Search

Despite a huge expansion of research on compositionally complex alloys, CCA (such as the entropy alloys, HEA and the corresponding glassy alloys) their comprehension is still limited, which is detrimental both for the design of CCAs and for their application. The broad compositional range in CCAs enables simple tuning of their properties by varying the contents of their constituent elements. Accordingly, the study of transition from CCA to conventional alloy, CA composed from the same constituents is important, both for understanding the formation of solid solutions in CCAs and for proper evaluation of their potential with respect to that of CAs. However, this transition has so far been studied systematically in only two types of alloys: isopleths of the Cantor alloy and glassy TiZrNbCuNi/Co alloys with variable Co, Ni or Cu content (Materials 14 (2021) 5824 and ref. therein). In both alloy systems the variation of a given property with composition depends sharply on the selected principal component and can be either monotonic (like that in the ideal solid solution) or non-monotonic. When the variation is non- monotonic, the maximum value of the selected property is usually outside of HEA composition range.

Despite a huge expansion of research on compositionally complex alloys, CCA (such as the approximately equimolar, multi-component high- entropy alloys, HEA and the corresponding high- entropy glassy alloys), their basic understanding is still limited, which is detrimental both for the design of CCAs and for their application. In particular, the prediction of compositions capable of forming random solid solutions (RSSs) and the prediction of their properties is still a problem. Nevertheless, some properties of a few CCAs exceed those of conventional alloys (CA) [1].

Using a He3 cryostat in a superconducting magnet with fields up to 16 T, superconductivity of (TiZrNbCu)1-xNix and (TiZrNbNi)1-xCux metallic glasses was studied over a broad concentration range from the high entropy alloys (HEA) region to the Ni- and Cu-rich alloys, respectively. We have observed that the upper critical fields of these alloys are Pauli limited and that the superconducting transition temperatures follow the behaviour of the dressed density of states at the Fermi level Nγ(EF), which is common in transition metals and their alloys [1]. In particular, we have shown that the electron-phonon coupling constant λe-p is proportional to the band density of the state at the Fermi level in our alloys, but also crystalline HEAs [2-4], and in other transition metal alloys. This addresses the problem of unusual superconductivity behaviour [4] which was attributed to the chemical complexity of HEAs but is shown to be inherent to transition metals. Although, minor complications do arise from combining metals of different transition series. [1] R. C. Dynes, C. M. Varma, J. Phys. F Met. Phys. 6 (7) (1976) L215-L219 [2] P. Koželj et al, Phys. Rev. Lett. 113 (10) (2014) 107001 [3] S. Vrtnik et al, J. Alloy. Compd. 695 (2017) 3530– 3540 [4] F. von Rohr et al, Proc. Natl. Acad. Sci. 113 (46) (2016) E7144–E7150

In metallic systems electronic structure determines almost all their properties. Therefore, a change in properties of multicomponent alloys on crossing from HEA to conventional alloy concentration range in the same alloy system reflects the corresponding change in ES.

The study of transition from conventional concentrated alloys to high-entropy ones composed from the same elements is apparently very important, both for understanding the formation of HEAs and for proper evaulation of their potential with respecct to that of corresponding CAs.

We present the results of ongoing comprehensive study of the electronic properties of (TiZrNbCu)1- xNix metallic glasses performed in a broad composition range x encompassing both, the high entropy (HE) range, x ≤ 0.25, and conventional Ni- base alloy concentration range, x ≥ 0.35. The electronic structure (ES) studied by photoemission spectroscopy and low temperature specific heat (LTSH) [1] reveal the split-band structure of the density of states (DoS) inside the valence band with the d- electron of Ti, Zr, Nb and also Ni present in DoS at the Fermi level N(EF), whereas LTSH and present magnetoresistivity results show that variation of N(EF) with x changes in Ni-base regime. The variation of the superconducting transition temperatures, TC ≤ 1.6 K with x closely follows that of N(EF) as is usual in disordered transition metal alloys [2]. The electrical resistivities of all alloys are high (> 150 µΩ cm) and accordingly decrease with increasing temperature over most of the explored temperature range, and their temperature dependence seems dominated by the weak localization effects over a broad temperature range (10 – 300 K). The preliminary study of the Hall effect shows that the Hall coefficient RH > 0 and in the HE concentration range change little with x. The results are compared with these for corresponding binary metallic glasses. [1] I. A. Figueroa, et al., J. Alloys Compd. 745, 455 (2018) [2] E. Tafra, et al., J. Phys.: Condens. Matter 20, 425215 (2008)

