Bulk metallic glasses represent a newly developed class of materials. Some metallic glasses possess combinations of very good or even excellent mechanical, chemical and/or magnetic properties uncovering a broad range of both industrial and vital applications. Besides all advantages metallic glasses have also significant drawbacks, which have to be overcome for commercial application. Apart from low critical thicknesses, brittleness and chemical inhomogeneity one important problem of metallic glasses is the lack of an appropriate theory describing their structure. Therefore, the search for new glass forming compositions as well as the improving of existing ones occurs at present by means of trial-and-error methods and a number of empirical rules. Empirical rules for good glass-forming ability of bulk metallic glasses have been established in recent years by Inoue and Egami. Two of these rules, (i) Preference of more than 3 elements and (ii) Need of more than 12 % radii difference of base elements, seem to be closely related to topological (geometrical) criteria. From this point of view topological parameters contribute essentially to the glass-forming ability. The third rule (iii) demands a negative mixing enthalpy of base elements and refers to the chemical interaction of the atoms. The generalized Bernal’s model (hard-sphere approximation) was used for the simulation of monatomic, binary and multi-component structures. Excluding chemical interaction, this method allows the investigation of topological criteria of the glass-forming ability. Bernal’s hard-sphere model was shown to be a good approximation for bulk metallic glasses and metallic liquids and yields good coincidence of experimental and theoretical results. • The Laguerre (weighted Voronoi) tessellation technique was used as the main tool for the structural analysis. Due to very complex structures it is impossible to determine the structure of bulk metallic glasses by means of standard crystallographic methods. • Density, radial distribution function, coordination number and Laguerre polyhedra analysis confirm amorphism of the simulated structures and are in a good agreement with available experimental results. • The ratio of the fractions of non-crystalline to crystalline Laguerre polyhedra faces was introduced as a new parameter . This parameter reflects the total non-crystallinity of a structure and the amount of atomic rearrangements necessary for crystallization. Thus, the parameter is related to the glass-forming ability. It depends strongly on composition and atomic size ratio and indicates a region of enhanced glass-forming ability in binary mixtures at 80 % of small atoms and atomic size ratio of 1.3. All found maxima of parameter for ternary mixtures have compositions and size ratios which are nearly the same as for the binary mixture with the maximum value of . • A new method of multiple-compression was introduces in order to test the tendency towards densification and/or crystallization of the simulated mixtures. The results of the multiple-compression of monatomic mixtures indicate a limiting value of about 0.6464 for the density of the amorphous state. Further densification is necessarily connected to formation and growth of nano-crystalline regions. • The results of the multiple-compression for binary mixtures shows a new maximum of the density at the size ratio of 1.3 and 30 % to 90 % of small atoms. This maximum indicates a local island of stability of the amorphous state. The maximal receivable density without crystallization in this region is enhanced compared to neighbouring regions. • The comparison of the parameter and the density to the distribution of known binary bulk metallic (metal-metal) glasses clearly shows that both parameters play a significant role in the glass-forming ability. • The polyhedra analysis shows regions with enhanced fraction of the icosahedral short-range order (polyhedron (0, 0, 12)) in the binary systems with the maximum at 80 % of small atoms and size ratio of 1.3. Comparison of the distribution of the (0, 0, 12) polyhedra to the distribution of known binary metallic (metal-metal) glasses and to the parameter shows that icosahedral short-range order is not related to the glass-forming ability and is a consequence of the high non-crystallinity (high values of ) of the mixtures and non vice versa. Results for the ternary mixtures confirm this observation. • A new approach for the calculation of the mixing enthalpy is proposed. The new method is based on the combination of Miedema’s semi-empirical model and Laguerre tessellation technique. The new method as well as 6 other methods including the original Miedema’s model were tested for more than 1400 ternary and quaternary alloys. The results show a better agreement with experimental values of the mixing enthalpy for the new model compared to all other methods. The new model takes into account the local structure at atom site and can be applied to all metallic alloys without additional extrapolations if the atomic structure of the considered alloy is known from a suitable atomistic structure model.

