Bostjan Markoli

• PhD
• Vice Rector at University of Ljubljana

Rolls are the most critical yet vulnerable parts of cold rolling mills. It is crucial for them to withstand long rolling campaigns without losing surface roughness or incurring damage. Newly developed rolls are made from tool-grade steel with high roughness, lower wear, and high damage resistance. One of the most important advantages is the elimina...

The main objective was to investigate and evaluate the influence of TiC and TiB2 inoculants on the formation of not only the icosahedral quasicrystalline phase (IQC) but also the β-phase in our Al-Mn-Si-Cu-Mg alloy. First, the presence of both phases was confirmed using electron backscatter diffraction (EBSD), followed by microstructural segmentati...

Rolls are the most critical yet vulnerable parts of cold rolling mills. It is crucial for them to withstand long rolling campaigns without losing surface roughness or incurring damage. The newly developed rolls are made from tool-grade steel with high roughness, lower wear, and high damage resistance. One of the most important advantages is the eli...

Electrochemical water-splitting is a promising green technology for the production of hydrogen. One of the bottlenecks, however, is the oxygen evolution half-reaction (OER), which could be overcome with the development of a suitable electrocatalyst. Recently, non-noble metal, high-entropy oxides (HEO) have been investigated as potential OER electro...

This study confirms that crystalline TiB2 particles can act as a potent site for the heterogeneous nucleation of the metastable icosahedral quasicrystalline phase (IQC) formed in cast Al-Mn-Si-Cu-Mg alloys. The results show that a primary metastable IQC phase nucleates on facets of TiB2 particles. Electron backscatter diffraction patterns and selec...

A number of Al-Mn-based alloys were investigated with a view to their commercialization. Various casting techniques were used to affect the constitution of the alloys studied from crystalline to quasi-crystalline as well as other metastable states. Variations in cooling rates and chemical composition, along with other processing parameters, have be...

This work deals with the characterisation of the micro-structure of a nickel insert, a special copper alloy and the cast joint between them after their use as a glass manufacturing mould. The microstructure was characterised by optical microscopy, scanning electron microscopy and microanalysis by energy dispersive X-ray spectroscopy. It was found t...

This paper deals with the characterization of three different commercial, WC-Co cemented-carbide tools in the form of saw blades, one group of which exhibits more frequent cracking. Since the properties of these materials largely depend on the microstructure, a detailed characterization was carried out using scanning electron microscopy (SEM), ener...

Alloys of the quasibinary section Cu –NiBe were experimentally investigated with differential thermal analysis, optical microscopy, electron microanalysis, transmission electron microscopy and X-ray diffraction. The construction of the quasibinary Cu–NiBe phase diagram was made based on the experimental results. The constitution of alloys of the wh...

To evaluate the effect of homogenization conditions on the possible loss of low-melting-point Pb and Bi to the surface in the free-cutting AA6026 alloy, three homogenization regimes were applied: 480°C/12 h, 530°C/12 h, and 550°C/6 h. The microstructural characterization by optical, scanning, and transmission electron microscopy coupled with EDS an...

This study focused on the crystal and electronic structures of a newly discovered phase in the Al-Cr-Sc system. The latter two species do not mix in a binary alloy, but can be alloyed with aluminium in the vicinity of the Al2−xCrxSc composition, where 0.3 < x < 0.5. After preparation of the pure constituents via arc melting, high-temperature anneal...

This work deals with the influence of gallium addition on the constitution and formation of the phases in the Al-rich corner of the Al–Mn system during casting. Al-rich binary Al–Mn and ternary Al–Mn–Ga alloys were cast into a copper mould with a cavity diameter of 5 mm. The microstructures of the produced alloys were characterized by scanning elec...

The present study investigates the effect of shot peening (SP) on the mechanical properties and surface roughness of 7075 aluminum alloy during different stages and conditions of heat treatment. The mechanical properties were determined by measuring Vickers microhardness profiles and residual stress profiles, while the amount of alloying elements p...

The paper describes the production of an AlSi7Mg cast alloy with Li additions and the reactions of the melt with different moulding materials. It is known that Li is very reactive and tends to form various reaction products such as oxides, gases, etc., which can influence the casting quality. The aim of the research was to find a suitable way to pr...