The formation of transition metal compounds (TC) in selected devitrified high-entropy (HE) and conventional metallic glasses (MG) has been studied by using X-ray diffraction (XRD) and magnetic susceptibility (χ) measurements. The alloys selected were Al0.5TiZrPdCuNi [1], (TiZrNbL)1-xMx (L = Cu, Ni ; M = Fe, Co, Ni, Cu) [2] HEMGs, as well as conventional binary and ternary MGs containing early (TE) and late (TL) transition metals, such as the Ti, Zr, Hf – L [3] and Zr-Cu-Al alloys. Such study provides a comparison between the crystallization patterns in TE-TL HEMGs and these in conventional MGs with the same constituents, which can help to understand the differences in glass forming ability (GFA) between HEMGs and conventional MGs [2, 3]. The measurements of χ on both as-cast and crystallized alloys provide an insight into the changes of electronic structure (ES) accompanying transition from amorphous to crystalline (TCs) state, which seem to determine GFA of TE-TL alloys [3]. Further, the values of χ for crystallized alloys, χc, enable in principle the determination of χc values corresponding to particular TCs. These χc (TC) values in addition to giving an insight into contribution of given TC to ES also enable the determination of the fractions of TCs in a given alloy. This is important for a quantitative analysis of the phase contents in alloys in which the crystalline texture make the determination of phase contents from XRD less accurate. Wherever possible we compare and combine our data with the results from literature. _____________________________________________ ∗ This work was supported by UNAM-DGAPA-PAPIIT project No. IN101016 and Osijek University project IZIP2016-3. † [1] A. Takeuchi et al, Mater. Trans. 54 (2013) 776 ; [2] K. Biljaković et al., J. Alloys Compd. 695 (2017) 2661 and I. A. Figueroa et al., submitted to J. Alloys Compd. ; [3] R. Ristić et al., EPL 114 (2016) 17006 and E. Babić et al., submitted to Phil. Mag..

Rapidly cooled atomic and molecular liquids can bypass crystallization and vitrify. While network bonding in silica and chain entanglement in polymers seem plausible mechanisms for inhibiting their crystallization, the corresponding mechanism for metallic systems is less clear. When molten alloy is cooled, the formation of metallic glass (MG) usually competes with that of intermetallic compounds (IC): thus similar free energies (G) of MG and competing IC(s) facilitate vitrification. At low temperatures G is dominated with internal energy which in metallic systems strongly depends on electronic structure (ES). Thus small differences in ES between MG and competing IC(s) promote vitrification, as observed in several binary and ternary transition metal (TM) alloy systems. This correlation seems applicable to all TM alloys irrespective on their number of alloying components (thus also to high-entropy alloys) and provides a simple way to select compositions with high glass forming ability. This work was supported by UNAM-DGAPA-PAPIIT project No.IN101016 and Osijek University project IZIP2016-3

Properties of metallic glasses (MG) depend sensitively on the cooling rate (thus thickness for melt-spun ribbons). We present the effect of thickness on properties of high-entropy (TiZrNbCu)100-xNix (x≤50) and conventional binary CuxTE100-x (TE = Ti or Hf, x≤70) and ternary Cu55Hf45-x(Zr, Ti)x (x≤45) glassy ribbons. Both, as-cast and relaxed (short anneal just below glass transition temperature) samples were studied. The mechanical and vibrational properties (ultrasound velocity, Young`s modulus, microhardness, Debye temperature) of as-cast alloys showed clear effect of thickness superposed on that due to composition, whereas those of relaxed samples showed little effect of thickness. Properties of relaxed samples were larger than those of corresponding as-cast alloys and in ternary Cu55 Hf45-x(Zr, Ti)x alloys the effect of relaxation was larger for x=Ti than for Zr which may indicate the interplay between α- and β-relaxations in Cu– base MGs. The effect of cooling rate on mechanical properties provides simple criterion for glass forming ability.