Os vidros metálicos baseados em Cu-Zr representam uma classe bastante promissora para a categoria de materiais estruturais, tendo em vista suas interessantes propriedades resultantes da natureza amorfa. Sabe-se que o oxigênio tem grande influência na formação da estrutura amorfa e consequentemente nas propriedades dessa classe de materiais. No presente trabalho, ligas amorfas baseadas em Cu-Zr foram analisadas termicamente a fim de se observar o comportamento das mesmas frente à contaminação com oxigênio. As análises térmicas foram realizadas em um equipamento de calorimetria exploratória diferencial (DSC), e as temperaturas características como de transição vítrea, cristalização, fusão e líquidus foram determinadas. Concluiu-se que conforme a literatura apresenta, o processo de cristalização é favorecido pela presença de oxigênio, causando uma queda na energia de ativação dos processos de cristalização das ligas trabalhadas. Através de ensaios que simularam tratamentos térmicos, cristalizou-se controladamente as amostras amorfas baseadas em Cu-Zr a fim de formar compósitos entre cristais e vidros metálicos buscando diminuir a fragilidade das ligas. / Cu-Zr-based bulk metallic glasses represent a very promising class of structural materials with interesting properties resulting from the amorphous nature. It is known that oxygen has a great influence on the formation of the amorphous structure and consequently on the properties of these materials. In the present work, Cu-Zr-based amorphous alloys were thermally analyzed in order to observe their behavior against oxygen contamination. Thermal analyzis were performed on a differential scanning calorimetry (DSC) equipment, and characteristic temperatures as glass transition, crystallization, melting and liquidus were determined. It was concluded that, according to the literature, the crystallization process is favored by the presence of oxygen, causing a decrease in the activation energy of the crystallization processes of the worked alloys. Through tests that simulated heat treatments, the amorphous samples were crystallized in order to form composites between crystals and metallic glasses in order to reduce the brittleness of the alloys.

Les verres métalliques massifs sont connus pour leurs propriétés de résistance mécanique supérieures par rapport aux matériaux cristallins, mais aussi par une fragilité macroscopique. Cependant, des effets d’échelle sur le comportement mécanique ont été parfois reportés de manière inattendue lors de la réduction des tailles des échantillons. Afin d’étudier de tels effets, on s’est intéressé aux propriétés mécaniques de films minces en verre métallique de composition Zr65Ni35 et d’épaisseurs entre 200 et 900 nm ; les films étant obtenus par pulvérisation cathodique. Le comportement mécanique de ces films a été étudié à la fois sur substrat Si et sur des films libres. On montre que les films avec composition Zr65Ni35 ont la même structure atomique comme indiqué par l'absence de décalage des pics de diffraction et par des valeurs constantes de la densité, des propriétés élastiques, et du volume d'activation. Cependant, les mécanismes de fissuration varient avec l’épaisseur du film sur substrat, mais que cette variation résulte essentiellement d’un effet de confinement de l’épaisseur sur le développement de la zone plastique. Les propriétés mécaniques des films libres ont été étudiées en utilisant notamment une technique originale de micro-traction actionnée par contrainte interne. Dans ces conditions, des déformations plastiques importantes (jusqu’à 10%) combinées à des niveaux de contraintes élevés (jusqu’à 3500 MPa) ont pu être obtenues et on a montré qu’un paramètre important dans le contrôle des propriétés était l’aire de la section du film pouvant influencer la capacité d’obtention d’une percolation des défauts mis en jeu lors de la déformation plastique. Cela a été confirmé par des valeurs constantes du volume d’activation, estimé en étudiant les phénomènes de relaxation de la contrainte. L'effet de la composition du film sur les propriétés mécaniques a également été analysé et, dans ce cas, les variations de comportement mécanique ont été reliées à des modifications de la structure atomique du verre métallique. / Bulk metallic glasses are known for their superior strength performances with respect to crystalline counterparts, but also for a macroscopically brittle behaviour. Nevertheless, mechanical size effects have surprisingly been reported when reducing the specimen dimensions. In order to study such effects, the mechanical properties of thin Zr65Ni35 metallic glass films – deposited by DC magnetron sputtering – have been investigated for thickness ranging from 200 up to 900 nm. The mechanical behavior was studied for films deposited on Si substrate and for freestanding films as well. Zr65Ni35 films exhibit the same atomic structure as indicated by the absence of shift of diffraction peaks and by the constant values of the mass density, elastic properties, and activation volume. However, the cracking mechanisms of the film on the substrate are thickness dependent, resulting from a thickness confinement effect on the development of the plastic zone. The mechanical properties of freestanding films were investigated using an original technique of micro-tension controlled by internal stresses. Homogeneous plastic strains (up to 10 %) combined with very high stresses (up to 3500 MPa) were attained. The specimen cross-sectional area was the key parameter affecting the probability to get percolation of defects involved in the plastic deformation as confirmed by the constant value of the activation volume estimated analyzing stress relaxation phenomena. The effect of the composition on the mechanical properties has been investigated as well and, in this case, the changes in mechanical behavior were preferentially attributed to modifications of the metallic glass atomic structure.