We propose a dominant core-shell formation mechanism for grain-boundary-diffusion-processed (GBDP), Tb-treated, Nd2Fe14B sintered magnets. A depth-sensitive analysis of Tb-treated samples, relative to a non-GBDP Nd2Fe14B magnet, showed a 30% increase of the coercivity in the central part of the magnet. A structure-chemistry-magnetic-property analys...

Lithium additions to Al offer the promise of substantially reducing the weight of alloys, since each 1 wt. % Li added to Al reduces density by 3 % and increases elastic modulus. In the present work, the effect of 1.46 wt. % Li addition to AlSi7Mg (containing 7.05 wt. % Si and 0.35 wt. % Mg) was studied. The alloy showed reduced density and higher h...

This investigation deals with the influence of calcium, strontium and zinc on the formation of primary, metastable quasicrystals in Al-Mn-Si alloys as these can enhance the mechanical properties of alloys. The synthesized alloys were cast into a copper mould. The castings were characterized using standard tools for studying microstructure. The Al-M...

This work deals with the influence of alloying elements on the cooling rate and microstructure in complex Al–Mn-based alloys. Alloys were synthesized at 880 °C and cast into a copper mould with cylindrical casting cavity. The castings were characterized by light microscopy (LOM), scanning electron microscopy (SEM) and energy-dispersive x-ray spectr...

This study confirms that the stable icosahedral quasicrystal (iQc) phase Al65Cu20Fe15 (iQc–AlCuFe) can serve as a substrate for the nucleation of the metastable iQc–AlMnSi phase formed in rapidly solidified Al–Mn–Si alloys. The results reveal that a continuous, thin layer of the metastable iQc–AlMnSi phase can be formed on a stable iQc–AlCuFe parti...

An Al–Mn alloy with additions of copper, magnesium, and silicon was prepared and cast into a copper mold. It contains in situ-formed icosahedral quasicrystals (iQCs), as confirmed by electron backscatter diffraction. The aim of this work is to present the mechanical and corrosion properties of this alloy and compare its properties with some convent...

The study compared environmental footprints of two types of Al-alloys: well-known 5083 aluminium alloy with magnesium and traces of manganese and chromium in its composition. This material is highly resistant to seawater corrosion and the influence of industrial chemicals. Furthermore, it retains exceptional strength after welding. The comparisons...

We prepared three Al–Mn-based alloys with different copper, magnesium and silicon contents by casting into cylindrical copper molds. All the alloys exhibited primary metastable quasicrystals (QCs). In order to confirm the presence of either primary decagonal QCs (dQCs) or icosahedral QCs (iQCs) and to determine their compositions, the castings were...

A new test rig for thermal fatigue testing was used to investigate and characterise surface layer degradation of indefinite chill double pour (ICDP) cast iron hot work roller. Thermal fatigue tests were performed at three temperatures (500 °C, 600 °C and 700 °C) using a Gleeble 1500D thermomechanical simulator. Appearance of cracking was evaluated...

X-ray phase analysis (XRD), differential thermal analysis (DTA) and X-ray fluorescence spectroscopy (XRF) of pyrite samples in a protective (Ar) and an oxidative atmosphere (air) at different temperatures (200, 300, 500, 700) °C and times (1, 2, 4) h were made. A graphical representation of the unit cell of magnetic pyrrhotite and diffraction patte...

The present work describes the formation of amorphous alloys in the (Al1−xCex)62Cu25Fe13 quaternary system (0 ≤ x ≤ 1). When the amount of Ce falls in the range 0.67 ≤ x ≤ 0.83, the alloys obtained exhibit a completely amorphous structure confirmed by powder X-ray diffraction. Otherwise, at compositions x = 0.5, 0.58, 0.92 and 1, a primary crystall...

The development of advanced materials and technologies based on magnetocaloric Gd and its compounds requires an understanding of the dependency of mechanical properties on their underlying microstructure. Therefore, the aim of the study was to characterize microstructural inhomogeneities in the gadolinium that can be used in magnetocaloric refriger...

