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Models of damage mechanism of glidcop Cu-Al2O3 micro and nanomaterials

Besterci M., Sülleiová K., Ballóková B., Velgosová O.

Journal of Achievements in Materials and Manufacturing Engineering

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2015

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Vol. 69, nr 2

79--85

EN

Purpose:of this paper was to analyze the fracture mechanism before and after ECAP in the Glidcop AL-60 grade (with 1.1 wt. % of Al2O3) system and to propose damage and/or fracture mechanisms models by means of the method “in situ tensile test in SEM”. Design/methodology/approach: The method of “in-situ tensile testing in SEM” was used for investigations of fracture mechanisms because it enables to observe and document deformation processes directly, thank to which the initiation and development of plastic deformation and fracture can be reliably described. Analyses of microstructure and fracture surfaces were carried out by means of the scanning electrone microscope JEM 100 C. Findings: The deformation and fracture mechanisms of Glidcop AL-60 grade with 1.1 wt. % of Al2O3 phase (1.62 vol. % of Al2O3) were analyzed before and after ECAP (Equal Channel Angular Pressing). Before ECAP it was shown that the deformation process causes increasing of pores and formation of cracks. Decohesion of small Al2O3 particles and clusters occurs and the final fracture path is influenced by coalescence of cracks originated in such. The principal crack propagates towards the sample exterior surface. After ECAP initial cracks were formed in the middle of the specimen first of all in the triple junctions of nanograins and together with decohesion of Al2O3 particles and clusters at small strains lead to the failure. Research limitations/implications: To develop more complex knowledge about the objective material further studies are necessary to focus also on the other factors which besides the secondary phase amount can influence the failure mechanism, e.g. strain rate, temperature and others. Complex analysis allows better understanding of material behavior at different conditions and possibilities of application of products from these materials will be thereby improved. Practical implications: This article completes knowledge about damage/fracture mechanisms and processes of the material with 1.1 wt. % of Al2O3 phase. Some materials with the different volume fraction of a secondary phase have been studied. This concrete one with 1.1% clarifies the fracture process of Glidcop AL-60 material not only after mechanical alloying process but also after ECAP treatment. An effect of the ECAP process on the final material was crucial because not only microstructure but also failure mechanism have been changed. Originality/value: Based on the experimental observations original models of damage and/or fracture mechanisms were proposed.

2

Effects of ECAP on the mechanical properties of Mg-Al2O3 nanocomposites

Ballóková B., Besterci M., Sülleiová K., Balog M., Huang S. J.

Journal of Achievements in Materials and Manufacturing Engineering

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2015

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Vol. 69, nr 1

10--17

EN

Purpose: The purpose of this paper is the study of the effect of equal channel angular pressing (ECAP) on the mechanical properties of the Mg-Al2O3 nanocomposites. Magnesium and its alloys have excellent physical and mechanical properties for a number of applications. In particular its high strength: weight ratio makes it an ideal metal for automotive and aerospace applications, where weight reduction is of significant concern. Design/methodology/approach: Severe plastic deformation is a useful methodology to refine the grain size to the submicron or even nanometer size Findings: In the present work the influence of number of passes of ECAP by grain size, evolution of microstructure, mechanical properties and fracture of magnesium composites with different volume fraction of Al2O3 particles has been investigated by means of optical microscopy, tensile tests and scanning electron microscopy. Research limitations/implications: It has been found, that the grain size decreases with increasing number of passes. The mechanical properties of magnesium alloys are significantly influenced by the testing temperature leading to a decrease in the strength, by reinforcement and/or grain reinforcement leading to an increase in the strength. Originality/value: From previous studies, it was found that the MMCs using different size particles and different ECAP passes can improved the mechanical properties. But the research of Mg MMCs reinforcement with different wt.% nanoscale Al2O3 particles is not adequate.

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Deformation of Cu-Al2O3 composite materials

Besterci M., Lachvac J., Velgosova O., Lesko A.

Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika

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2000

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z. 54 [179]

7-10

EN

Deformation processes of Cu-Al2OS composite materials prepared via powder metallurgy are assessed in the paper. Powder mixture was prepared by grinding of Cu and Al2O3 particles. After the compaction, materials were deformed by extrusion, forging and isostatic pressing. Qualitatively were evaluated their microstructural characteristics and quantitatively their mechanical properties. By comparison of mentioned three deformation technologies it was found the isotropic microstructure in materials deformed by forging and isostatic pressing. Optimum properties (ultimate tensile strength and reduction of area) showed the materials deformed by hot isostatic pressing, which possessed low residual porosity ( <1 vol. %).