L'objectiu de la tesi és estudiar la cinètica de les cristal·litzacions primàries en vidres metàl·lics mitjançant simulacions de tipus phase field. Una cristal·lització primària és una transició de fase sòlid-sòlid on la fase que cristal·litza (fase transformada o fase secundaria) té una composició química diferent de la fase precursora (fase no transformada o fase primària).Les dades experimentals obtingudes a partir de l'estudi calorimètric de cristal·litzacions primàries s'analitzen generalment en el marc del model KJMA (Kolmogorov, Johnson & Mehl, Avrami). Aquest model proporciona l'evolució temporal de la fracció transformada basant-se en tres hipòtesis: - Els nuclis de la fase secundaria estan distribuïts aleatòriament en tot l'espai.- El creixement d'aquests nuclis és isotròpic.- El creixement s'atura únicament per xoc directe (hard impingement).En la cristal·lizació de vidres metàl·lics s'ha observat experimentalment un alentiment de la cinètica respecte del comportament calculat emprant la citada cinètica KJMA. Aquest alentiment s'explica a la literatura en base a que en aquest tipus de transformacions, controlades per difusió, la interacció entre els cristalls no és directa sinó que es produeix a través dels perfils de concentració (soft impingement) i, a més, l'evolució d'aquests perfils de concentració causa canvis en la concentració de la matriu amorfa, estabilitzant la i per tant fent que la nucleació de nous cristalls esdevingui no aleatòria. Diversos autors han proposat modificacions del model KJMA per tal d'intentar superar aquestes limitacions, basats bé en consideracions geomètriques, bé en aproximacions de camp mitjà. A pesar de tot, cap d'aquests models és capaç d'explicar satisfactòriament la cinètica observada en cristal·litzacions primàries. L'objectiu d'aquest treball ha estat la simulació realista de la cinètica de les transformacions primàries per trobar una explicació consistent a les diferències observades entre les dades experimentals i els models teòrics disponibles.Per tal de poder descriure de forma realista el procés de cristal·lització primària s'ha d'estudiar el procés de nucleació i creixement de la fase secundaria alhora que es resol l'equació de difusió en la fase primària. En aquest treball s'ha emprat un model de simulació phase field que permet estudiar aquest sistema introduint una nova variable lligada al camp de concentració que pren dos valors diferents segons es tracti de fase transformada o no transformada. Amb aquest tipus de models també es poden introduir diferents protocols de nucleació i per tant estudiar independentment els efectes de la nucleació en la cinètica. D'aquesta manera s'han realitzat simulacions en 2 i 3 dimensions de cristal·litzacions primàries amb diferents graus de fracció transformada final). Els resultats de les simulacions s'ha comparat amb el model KJMA i, contra el que es preveia, s'ha obtingut un bon acord entre les fraccions transformades del model KJMA i de les simulacions. Donat que el model KJMA no reprodueix satisfactòriament el comportament experimental d'aquest resultat es dedueix que ni el soft impingement ni la nucleació no aleatòria son les responsables de l'alentiment de la cinètica obtingut en cristal·litzacions primàries. Per tal de trobar una explicació físicament convincent del comportament observat experimentalment s'ha aprofundit en l'estudi teòric de les cristali·litzaciones primàries, incloent-hi l'efecte dels canvis composicionals que tenen lloc en la matriu a mesura que la transformació es produeix. Aquest fet, tot i ser conegut a la bibliografia, ha estat sistemàticament ignorat en l'elaboració de models cinètics. En concret, s'ha fet palès que canvis en la composició química de la fase primària han d'afectar de forma radical a la viscositat, que varia fortament a prop de la transició vitrea, i han de produir canvis en les propietats de transport atòmic. Això s'ha modelat a través de l'assumpció d'un coeficient de difusió depenent de la concentració, en base a la relació modificada d'Stokes-Einstein entre la viscositat i el coeficient de difusió. Les simulacions phase-field amb un coeficient de difusió d'aquest tipus donen lloc a una cinètica més lenta i que mostra un acord excel·lent amb la cinètica experimentalment observada en cristal·litzacions primàries de vidres metàl·lics. Per tant, les simulacions phase field confirmen que la cinètica de les cristal·litzacions primàries està controlada fonamentalment pel canvi en les propietats de transport atòmic, mentre que els efectes de soft impingement i nucleació