From a corrosion perspective, aluminum and its alloys have been a successful materials used for many applications like commodity roles, automotive and vital structural components in aircrafts, and numerous Al-based alloys are successfully used in different environmental or atmospheric conditions in their conventional metallurgical forms. In this pa...

Pure copper and Cu−11.4 wt.%Au alloy were obtained by a powder metallurgy (PM) technique and subjected to thermomechanical treatment that was used to produce the conditions that led to an anneal hardening effect in the alloy. The results showed that low-temperature annealing of cold-rolled alloy caused a two-stage increase in hardness, microhardnes...

An experimental study was carried out on cold worked Cu-12.7 wt.%Au alloy and pure copper, in order to compare the properties change during thermo-mechanical treatment. Hardness, microhardness, and electrical conductivity were studied as a function of annealing temperature and annealing time with the purpose of investigating the intensity of anneal...

Recognizing quasicrystals that are embedded in Al-based cast alloys is a challenging task. For this reason, we synthesized a series of multi-component, AlMn-based alloys that contain many icosahedral quasicrystals in addition to crystalline phases. We then conducted a thorough investigation in order to unambiguously distinguish the quasicrystalline...

Aluminium alloys with primary icosahedral quasicrystals (iQCs) were prepared in this work. Alloys of Al-Mn-Cu-Mg-Si with different content of manganese were prepared in chamber furnace and cast into a copper mould with 5 mm diameter. Light microscopy (LM) was used for the characterization of microstructure and evaluation of possible presence of QCs...

Recognizing quasicrystals that are embedded in Al-based cast alloys is a challenging task. For this reason, we synthesized a series of multi-component, AlMn-based alloys that contain many icosahedral quasicrystals in addition to crystalline phases. We then conducted a thorough investigation in order to unambiguously distinguish the quasicrystalline...

In this study we investigated the microstructural changes after a variety of heat treatments of the quasicrystalline Al - Mn - Be - Cu alloy. In addition, we report on Vickers microhardness measurements and tensile-test results for the same materials. The samples were produced in a conventional manner, i.e., melting in an electrical resistance furn...

This paper presents the results of a study on the possibility of replacing cutting inserts and introducing dry-cutting mode (without water rinsing) with a chainsaw machine in the underground structures of the Hotavlje I quarry. In the experiment a column-driven chainsaw machine Fantini G.70 was used with tungsten-carbide-based cutting inserts. The...

Paper presents the results on the corrosion behavior of some Al-Fe-Si, Al-Mg-Si and Al-Mg-Mn alloys in their final commercially usable tempered state. Durability of alloys was quantified and compared in the sense of corrosion rates in aqueous solutions while also having in mind the role of alloy chemistry. Open circuit corrosion potential (OCP) mea...

The effect of the chemical composition, i.e. content of silicone (Si) and other alloying elements (Zr, Mn, etc) on the corrosion behaviour and mechanical properties of Al-Mg-Si (6xxx) type alloys was investigated in this paper. Open circuit corrosion potential (OCP) measurements, linear polarization and potentiodynamic anodic/cathodic polarization...

Fe–Pd nanowires were synthesised in anodic alumina templates by applying both potentiostatic and pulsed electrodeposition regimes. When using potentiostatic deposition, only fragmented nanowireswere obtained; however, the use of pulse deposition was shown to be effective for producing solid nanowires. In order to achieve this, different on-times fo...

This paper deals with the characterization of a polymer-matrix composite support beam designed for the automotive industry. The discussed composite polymer-matrix material was characterized using light microscopy (LM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Vickers hardness (HV) measurements and mechanical t...

Due to their good corrosion resistance, favorable mechanical properties, and reasonable price regarding their excellent properties, austenitic stainless steels have, over recent decades, become one of the alloys that are increasingly used in civil engineering and building, as well as for specific architectural purposes. Architects often design stai...

Aluminum-based alloys have been used extensively for the past five decades primarily due to their good strength vs. specific weight ratio. Numerous methods and techniques have been devised to further improve mechanical properties of these alloys as they are often used in the transport applications. Influence of the cooling rate and chemical composi...