On cooling of molten alloy the formation of metallic glass (MG) competes with that of intermetallic compounds (TC). This competition determines glass forming ability (GFA) of a given alloy and in binary alloys GFA can be expressed in terms of the formation enthalpies of MG and competing TCs [1]. More recently we have shown that a similar electronic structure, ES, (represented by the density of states (DoS) at the Fermi level, N(EF)) of competing TCs to that of MG enhances GFA in Cu-Hf, Zr alloys [2]. In particular, we found that small difference between the N(EF)-dependent properties (such as magnetic susceptibility (χ) and Sommerfeld coefficient (γ)) of as-cast and crystallized MGs reflects an enhanced GFA. Combining our and literature results for N(EF) and χ we show here that this correlation holds in all binary (Cu, Ni-Ti, Zr, Hf) and ternary (Cu-Hf-Ti, Cu-Zr-Al) alloys of early (TE) and late (TL) transition metals for which there exist relevant data. The correlation between ES and GFA shows up the best in Cu-Zr and NiZr2 alloys in which the data for change in N(EF) upon crystallization exist. The applicability of this correlation (GFA criterion) to all TE-TL alloys is supported by photoemission studies and low temperature specific heat measurements [3] which show similar composition dependencies irrespective of the number of components in the alloy. _____________________________________________ ∗ This work was supported by UNAM-DGAPA-PAPIIT project No. IN101016 and Osijek University project IZIP2016-3. † [1] R. Ristić et al., J. Alloys and Compd. 621 (2015) 136 ; [2] K. Biljaković et al., J. Alloys Compd. 695 (2017) 2661 ; [3] R. Ristić et al. EPL , 114 (2016) 17006.

Recent studies of Cu55Hf45-xTix metallic glass (0 ≤ x ≤ 45) [1] indicate the formation of bulk metallic glass (BMG) for 15 ≤ x ≤ 30. In the same compositional range ratio of the glass transition temperature Tg and the temperature of liquid state Tl shows slight maximum consistent with the greatest glass forming ability (GFA). A recent study of the magnetic susceptibility and mechanical properties (Young's modulus and microhardness) showed a uniform change of these properties with x without any special features in the compositional range where the BMGs form [2]. We will present the results of measurement of the electrical resistivity and the Hall coefficient of these alloys as a function of concentration and temperature (80K ≤ T ≤ 300K). These properties, closely related to the electronic structure and dynamics of electrons, monotonously depend on x and show no special features in the area of BMGs. The temperature dependence of resistances is consistent with the effects of the weak initial localization of electrons.The Hall coefficients (RH) are positive, practically independent of temperature and grow approximately linearly with x. So, neither RH nor electrical resistance indicates the formation of BMG. As studied alloys have the same number of electrons per atom e/a, it cannot be associated with BMG formation. [3]. [1] I. A. Figueroa, H. A. Davies, I. Todd, I. A. Verduzco, P. Hawksworth, Adv. In Tech. of Met. and Mat. Proc. J. 8 146-151 (2006) ; [2] R. Ristić, E. Babić, D. Pajić, K.Zadro, I. A. Figueroa, H. A. Davies, I. Todd, A. Kuršumović, J. Alloys Compd. 504S (2010) S194-S197 ; [3] M. Fukuhara, M. Takahashi, Y. Kawazoe, I. Inoue, Appl. Phys. Lett. 90 (2007) 073114.

High-entropy alloys (HEA) are new type of alloys based on multiple (≥5) principal alloying elements [1). This design enables research and probable exploitation of a huge number of new alloys with structures and properties which can hardly be anticipated [2]. For obvious reason and also due to often inadequate strategy of research [3], the conceptual understanding of HEA is quite limited which hampers their development. After brief introduction in HEA we present main results of a parallel study of local atomic structure, electronic structure (including first ever photoemission spectroscopy study of HEA) and selected properties of (TiZrNbCu)1-xNix (x≤0.5) amorphous alloys, which sheds more light into their interrelationship and also enables direct comparison of HEA with conventional Ni-rich alloys (x≥0.35). Our results challenge some myths commonly employed in descriptions of HEA [2]. [1] B. Cantor, I. T. H. Chang, P. Knight, A. J. B. Vincent, Mat. Sci. Eng. A 375-377 (2004) 213. [2] E. J. Pickering, N. G. Jones, Inter. Mater. Rev. 61 (2016) 183, and references therein. [3] K. Biljaković et al , J. Alloys Compd. 695 (2017) 2661.