no aleatoria, tot i estar presents, son secundaris. / El objetivo de la tesi es estudiar la cinética de las cristalizaciones primarias en vidrios metálicos mediante simulaciones de tipo phase field. Una cristalización primaria es una transición de fase sólido-sólido donde la fase que cristaliza (fase transformada o fase secundaria) tiene una composición química diferente a la fase precursora (fase no transformada o fase primaria).Los datos experimentales obtenidos a partir del estudio calorimétrico de cristalizaciones primarias se analizan generalmente en el marco del modelo KJMA (Kolmogorov, Johnson & Mehl, Avrami). Este modelo proporciona la evolución temporal de la fracción transformada basándose en tres hipótesis: - Los núcleos de la fase secundaria están distribuidos aleatoriamente en todo el espacio- El crecimiento de estos núcleos es isotrópico- El crecimiento se detiene únicamente por choque directo (hard impingement).En la cristalización de vidrios metálicos se ha observado experimentalmente un retardo de la cinética respecto del comportamiento calculado usando la cinética KJMA. Este retardo se explica en la literatura en base a que en este tipo de transformaciones, controladas por difusión, la interacción entre los cristales no es directa sino que se produce a través de los perfiles de concentración (soft impingement) y, además, la evolución de estos perfiles de concentración causa cambios en la concentración de la matriz amorfa, estabilizándola y por tanto haciendo que la nucleación de nuevos cristales sea no aleatoria. Varios autores han propuesto modificaciones del modelo KJMA para intentar superar estas limitaciones, basados bien en consideraciones geométricas, bien en aproximaciones de campo medio. A pesar de todo, ninguno de estos modelos es capaz de explicar satisfactoriamente la cinética observada en cristalizaciones primarias. El objetivo de este trabajo ha sido la simulación realista de la cinética de las transformaciones primarias para hallar una explicación consistente a las diferencias entre los datos experimentales y los modelos teóricos disponibles.Para describir de manera realista el proceso de cristalización primaria se tiene que estudiar el proceso de nucleación y crecimiento de la fase secundaria a la vez que se resuelve la ecuación de difusión en la fase primaria. En este trabajo se ha usado un modelo de simulación phase-field que permite estudiar este sistema introduciendo una nueva variable ligada al campo de concentración que toma dos valores diferentes según se trate de fase transformada o no transformada. Con este tipo de modelos también se pueden introducir diferentes protocolos de nucleación y por tanto estudiar independientemente los efectos de la nucleación en la cinética. De esta manera se han realizado simulaciones en 2 y 3 dimensiones de cristalizaciones primarias con diferentes grados de fracción transformada final. Los resultados de la simulaciones se han comparado con el modelo KJMA y, en contra de lo que se preveía, se ha obtenido un buen acuerdo entre las fracciones transformadas del modelo KJMA y de las simulaciones. Dado que el modelo KJMA no reproduce satisfactoriamente el comportamiento experimental, de este resultado se deduce que ni el soft impingement ni la nucleación no aleatoria son las responsables del retardo en la cinética obtenido en cristalizaciones primarias.Para encontrar una explicación físicamente convincente del comportamiento observado experimentalmente se ha profundizado en el estudio teórico de las cristalizaciones primarias, incluyendo el efecto de los cambios composicionales que tienen lugar en la matriz a medida que la transformación se produce. Este hecho, aún y ser conocido en la bibliografía, ha sido sistemáticamente ignorado en la elaboración de modelos cinéticos. En concreto, se ha hecho patente que cambios en la composición química de la fase primaria tienen que afectar de forma radical a la viscosidad, que varía fuertemente cerca de la transición vítrea, y tienen que producirse cambios en las propiedades de transporte atómico. Esto se ha modelado a través de la asunción de un coeficiente de difusión dependiente de la concentración, en base a la relación de Stokes-Einstein modificada entre la viscosidad y el coeficiente de difusión. Las simulaciones phsae-field con un coeficiente de difusión de este tipo dan lugar a una cinética más lenta y que muestra un acuerdo excelente con la cinética experimentalmente observada en cristalizaciones primarias de vidrios metálicos. Por tanto, las simulaciones phase-field confirman que la cinética