We report on nitrogen-filled hollow Co-Pt nanospheres produced via pulsed-laser ablation in ambient nitrogen gas. The resulting nanospheres are characterized by a single-crystalline face-centred cubic Co55 +/- 3Pt45 +/- 3 shell and a void filled with molecular nitrogen, typically occupying the sphere's central region. The average diameter of the sp...

An Al-based cast alloy containing Mn, Be and Cu has been chosen to investigate the room temperature deformation behavior of QC particles embedded in Al-matrix. Using LOM, SEM (equipped with EDS), conventional TEM with SAED and controlled tensile and compression tests, the deformation response of AlMn2Be2Cu2 cast alloy at room temperature has been e...

This work investigated the constitution of the Al-rich corner within the ternary Al-Mn-Be phase diagram using SEM + EDS, AES, XRD and DSC. With respect to the results, an isothermal cross-section at 600 degrees C was established, as well as a prediction of the apparent liquidus projection in the Al-corner. Be4AlMn is a thermodynamically stable phas...

of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

Due to the fact that grain size measurement in metallic materials is of great importance, five well known and established grain size measurement methods were compared for accuracy and time consumption, i. e.: comparison method, intercept method, planimetric method (by Jeffries), planimetric delineation method performed in semiautomatic manner and a...

This work studied the phases in the Al corner of the Al-Mn-Be phase diagram in the as-cast state and heat-treated conditions. Metallographic investigations, X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy were used for identifying the phases. The Be contents in the identified phases were precisely determined usin...

This article presents the cause(s) of a relatively increased wear and failure of cutting tools during the final treatment of a central housing made of pearlitic (grey) cast iron with lamellar graphite. Castings with a proper (designated asšgood') and an inadequate (designated as šbad') microstructures were investigated. Chemical analyses showed a h...

In this work, an Al-Mn-Be-Cu alloy was prepared by vacuum induction melting and casting. The alloy was then remelted and gravitationally cast into cylindrical metallic dies with 2 mm, 4 mm and 8 mm diameters in order to obtain the quasicrystalline phase in the aluminium-rich matrix. The samples with height-to-thickness ratio of 3:1 were tested usin...

In this study the effect of the cooling rate on the microstructure of Al94Mn2Be2Cu2 alloy was investigated. The vacuum induction melted and cast alloy was exposed to different cooling rates. The slowest cooling rate was achieved by the DSC (10 K.min(-1)), the moderate cooling rate succeeded by casting in the copper mould (approximate to 1 000 K.s(-...

The aim of the present investigation was to determine and to compare the superplastic behaviour of the AA5083 (Al-Mg-Mn) alloy with Sc and Zr additions. The investigated alloys were processed to form sheets by conventional hot and cold rolling. The superplastic properties were determined with strain rates in the range of 1x10-4 to 5x10-2s-1 and for...

In this study the eff ect of the cooling rate on the microstructure of Al 94Mn 2Be 2Cu 2 alloy was investigated. The vacuum induction melted and cast alloy was exposed to different cooling rates. The slowest cooling rate was achieved by the DSC (10 K min -1), the moderate cooling rate succeeded by casting in the copper mould (≈1 000 K s?1) and the...

The shapes of icosahedral quasicrystalline (IQC) particles in Al-Mn-Be-(Cu) alloys were determined in samples subjected to very wide range of cooling rates: from around 106 K/s in very thin melt-spun ribbons down to below 100 K/s in permanent copper dies. Accordingly, the sizes of quasicrystalline particles ranged from few tenths of nanometres up t...

Sm-Fe-Ta-N-O nanospheres were synthesized by pulsed-laser deposition from a Sm(13.8)Fe(82.2)Ta(4.0) target in a nitrogen atmosphere. Three structurally and compositionally distinct types were identified: amorphous, core-shell and hollow nanospheres. Amorphous spheres were compositionally homogeneous and completely oxidized. The core-shell spheres w...

The microstructures of the base materials (EN 10216-1 and EN 10083-3) and three consumables (EVB 50, EVB CrMo and INOX R 29/9) were investigated in the as-welded and heat-treated states. The base material where the fracture occurred was EN 10216-1, which is why the characterization was focused only on that side of the weld. The microstructure of th...

Nanostructures of two non-oriented electrical steels were investigated in order to elucidate the influence of nanostructure and its components on magnetic properties. The main difference between the two samples was related to the mean grain size and level of core loss. Surprisingly, the sample with coarser ferrite grains exhibited higher core loss....

