Ondrej Milkovič

Nanostructure Formation and Properties in Some Al Alloys after SPD and Heat Treatment

Influence of SPD process realized by ECAP on structural formation and mechanical properties was searched. Samples after ECAP were heat treated at various temperature and time conditions. Investigation material bases were high purity aluminium and aluminium alloys EN AW 6082, EN AW 2014. The best material properties are describing in dependence on experimental conditions.

Local structure of explosively welded titanium–stainless steel bimetal

Abstract Bimetals targeted for industrial applications are usually designed to combine the properties of two dissimilar metals, e.g. high strength, high hardness and low cost of steels with chemically resistive titanium. In this work the structure of one particular, but for industries very interesting, bimetallic system – Cr/Ni stainless steel clad with titanium has been studied. The material was prepared by explosion welding, a method capable of joining a wide variety of similar or dissimilar materials. Our analysis is based on X-ray micro-diffraction experimentation utilizing hard monochromatic X-rays focused down to micrometer size. In this way the bimetal in bulk form was analyzed and microstructural differences between the joined materials and their interface were determined.

Influence of Hot Plastic Deformation in γ and (γ + α) Area on the Structure and Mechanical Properties of High-Strength Low-Alloy (HSLA) Steel

The main goal of this study was to develop a new processing technology for a high-strength low-alloy (HSLA) steel in order to maximize the mechanical properties attainable at its low alloy levels. Samples of the steel were processed using thermal deformation schedules carried out in single-phase (γ) and dual-phase (γ + α) regions. The samples were rolled at unconventional finishing temperatures, their final mechanical properties were measured, and their strength and plasticity behavior was analyzed. The resulting microstructures were observed using optical and transmission electron microscopy (TEM). They consisted of martensite, ferrite and (NbV)CN precipitates. The study also explored the process of ferrite formation and its influence on the mechanical properties of the material.

The Influence of Severe Plastic Deformation on Structure and Mechanical Properties the Aluminium Alloy EN AW 6082

The effect of severe plastic deformation by ECAP process on the microstructures and mechanical properties of the aluminium alloy EN AW 6082 produced by cold extrusion is investigated. In both states were evaluated the structural changes by light microscopy, the analysis particles in structures, by X-ray diffraction (XRD) in transmission mode by synchrotron radiation and mechanical properties. Severe plastic deformation leads to strengthening of investigated EN AW 6082 alloy but on the other hand the plasticity of ECAP-ed alloy decreases.

Study on electrochemical properties of Pd-C and Pd-CNT catalysts

ABSTRACTThe catalytic and electrochemical properties of carbon-supported Pd catalysts (Pd-C, Pd-CNT), prepared by the technique of deposition reduction, are presented in this paper. Single-walled a...

Microstructure Changes and Improvement in the Mechanical Properties of As-Cast AlSi7MgCu0.5 Alloy Induced by the Heat Treatment and ECAP Technique at Room Temperature

The changes in the microstructure and improvement in the mechanical properties of as-cast AlSi7MgCu0.5 alloy induced by the heat treatment and technique of equal channel angular pressing (ECAP) were investigated. The heat treatment of as-cast alloy performed before the ECAP technique was required to increase the plasticity of the alloy. Therefore, the samples of analysed alloys were solution annealed at optimized temperature of 823 K for 4 hours to dissolve the particles of intermetallic π(Al8FeMg3Si6) phase and to spheroidize the Si particles. Subsequently, water quenching and artificial ageing at optimized temperature of 573 K for 5 hours was used to obtain an overaged alloy state. The microstructure of alloy was consisted of α(Al) solid solution, eutectic Si particles, and intermetallic β(Mg2Si), Q-Al4Mg5Si4Cu, α-Al12(Fe,Mn)3Si, and/or α-Al15(Fe,Mn)3Si2 phase particles. The crystal structure of present phases was confirmed by hard X-ray diffraction at Deutsches Elektronen-Synchrotron (DESY) in Hamburg and by the selected area electron diffraction (SAED) performed inside the transmission electron microscope (TEM). The heat-treated alloy was processed by ECAP at room temperature following route A. Repetitive ECAP of alloy homogenized the heterogeneous as-cast microstructure and formed the ultrafine subgrain microstructure with elongated subgrains of 0.2 µm in width and 0.65 µm in length and the high dislocation density. Microstructural changes in alloy induced by both heat treatment and ECAP led to the high strain hardening of the alloy that appeared in an improvement in strength, ductility, and microhardness of alloy in comparison with as-cast alloy state.

Influence of Nanoparticle Size on Strain at the Core-Shell Interface

This work deals with the strain at the core-shell interface of Fe nanoparticles. Series of Fe nanoparticles with various mean diameters were prepared by precipitation in solid state in binary Cu-Fe alloy. Further, nanoparticles were isolated by dissolution of Cu matrix. High-energy X-ray diffraction (XRD) was used to probe structure of nanoparticles. XRD measurements suggest presence of the core-shell structure, where core and shell of the nanoparticles are formed of α-Fe and CuFe2O4 phase, respectively. Strains in core and shell were estimated as a function of nanoparticles size by Williamson-Hall method.

Structure Characterisation of Electrodeposited Ni-Co Alloy

This paper is focused to structure characterization of two differently electrodeposited Ni-Co alloys on the copper surface. The chemical composition of the layers was determined by the EDX analysis in the scanning electron microscope. Phase analysis was realized by diffraction in the transmission mode using synchrotron radiation. Diffraction patterns also show the preferred orientation in the coating with saccharine addition.

Effect of Technologies Processing on Material Properties of Selected Aluminium Alloys

The paper is concerned with an analysis of utility properties of selected aluminium alloys, namely EN AW 6082 (AlSi1MgMn), EN AW 6061 (AlMg1SiCu) and EN AW 7075 (AlZn5.5MgCu) with different technology of hot processing. The alloys were hot processed to reach T3 condition (solution annealing, cold forming and natural aging) and to reach T4 condition (solution annealing and natural aging). The following parameters were subject to evaluation: microstructure and sub-structure, mechanical properties (strength and plastic characteristics stated in Table. 1) as well as fatigue properties of these alloys assessed during alternative symmetrical stress in torsion. The paper was aimed to study the affect of processing technology of three aluminium alloys on their utility properties in the conditions of tensile stress and cyclic stress in torsion.

Structural Properties of Ni-Co Electroplated Coatings Studied by X-Ray Micro-Beam

In this article we focused to influence of current density on the structure parameters evaluated by microdiffraction experiment in transmission mode using synchrotron radiation. For this purpose the coatings of Ni-Co alloy were deposited on the Cu substrate using different current densities during the electrodeposition process. The results of the microdiffraction experiment showed the structure uniformity of the coatings along their thickness, as well as changes in the structure parameters depending on the used current density during the deposition process.