de las cristalizaciones primarias está controlada fundamentalmente por los cambios en las propiedades de transporte atómico, mientras que los efectos de soft-impingement y nucleación no aleatoria, aún y estar presentes, son secundarios. / The aim of this thesis is to study the kinetics of primary crystallization in metallic glasses by means of phase-field simulations. A primary crystallization is a solid-solid phase transformation where the crystallized phase (transformed phase or secondary phase) has a chemical composition different than the precursor phase (untransformed phase or primary phase).Experimental data from calorimetric studies of primary crystallization are usually studied in the framework of the KJMA model (Kolmogorov, Johnson & Mehl, Avrami). This model yields the temporal evolution of the transformed fraction on the basis of three main assumptions: - A random distribution of particle nuclei of the secondary phase- The growth of these nuclei is isotropic- The growth is only halted by direct collisions (hard impingement).In the crystallization of metallic glasses, a slowing down of the kinetics respect the behavior calculated with the KJMA kinetics has been observed. This delay is explained in the literature by the fact that in this kind of transformations, that are diffusion controlled, the interaction between the crystals is not direct but through the concentration profiles (soft impingement) and moreover, the evolution of these profiles causes changes in the concentration of the amorphous matrix, stabilizing it and thus, the nucleation of new nuclei become non random. Several authors had proposed modifications to the KJMA model to try to overcome these limitations, based either on geometrical considerations or in mean field approaches. However, none of these models is able to explain the observed kinetics in primary crystallizations. The aim of this work has been the realistic simulation of the kinetics of primary crystallization to find a explanation to the differences between the experimental data and the available theoretical models.In order to describe in a realistic way the process of a primary crystallization, the nucleation and growth process of the secondary phase has to be studied at the same time that the diffusion equation is solved in the primary phase. In this work, it has been used a phase field model for the simulations that allows to study this system introducing a new variable, coupled to the concentration field, that takes two different values in each of the existing phases. With these kinds of models, different nucleation protocols can also be introduced and thus, independently study the effects of the nucleation in the kinetics. Therefore, 2 and 3 dimensional simulations of primary crystallization have been performed with several degrees of final transformed fraction. The simulation results have been compared with the KJMA model and, unexpectedly, a good agreement between the simulations and the KJMA model has been obtained. As the KJMA model does not reproduce satisfactorily the experimental behavior, from this result can be deduced that neither the soft impingement nor the non random nucleation are the responsible of the slowing down observed in the kinetics of primary crystallization.In order to find a physical convincing explanation of the observed experimental behavior, the theoretical study of primary crystallization has been extended, including the effects of the compositional changes that take place in the matrix as the transformation proceed. This fact, notwithstanding being known in the literature, has been systematically ignored in the development of the kinetics models. In particular, it has become clear that changes in the chemical composition of the primary phase have to radically affect the viscosity, that strongly varies near the glass transition, and some changes in the atomic transport properties must occur. This has been modeled through the assumption of a compositional dependent diffusion coefficient, on the basis of a modified Stokes-Einstein relation between viscosity and diffusion coefficient. Phase field simulations with a diffusion coefficient of this type yield a slower kinetics and show an excellent agreement with the kinetics experimentally observed in primary crystallization of metallic glasses. Thus, phase field simulations confirm that the kinetics of primary crystallization is fundamentally controlled by the changes in the atomic transport properties, while the soft impingement and non random effects, although being present, are secondary.

