nr 2

83-90

EN

Purpose: Magnesium alloys are the very progressive materials whereon is due to improve their end-use properties, which. Especially, wrought Mg alloys attract attention since they have more advantageous mechanical properties than cast Mg alloys. Design/methodology/approach: The presented article shows some specific physical-metallurgical characteristics of magnesium alloys of the AZ91 kind after hot forming. Special attention has been focused on the analysis of mutual relations existing between the deformation conditions, microstructural parameters, and the achieved mechanical properties. Findings: The discussed topic includes namely the monitoring of the structures in the initial cast state and after the heat treatment of the T4 kind and the influence of rolling in hot state at different temperatures on this structure. The results of torsion tests of AZ91, AZ61 and AZ31 were added. Research limitations/implications: The results of this paper evinces that a combination of ECAP technology with conventional rolling is very effective tool for improve a final properties of magnesium alloys in practical use. Practical implications: It would be appropriate a extrusions processes for increasing of mechanical properties on their treatment by plastic deformations in a rolling mills. Originality/value: It is explained a big consequence of the ECAP integration between classical forming techniques.

4

Structure and properties of alloys of the Mg-Al-Zn system

75%

Cizek L. , Greger M. , Dobrzański L. A. , Juricka I. , Kocich R. , Pawlica L. , Tański T.

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tom Vol. 32, nr 2

179-187

EN

Purpose: In the following paper there have been the structure and complex of mechanical properties of magnesium alloys presented which requires very often knowledge of elastic-plastic properties at elevated temperatures. These properties are connected with microstructure that is influenced by metallurgical and technological factors and conditions of exploitation. The influence of used method ECAP for superplasticity will be investigated. Design/methodology/approach: The tensile test in dependence on temperature of magnesium alloys was based on investigation of mechanical properties. The following results concern light and scanning microscopy for metallographic and fracture analyses of alloys after testing were used. Findings: Objective of this work consisted in determination of changes of elastic-plastic properties of magnesium alloy AZ91 as cast state and after heat treatment in dependence on temperature, including investigation of fracture characteristics. It was confirmed that during heating used alloy as cast state at chosen temperatures there occurs partial dissolution of minority phases. Homogenisation of microstructure is, however, accompanied by simultaneous forming of inter-granular non-integrities, which is unfavourable from the viewpoint of strength and plastic properties, especially at higher temperatures. Failure occurs practically at all temperatures basically by inter-crystalline splitting along the boundaries of original dendrites. At temperature testing near melting point of alloy the interdendrite areas melting were observed. After application ECAP the effect of superplasticity (200-400%) was occurred. Practical implications: The results may be utilized for a relation between plastic and strength properties of the investigated material in process of manufacturing and design of these materials. Originality/value: Complex evaluation of properties magnesium alloys at higher temperatures namely for explanation of fracture mechanism near the melting point. The possibility of supperplasticity effect of Mg-Al alloys was not presented yet.

5

The structure and properties of chosen metals after ECAP

75%

Greger M. , Kocich R. , Čížek L. , Dobrzański L. A. , Widomská M. , Kuřetová B. , Silbernagel A.

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tom Vol. 18, nr 1-2

103--106

EN

Purpose: This paper was aimed at verification of functionality of the ECAP technology at extrusion of the copper, alluminium alloys and steel. Design/methodology/approach: Experiments were made on equipment, which is demonstrated in the Fig 1. Deformation forces were measured during extrusion, resistance to deformation was calculated and deformation speed was determined approximately. Analysis of structure was made with use of light microscopy and TEM. Findings: The samples of Cu and Al alloys were extruded at room temperature. For the samples of steel was used the two-stage pressing, when the samples were extruded at temperature of approx. T1 = 325°C and T2 = 220°C. In order to increase concentration of deformation in volume of the sample the samples were after individual passes turned around their longitudinal axis by 90 o and they were extruded again. Research limitations/implications: research were limited to the die with constant extrusions angless within the value of 90°. In the future, it is planne to analyse the influence of changes of the angle and relative reduction ration on the ECAP process. Originality/value: Cross-section of original samples of Cu and Al alloys was 8 x 8 mm and their length was 32 mm and cross-section of original samples of Fe alloy was 10 x 10 mm and their length was 40 mm.