Većina konvencionalnih slitina sastoji se od jednog, ili u rijetkim slučajevima dva, osnovna metala kojima se dodaju male količine drugih metala i/ili nemetala kako bi se poboljšala njihova svojstva. U posjednih nekoliko godina veliku pažnju pak privlači novi tip slitina, tzv. slitine visoke entropije (eng. High-entropy alloys - HEA). Ove slitine su građene od velikog broja (=>5) elemenata u približno ekvimolarnom omjeru [1, 2]. Ovakva građa otvara potencijal za istraživanje velikog broja novih slitina raznih struktura i svojstava [3]. Nedavno su objavljeni rezultati [4] opsežnih istraživanja četiri (TiZrNbCu)_1-xNi_x(x

Recent study of the electronic structure and properties of (TiZrNbCu)1-xNix (x≤0.25) amorphous high entropy alloys (a-HEA [1]) has been extended to x=0.5 in order to compare the behaviours of a- HEA and a conventional Ni-base metallic glasses (MG). All samples were ribbons about 20 μm thick and their fully amorphous state was verified by thermal analysis and X-ray diffraction (XRD). XRD patterns were also used in order to deduce the nearest neighbour distances and probable local atomic arrangements [1, 2]. Precise composition and the distribution of components were studied with a scanning electron microscope (SEM) with an energy dispersive spectroscopy (EDS) attachment. Here we studied thermal parameters (the glass transition temperature Tg, the first crystallisation temperature Tx and the melting and liquidus temperatures Tm and Tl respectively), the low temperatures specific heat (LTSH [1]), the magnetic susceptibility χexp and the Young's modules E. Except for E which was measured both for as-cast and relaxed ribbons (after a short anneal close to Tg) all other properties were measured on as-cast samples only. The LTSH showed that the electronic density of states of the Fermi level N(EF) decreases with increasing x, whereas the Debye temperature ΘD increases with x [1]. This is similar to what observed in binary and ternary MGs [2, 3] of early transition metals (TE) with late transition metals and indicates that N(EF) is dominated with the d-electrons of TE . Like ΘD , E, Tx and Tl increased with increasing x indicating the enhanced inter- atomic bonding on addition of Ni (similar to that observed in binary TE-Ni MGs [2, 4]). However Tx and Tl tend to saturate for x≥0.25 which seems to support a change in local atomic arrangement around x=0.25 deduced from the analysis of XRD patterns. The usual parameters associated with glass forming ability (GFA) showed little variation with x, thus no real change in GFA when going from a-HEA to conventional MGs in the studied system. As expected [1], the rule of mixtures gave poor description for most properties of our alloys. 1. K. Biljaković et al, J. Alloys Compd. 695, 2661 (2017). 2. R. Ristić et al, J. Alloys Compd. 621, 136 (2015). 3. R. Ristić et al, Solid State Commun. 151, 1014 (2011). 4. R. Ristić , M. Stubičar, E. Babić, Phil. Mag. 87, 5629 (2007).

A comprehensive study of selected properties of (TiZrNbCu)1-xNix (x≤0.5) glassy alloys has been performed. The samples were ribbons about 20 μm thick and their fully amorphous state was verified by X-ray diffraction (XRD) and thermal analysis (DSC/DTA). The surface morphology, actual composition and the distribution of components were studied with Scanning electron microscope with an energy dispersive spectroscopy attachment. The properties studied were average interatomic distances and probable atomic short range order (SRO), thermal stability parameters, low temperature specific heat (LTSH), the magnetic susceptibility χ and the Young’s modulus. The XRD results for x≤0.25 (high entropy alloys, HEA) indicated [1] a bcc-like SRO (similar to that in corresponding crystalline HEA with x≤0.2 [2]), and the behaviour of their properties was similar to that observed in binary Ti, Zr- Ni, Cu glassy alloys [3]. In particular, electronic density of states at the Fermi level (dominated with d-states of TiZrNb [4]) and χ decreased on increasing x, whereas the properties associated with interatomic bonding (thermal, vibrational and elastic parameters) increased with increasing x. An extension of this study to x≤0.5 indicates a change in SRO from bcc-like to fcc-like for x≥0.25 (which is consistent with valence electron number, VEC≥7 criterion for stability of fcc structure in crystalline HEA [1]) which strongly affects the variation of all physical properties with x in these alloys. Here, we discuss parameters derived from XRD and DSC/DTA analyses. The glass forming ability and the applicability of the rule-of- mixtures are also briefly discussed. [1] K. Biljaković et al , J. Alloys Compd.. 695 (2017) 2661. [2] A. Cunliffe, J. Plummer, I. Figueroa, I. Todd, Intermetallics 23 (2012) 204. [3] R. Ristić, J. R. Cooper, K. Zadro, D. Pajić, J. Ivkov, E. Babić , J. Alloys Compd. 621 (2015) 136. [4] U. Mikšić., P. Pervan, UPS results, private comm. (2017).