This paper investigated properties of dispersed phases in an Al94Mn2Be2Cu2 alloy using a microindentation hardness test. The focus was directed to the possible strengthening phases for aluminium alloys: an icosahedral quasicrystalline phase (i-phase), a hexagonal quasicrystalline approximant with a large unit cell (H-phase) and a ternary cubic Be4A...

An indentation study was performed on an experimental alloy Al 94Mn2Be2Cu2 under two as-cast conditions. The alloy was first vacuum-induction melted and then one sample was die-cast into a copper mould with a diameter of 50mm, and the other into a mould with a diameter of 3 mm. The Palmqvist cracks are found to play the most important role when det...

The solidification paths of the Al86.1Mn2.5Be11.4 and Al84Mn5.1Be10.9 alloys, melt spun, cast into a copper mould and controlled cooled (during DSC) were investigated by means of light-optical microscopy (LOM), differential scanning calorimetry (DSC) combined with thermogravimetry (TG) or simultaneous thermal analysis (STA), scanning electron micro...

Near-equiatomic Co–Pt thin films with thicknesses of 520nm were deposited from a single electrolyte onto glass-based Au-coated substrates using the electrodeposition method. The as-deposited Co–Pt-based films were annealed at temperatures from 500ºC to 700ºC for 1h. The phase formation, microstructure and the magnetic properties were analyzed. It w...

Flow stresses and activation energy of BRCMO high-speed steel has been investigated. Hot compression tests in the tempera-ture range of 900–1050 °C at strain rates of 0.001–10 s –1 and true strain of 0–0.9 were applied on Gleeble 1500D thermo-mechanical simulator. For entire hot working range the constants of the hyper-bolic sine function and activ...

An Al86Mn3Be11 alloy cast into copper mould was subjected to metallographic investigation. The as-cast microstructure consisted of a quasicrystalline icosahedral phase (i-phase), Be4AlMn phase and, occasionally, a hexagonal phase. Al-rich solid solution represented the dominant phase. The chemical compositions of phases were determined using AES. T...

Gd5Si2Ge2-based alloys can exhibit a giant magnetocaloric effect (GMCE); this gives them the potential for use in cooling technologies. It has also been reported that a small addition of iron reduces the hysteresis losses in Gd5Si2Ge2-based alloys, thus increasing the net refrigerating capacity. In this investigation, we have been the first to look...

Magnetocaloric Gd₅Si₂Ge₂-based alloys exhibit a well-documented giant magnetocaloric effect at around room temperature. However, as candidate materials for real-world refrigeration devices, they suffer from a number of problems, one of which is large hysteresis losses while cycling in and out of the magnetic field....

Several Al-alloys strengthened by quasicrystalline phases have been developed over the last few years showing the considerable potential for practical application. Therefore there is a strong need for developing new metallographic methods or adapting the traditional ones in order to identify and characterize quasicrystalline phases in a reliable, q...

An Alz94Mn2Be2Cu2 cast alloy was developed displaying increased quasicrystalline formation ability at moderate cooling rates. The as-cast microstructure consisted of a mainly icosahedral phase in the Al-matrix. The microstructure remained stable during uniform heating to 580 °C and isothermal annealing at 400 °C. Most of the icosahedral phase was p...

Microstructures of two alloys with the nominal compositions of Al92Mn3Be5 and Al89Mn6Be5 were characterized in the initial as-cast condition (after vacuum induction melting and casting) and after melt spinning. In the initial conditions, both alloys consisted of an aluminum-rich solid solution and two metastable intermetallic phases: Be4AlMn and Al...

The quasicrystalline phase in melt-spun Al-Mn-Be alloys was investigated. In ribbons 40-60 mu m thick the phase was present in the form of small particles rather uniformly dispersed in an aluminium solid solution matrix. The quasicrystalline phase had a primitive icosahedral structure. It was confirmed that it contained a substantial amount of Be....

Microstructure of the steel X20CrMoV12.1, used for thermal power plants, after tempering at approximately 500 °C consists of tempered martensite with carbide precipitates. The evolution of the chemical and phase composition of carbide precipitates in X20CrMoV12.1 steel was studied in the as-received state after 56 000 h at 470–530 °C under load and...