The aim of this study is to investigate the bulk glass forming ability (BGFA) of Ti-based alloy systems. These investigations were carried out in two main parts that are complementary to each other: theoretical and experimental. For theoretical studies, which are based on electronic theory of alloys in pseudopotential approximation, Ti-Zr, Ti-Co and Ti-Cu alloys were chosen as the binary systems. Alloying element additions were performed to each binary for the investigation of the BGFA of multicomponent Ti-based alloys. Among the three studied binary systems, Ti-Cu was found to exhibit better BGFA, and Mn, Al and Ni elements were found to be suitable for improving the BGFA of Ti-Cu binary alloy system. BGFA of Ti-Cu binary and Ti-Cu-(Mn, Al, Ni) multicomponent alloys were investigated with the experimental studies that were carried out with performing arc melting and centrifugal casting operations. The characterizations of these alloys were done with scanning electron microscopy, X-ray diffraction analysis and differential scanning calorimetry. Ti60Cu35Mn5, Ti60Cu35Al5 and Ti60Cu35Ni5 alloys were produced and characterized as examples for ternary systems. Among them, Ti60Cu35Mn5 system was found to have better indications regarding to BGFA. Therefore, it was chosen as the main composition and multicomponent alloys of Ti59Cu35Mn5Al1, Ti59Cu35Mn5Ni1 and Ti58Cu35Mn5Al1Ni1 were synthesized and characterized.

This study is pertinent to setting a connection between glass forming ability (GFA) and topology of Fe-B based metallic glasses by combining intimate investigations on spatial atomic arrangements conducted via solid computer simulations with experimentations on high GFA bulk metallic glasses. In order to construct a theoretical framework, the nano-scale phase separation encountered in metallic glasses is investigated for amorphous Fe80B20 and Fe83B17 alloys via Monte Carlo equilibration and reverse Monte Carlo simulation. The phenomenon is identified regarding three topological aspects: 1) Pure Fe-clusters as large as ~0.9 nm and Fe-contours with ~0.72 nm thickness, 2) Fe-rich highly deformed body centered cubic regions, 3) B-centered prismatic units with polytetrahedral order forming distinct regions of high and low coordinations are found. All topological aspects are compiled into a new model called Two-Dimensional Projection Model for predicting contributions to short and medium range order (MRO) and corresponding spacing relations. The outcome geometrically involves proportions approximating golden ratio. After successfully producing soft magnetic Fe-Co-Nb-B-Si based bulk metallic glass and bulk nanocrystalline alloys with a totally conventional route, influences of alloying elements on structural units and crystallization modes are identified by the developed model and radial distributions. While Co atoms substitute for Fe atoms, Nb and Si atoms deform trigonal prismatic units to provide local compactions at the outset of MRO. Cu atoms alter the type of MRO which resembles crystalline counterparts and accompanying nanocrystals that precipitate. The GFA can be described by a new parameter quantifying the MRO compaction, cited as &amp / #934 / .

Amorphous metals have been discovered in 1960 and, because of their structures, exhibit very unique mechanical, magnetic and chemical properties that can have various applications. These properties qualify them as the potential material of the future. This work focuses on a new laser ablation technique to synthesize nanoparticles of amorphous metals from aqueous feedstock. One of the critical factors in the production of amorphous metal is the cooling rate used to synthesize them. The laser ablation of microparticle aerosol (LAMA) process used in this work, with a cooling rate estimated of 10¹² K/s, has all the characteristics required for the production of such metallic glasses. A Collison nebulizer is used to generate microdroplets of a nitrate solution containing the corresponding ratio of metals for the production of a Zr-Al-Ni based alloy. Once dried and conditioned, these microdroplets leave solid microparticles which are ablated by an excimer laser producing nanoparticles that are then filtered by virtual impaction. In order to characterize the nanoparticles obtained with this process nanoparticulate films produced by LAMA have been analyzed by optical profilometry, scanning electron microscopy (SEM) equipped with energy-dispersive x-ray spectroscopy (EDS) and transmission electron microscopy (TEM) equipped with EDS. The results agree with a hypothesis that the films contain oxidized, amorphous metal on the surface of the films. When the films are thin, they are fully oxidized, and simultaneous segregation of Zr occurs to the surface. The hypothesis and the results are discussed. / text

No description available.