Dosadašnje istraživanje elektronske strukture (TiZrNbCu)1-xNix (x≤0.25) amorfnih visokoentropijskih slitina (a-HEA [1]) prošireno je do x=0.5 s namjerom da usporedimo ponašanje a- HEA i standardnih metalnih stakala (MG) s Ni. Uzorci su bile trakice oko 20 μm tanke, a amorfno stanje je provjereno termičkom analizom i difrakcijom X-zraka (XRD). XRD dijagrame upotrijebili smo za izračunavanje udaljenosti najbližih susjeda i lokalnog uređenja [1, 2]. Točniju kompoziciju i distribuciju komponenata izučavali smo sa skenirajućim elektronskim mikroskopom (SEM) s dodatkom za energijski disperzivnu spektroskopiju (EDS). Ovdje istražujemo termičke parametre (temperature staklastog prijelaza Tg, temperature prve kristalizacije Tx, temperature taljenja Tm i temperature tekućeg stanja Tl), niskotemperaturni specifični toplinski kapacitet (LTSH [1]), magnetsku susceptibilnost χexp i Youngove module E. E smo mjerili za as-cast i relaksirane trake (nakon kratkog aniliranja blizu Tg), a sva ostala svojstva mjerili smo samo na as-cast uzorcima. LTSH pokazuje da elektronska gustoća stanja na Fermijevom nivou N(EF) opada s povećanjem x, dok Debye-eva temperatura ΘD raste s x [1]. Slično ponašanje uočili smo u binarnim i ternarnim MG [2, 3] između ranih prijelaznih (TE) i kasnih prijelaznih metala (TL) koje pokazuje da je N(EF) pretežno određena s TE d-elektronima. ΘD , E, Tx i Tl rastu s x pokazujući porast međuatomskih veza dodavanjem Ni (slično kao u binarnim TE-Ni MG [2, 4]). Međutim Tx i Tl teže zasićenju za x≥0.25 pa se čini da opisuju promjenu u lokalnoj strukturi oko x=0.25 koja slijedi iz analize XRD dijagrama. Uobičajeni parametri pridruženi sposobnosti ostakljivanja (GFA) pokazuju malu promjenu s x, no nema stvarne promjene u GFA kada idemo od a-HEA prema standardnim MG u promatranim sustavima. Kako smo i očekivali [1], pravilo smjese ne daje dobar opis za mnoga svojstva naših slitina. 1. K. Biljaković et al, J. Alloys Compd. 695 (2017) 2661 2. R. Ristić et al, J. Alloys Compd. 621 (2015) 136 3. R. Ristić et al, Solid State Commun. 151 (2011) 1014 4. R. Ristić , M. Stubičar, E. Babić, Phil. Mag. 87 (2007) 5629

A comprehensive study of the electronic structure and properties of (TiZrNbCu)1-xNix (x≤0.25) amorphous high-entropy alloys (a-HEA [1]) has been extended to x=0.5 in order to compare the behaviours of a-HEA and a conventional Ni-base metallic glasses (MG). All samples were ribbons about 20 μm thick and their fully amorphous state was verified by thermal analysis and X-ray diffraction (XRD). XRD patterns were also used in order to deduce the nearest neighbour distances and probable local atomic arrangements (SRO)[1, 2]. Precise composition and the distribution of components were studied with a scanning electron microscope (SEM) with an energy dispersive spectroscopy (EDS) attachment. Here we discuss thermal parameters (the crystallization enthalpies ΔHx, the glass transition temperature Tg, the first crystallisation temperature Tx and the melting and liquidus temperatures Tm and Tl respectively), the magnetic susceptibility χexp and the Young's modulus E. The analysis of XRD patterns indicates a change in SRO from body centered cubic (bcc)-like towards face centered cubic (fcc)-like for x>0.25 (which is consistent with the valence electron number criterion, VEC