In the ternary system Al-Cu-Fe an i-phase (icosahedral quasicrystal) is present. It is thermodynamically stable and a part of the equilibrium phase diagram. However, according to the chemical composition and conditions during the solidification and heat treatment, a considerable number of intermetallic phases can be in stabile or metastabile equili...

Surface effects during plasma activation of poly(p-phenilene sulphide)—PPS have been studied. Samples that were exposed to weakly ionized highly dissociated oxygen plasma created an inductively coupled radiofrequency discharge with the power of 100W. The electron density and temperature were measured with a double Langmuir probe and were 4×1015m−3...

In this work we characterized the structure of continuously cast small cross-section rods (Ø10 mm) of the Ni-based superalloy GMR 235. In the microstructure prevailed dendritic columnar γ-grains with γ′-precipitates. In the interdendritic regions MC-carbide and M3B2-boride were identified. The inverse macrosegregation was very faint, except at the...

Ledeburitic chromium steel X155CrVMo12.1 for coldwork tools was investigated in the quenched and tempered condition. Using appropriate investigative methods the evolution of the microstructure in all conditions was characterized. The change in state of a multicomponent matrix during tempering is crucial for attaining the required properties of this...

Improved sample wettability was obtained by oxygen plasma functionalization of pyrolytic graphite. The samples were exposed to highly dissociated oxygen plasma with the density of 1 × 1016 m−3, the electron temperature of about 5.5 eV and the density of neutral oxygen atoms of 8 × 1021 m−3 for 20 s. The surface wettability was measured by a contact...

Magnetic micro-actuators and systems (MAGMAS) require tiny permanent magnets with dimensions of hundreds of micrometers. Such magnets need to have the highest possible energy density, which means Nd–Fe–B magnets are the most appropriate type. Most bottom-up fabrication techniques are either too slow or too expensive; top-down techniques involving m...

The evolution of the chemical and phase composition of carbide precipitates in X20CrMoV12.1 steel after long-term service of 56 000 h (470-530°C at up to 18 MPa) and after heat treatment (650 and 800°C) was investigated using transmission electron microscopy and Auger electron spectroscopy. The precipitates found were mostly of M23C6 type, the S- a...

In this work a Ni-based superalloy GMR 235 was investigated. We determined convenient metallographic methods for preparation of bulk metallographic specimens, extraction carbon replicas, transparent metallic foils and minor phase extraction. In addition, the alloy microstructure was characterised using different metallographic, techniques.

Alloys of the quasibinary section Cu-NiBe were experimentally investigated with differential thermal analysis, optical microscopy, electron microanalysis, transmission electron microscopy and X-ray diffraction. The construction of the quasibinary Cu-NiBe phase diagram was made based on the experimental results. The constitution of alloys of the who...

The Ni-based superalloy GMR 235 was investigated in different as-cast conditions. It consisted of the gamma matrix with gamma' precipitates, and of three minor constituents: M3B2, MC and Ti(C,N). The cooling rate influenced the size and morphology of microstructural constituents, and the composition and lattice constants of M3B2, and MC. (C) 2002 A...

The constitution of alloys and the liquidus surface in the Al-rich corner of the Al-Si-Sm ternary system were determined by the examination of controlled heated and cooled specimens, as well as heat-treated specimens by means of optical and scanning electron microscopy, energy-dispersive X-ray spectroscopy, differential thermal analysis and X-ray d...

The constitution of the alloys in the; silicon-rich tamer of the Si-Sm phase diagram was examined, using optical microscopy, differential thermal analysis, scanning electron microscopy, X-ray diffraction, and microhardness measurements. The microstructure of the hypoeutectic alloys showed the presence of the primary crystallized silicon anti binary...

Gd5Si2Ge2-based alloys can exhibit a giant magnetocaloric effect (GMCE); this gives them the potential for use in cooling technologies. It has also been reported that a small addition of iron reduces the hysteresis losses in Gd5Si2Ge2-based alloys, thus increasing the net refrigerating capacity. In this investigation, we have been the first to look...