The solid, liquid, and solidification properties of Pd, Ag pure metals and especially PdxAg1-x alloys are studied by using the molecular dynamics simulation. The effects of temperature and concentration on the physical properties of Pdx$Ag1-x are analyzed. Sutton-Chen (SC) and Quantum Sutton-Chen (Q-SC) many-body potentials are used as interatomic interactions which enable one to investigate the thermodynamic, static, and dynamical properties of transition metals. The simulation results such as cohesive energy, density, elastic constants, bulk modulus, pair distribution functions, melting points and phonon dispersion curves obtained for Pd, Ag and PdxAg1-x are in good agreement with the available experimental data at various temperatures. The predicted melting points of Pd, Ag and their binary alloys by using Q-SC potential parameters are closer to experimental values than the ones predicted from SC potential parameters. The liquid properties such as diffusion constants and viscosities computed from Q-SC potentials are also in good agreement with the available experimental data and theoretical calculations. Diffusion coefficients and viscosity results calculated from simulation obey the Arrhenius equation well. The coefficients of the Arrhenius equation are given in order to calculate the self-diffusion coefficient and shear viscosity of Pd-Ag alloys at the desired temperature and concentration. Using different cooling rates, we investigate glass formation tendency and crystallization of Pd-Ag metal alloys, by analyzing pair distribution function, enthalpy, volume, and diffusion coefficient. Pd-Ag alloys show the glass structure at fast cooling rates while it crystallizes at slow cooling rates. Glass and crystallization temperatures are also obtained from the Wendt-Abraham parameter. The split of the second peak in the pair distribution function is associated with the glass transition. Glass forming ability increases with increasing concentration of Ag in Pd-Ag alloys. Thermal and mechanical properties of Cu, Au metals and their ordered intermetallic alloys Cu3 Au(L12), CuAu(L10), and CuAu3(L12) are also studied to investigate the effects of temperature and concentration on the physical properties of Cu-Au alloys. The simulation results such as cohesive energy, lattice parameter, density, elastic constants, bulk modulus, heat capacity, thermal expansion, melting points, and phonon dispersion curves are in good agreement with the available experimental and theoretical data at various temperatures. The Q-SC potential parameters are more reliable in determining physical properties of metals and their random and ordered alloys studied in this work

In this study molecular dynamics simulation program in NVT ensemble using Velocity Verlet integration was written in order to investigate the glass forming ability of two metallic systems. The Zn-Mg system, one of the frontiers of simple metal-metal metallic glasses and Fe-B, inquiring attention due to presence of many bulk glass forming alloy systems evolved from this binary with different alloying element additions. In addition to this, atomistic calculations on the basis of ordering were carried out for both Zn-Mg and Fe-B systems. Ordering energy values are calculated using electronic theory of alloys in pseudopotential approximation and elements which increase the ordering energy between atoms were determined. The elements which increase the ordering energy most were selected as candidate elements in order to design bulk amorphous alloy systems. In the experimental branch of the study centrifugal casting experiments were done in order to see the validity of atomistic calculations. Industrial low grade ferroboron was used as the master alloy and pure element additions were performed in order to constitute selected compositions. Fe62B21Mo5W2Zr6 alloy was successfully vitrified in bulk form using nearly conventional centrifugal casting processing. Specimens produced were characterized using SEM, XRD, and DSC in order to detect the amorphous structure and also the crystalline counterpart of the structure when the cooling rate is lower. Sequential peritectic and eutectic reaction pattern was found to be important for metallic glasses which can be vitrified in bulk forms with nearly conventional solidification methods.