Recently we reported a correlation between the change in magnetic susceptibility upon crystallization of Cu-Zr, Hf metallic glasses and glass forming ability (GFA) in these alloys [1]. In particular we have shown that a small difference in magnetic susceptibilities of corresponding amorphous and crystalline alloys reflects high GFA (represented by high value of the reduced glass transition temperature Trg=Tg/Tl , where Tg and Tl are the glass transition and liquidus temperatures, respectively). Further, we have shown that this correlation stems from similar electronic structures, ES (represented by the electronic density of states at the Fermi level, N(EF)) of amorphous and corresponding crystalline alloy [1, 2]. Here we extended a study of this correlation by investigating the magnetic susceptibilities over a broad composition range in several Ti-Cu, Zr-Cu and Zr-Ni alloys. In particular we studied a change of magnetic susceptibility upon crystallization in five Ti-Cu and four selected Zr-Cu and Zr-Ni metallic glasses. Actual compositions of Zr-Cu and Zr-Ni alloys were selected to complete and verify the literature results for these alloy systems [3, 4]. The methods employed for magnetic susceptibility measurements and crystallization of studied alloys were the same as in our previous report [1]. The fully crystalline final state of all our alloys was verified by x-ray diffraction patterns. An important novel feature of a present study is that we use the experimental critical casting thickness dc which is directly related to GFA to describe the variation of GFA with composition in Ti-Cu, Hf-Cu and Zr-Cu alloys. (Since for Zr-Ni alloys dc data do not exist we described the variation of GFA in these alloys by using the empirical GFA criteria such as Trg.) For all four studied alloy systems, very good correlation between dc and / or other criteria for high GFA and the change in magnetic susceptibility upon crystallization of metallic glasses has been obtained. The correlation between ES and GFA in these alloys also showed up the best in Zr-Cu alloys (where also the data for the change in N(EF) upon crystallization are available [2]) and in Zr2Ni alloy which exhibits a local maximum in GFA due to virtually no difference between N(EF) of metallic glass and corresponding intermetallic compound. The applicability of this criterion for GFA (which provides a simple way to select the composition with high GFA) to other metal-metal metallic glasses (including ternary and multicomponent bulk metallic glasses) is briefly discussed. 1. R. Ristić et al, EPL 114, 17006 (2016). 2. P. Garoche and J. Bigot, Phys. Rev B 28, 6886 (1983). 3. Z. Altounian, T. Guo-Hua and J. O. Strom- Olsen, J. Appl. Phys. 53, 4755 (1982). 4. Z. Altounian, T. Guo-Hua and J. O. Strom- Olsen, J. Appl. Phys. 54, 3111 (1983).

Naše ranije proučavanje svojstava amorfnih nemagnetskih TL - TE slitina (TL = Ni, Cu ; TE = Ti, Zr, Hf) u širokom području koncentracija (30 - 70 at % TL) omogučilo nam je da linearnom ekstrapolacijom podataka za slitine odredimo parametre vezane uz atomsku i elektronsku strukturu i svojstva čistih amorfnih TE [1]. Ovdje pokazujemo da se u slučaju TL = Cu isti podaci mogu koristiti da se ekstrapolacijom odrede svojstva i atomska struktura čistog amorfnog Cu (koji je eksperimentalno nedostupan). To je povezano sa iznenađujućim važenjem Vegardovog zakona za atomske volumene amorfnih Cu - Ti, Zr slitina [2], koje smo proširili i na Cu - Hf slitine. Ovisno o svojstvu, vrijednosti za amorfni Cu su ili blizu onim za kristalni Cu (termodinamička ravnotežna svojstva) ili blizu onim za tekući Cu ekstrapoliranim na sobnu temperaturu (elektronska transportna svojstva). Pouzdanost dobivenih rezultata se ogleda i u tomu da se neovisno o izboru TE, sve ovisnosti proučavanih svojstava ekstrapoliraju u istu vrijednost za amorfni Cu [3]. Dobiveni rezultati su važni za razumijevanje amorfnih TL - TE slitina (uključujući i razumijevanje uvjeta nastanka masivnih metalnih stakala u tim sustavima). Literatura: [1] R. Ristić, E. Babić, D. Pajić, K. Zadro, A. Kuršumović, I.A. Figueroa, H.A. Davies, I. Todd, L.K. Varga, I. Bakonyi, J. Alloys Compd., 504S (2010) S194. [2] I. Bakonyi, Acta Materialia, 53 (2005) 2509. [3] R. Ristić, J.R.Cooper, K. Zadro, D. Pajić, J. Ivkov, E. Babić, J. Alloys Compd., 621 (2015) 136.

Being unstable in respect to both crystalline and ideal glassy state the properties of metallic glasses (MG) depend sensitively on the preparation conditions (thus thickness for melt - spun ribbons). We present first measurements of the effect of thickness (i.e. quenching rate) on the properties of CuxTE100-x (TE = Ti or Hf, x ≤ 70) and Cu55 Hf45-x(Zr, Ti)x (x ≤ 45) glassy ribbons. Both, as-cast and relaxed (short anneal just below glass transition temperature, Tg) samples were studied. The mechanical properties (ultrasound velocity, Young`s modulus, microhardness) of as-cast alloys showed clear effect of thickness superposed on that due to variation in composition (x), whereas those of relaxed samples showed no effect of thickness. As expected, the mechanical properties of relaxed samples were higher than those of corresponding as-cast alloys and in ternary Cu55 Hf45-x(Zr, Ti)x alloy the effect of relaxation was larger for x = Ti than for Zr which may indicate the interplay between nearly overlapping α- and β- relaxations in Cu– base MGs [1]. Since the effect of thickness distorts the compositional variations of properties in the as-cast MGs (Fig. 1), this may lead to erroneous conclusions [2]. [1] H.- B. Yu, W.-H. Wang, K. Samwer, Mater. Today 16 (2013) 183 –191. [2] R. Ristić et al., J. Alloys Comp. 621 (2015) 136-145 and reference therein.

TE‐TL (TE=Ti, Zr, Hf and TL=Ni, Cu) alloys show wide glass‐forming ranges which enables detailed study of the change in the electronic structure and properties on alloying and, thus a thorough comparison between the model and experimental data. Amorphous TETL alloys have been extensively studied in recent decades and interest in these alloys further increased after the discovery of TE‐TL based bulk metallic glasses (BMGs). In amorphous TE‐TL alloys the properties that are directly related to the electronic density of states (DOS) often show linear variations with TL content. The effect of alloying with TL can be approximated by the dilution of amorphous TE. Thus , one can extrapolate the data for glassy TE‐TL alloys to zero TL content in order to deduce the properties of amorphous TE (also in Cu‐TE alloys we extrapolate data to zero TE to deduce the properties of amorphous Cu). The magnetic susceptibility was measured with a SQUID magnetometer MPMS in a magnetic field B

Static and dynamic magnetic behaviour of Hf100−xFex (20 ≤ x ≤ 90) metallic glasses in the temperature range 1.5–300 K and magnetic fields up to 5.5 T reveal some important conclusions about the chemical order. For 25 ≤ x ≤ 43 the magnetic susceptibility increases rapidly with x due to the onset of magnetic correlations in the vicinity of the transition into the ferromagnetic state, xc~50. However, for 35 ≤ x ≤ 43 the alloys consist of self-assembled magnetic nanoclusters embedded within a paramagnetic matrix. This was concluded after study of the slow dynamics of magnetization and characteristic behaviour of ac- susceptibility, which were explained with the thermal activation of magnetic moments of the nano-clusters over the anisotropy barriers. These clusters grow rapidly with increasing x. In this way, magnetic method showed as very convenient in indicating the evolution of chemical order on nanometer scale. Altogether, Hf–Fe glassy alloys evolve from the superconducting and paramagnetic through the superparamagnetic to the ferromagnetic state with increasing iron content. This might be of relevance for other systems with the non-trivial magnetic behaviour.

We start with a brief review of progress in research and applications of metallic glasses (MG) over last 60 years. The milestones, such as their discovery, fabrication of bulk MGs (BMG) and the progress in commercialization of MGs will be emphasized. Next, we briefly review early research of rapidly quenched alloys in Zagreb and fruitful collaboration in this research between Zagreb and Sarajevo (initiated by Professors B. Leontić and E. Girt in 1969.) We show that till 1990. the research and fabrication of MGs in Zagreb and Sarajevo was at the forefront of research in this field. This showed very clearly at the EC‐Yu Colloquium on Advanced Materials, held in September 1988. in Sarajevo. We compare some predictions from this Colloquium with the present achievements in the field of MGs. Further, we outline the impact of the discovery of BMGs in 90‐ties (at first in multicomponent and then in binary transition metal alloys) on the further development of this field of research . We will use binary BMGs (which are the base of more important multicomponent BMGs) in tackling still unsolved problem of the origin of high glass forming ability (GFA), which enables the formation of BMGs. Some largely ignored features of binary Cu‐Ti, Zr, Hf MGs, such as ideal solution behaviour are emphasized and their relation with GFA and formation of BMGs in Cu‐ Zr, Hf alloys is proposed. On the basis of previous results for Cu‐Zr MGs we propose a novel criterion for selection of potential BMG forming alloys, which may apply to multicomponent systems based on transition metals, too.

Magnetic transitions in materials are often much more complicated than are the examples from the cook-books of magnetism. Therefore, additional measurements should always be performed in order to develop the realistic model of magnetic state of the system. One way of distinguishing between the magnetic states is via dynamics of the dc magnetization after change of outer conditions, i.e. the magnetic field or temperature. Magnetic transitions in multiferroic family of K3Fe5F15 and similar compounds motivated us to study the slow relaxation of magnetization of these materials on the hours time scale after change of magnetic field. This slow process was described by a logarithmic time dependence over a broad temperature and field range, similar to the behaviour of magnetic nanoparticles. The results were explained with thermal activation of magnetic moments of the magnetic nanoregions in crystal over the anisotropy barriers. Thus, from magnetization measurements the sizes of magnetic regions were estimated to be in the nanometre range, that should be of importance for the multiferroicity and magneto-electric coupling. Conducted reasoning was enlighten knowing magnetic behaviour of the nanoparticles, where slow relaxation of the magnetization comes from the activation of their magnetic moments over the anisotropy barriers. Surprisingly, in our studied FeNiB amorphous nanoparticles, both coated in SiO2 and uncoated, the relaxation of magnetization deviated from this simple picture. However, this deviation and comparison with the geometrically determined size distribution indicate that the magnetic units responsible for the observed dynamics consist of several physical nanoparticles. Similarly, the slow magnetic relaxation appeared in system of Hf100−xFex metallic glasses. For 35≤x≤43, which is above the paramagnetic regime and below the onset of the ferromagnetic state, observed behaviour was explained with the self-assembled magnetic nano-clusters embedded within a paramagnetic matrix. This reveals uniquely the development of the chemical order showing that the clusters grow rapidly with increasing x. In this way, magnetic method showed as very convenient in indicating the evolution of chemical order on nanometre scale. In three presented cases applicability of slow magnetic relaxation method teaches us how to use it for study of the nano-magnetic inhomogeneities in wide class of different materials with thenon-trivial magnetic behaviour.

Properties of nonmagnetic amorphous TE-TL alloys (TE=Ti, Zr, Hf ; TL=Ni, Cu) have been studied over a broad concentration range in order to estimate the parameters associated with the electronic and atomic structure in pure amorphous Ti, Zr and Hf [1]. We achieved this by extrapolating approximately linear variation of the data for alloys to zero TL content. Here we show that the same data can also be used to obtain the properties of pure amorphous cooper. This is correlated with the validity of the Vegard´s law for atomic volumes in amorphous Ti-Cu and Zr-Cu alloys [2] which extends also to Hf-Cu alloys. The reliability of results is supported by the fact that irrespective of TE, the variations of all studied properties of amorphous TE-Cu alloys extrapolate to the same value for amorphous Cu. Depending on a particular property, their values are either close/somewhat below those for crystalline copper, or are close to those of liquid copper. As already noted, the electronic transport properties extrapolate to those of liquid Cu, whereas the electronic density of states, the Debye temperature and the Young´s modulus are close or little lower than those of crystalline Cu. As expected, the microhardness, Hv , of amorphous Cu is much larger than that of crystalline copper due to absence of extended defects. The results are discussed in some detail and their impact on present understanding of amorphous TE-TL alloys (which is crucial for understanding of formation of bulk metallic glasses) emphasized.

We have investigated the low temperature heat capacity of Cu55Hf45‐xTix metallic glasses in the entire range of Ti concentrations, x=0‐45. We have established the most appropriate procedure for the analysis of data and for the estimate of low temperature electronic and phonon contributions. Both contributions exhibit monotonous Ti concentration dependence, demonstrating that there is no relation of either the electron density of states at the Fermi level or the Debye temperature to the increased glass forming ability (GFA) in the Ti concentration range x=15‐30. Our results indicate that the thermodynamic parameters (e.g. reduced glass temperature) remain the most assertive indicators of GFA for bulk metallic glasses. However, we discuss the possibility to correlate more subtle glass‐like contributions to the heat capacity, such as the Boson peak, with GFA.