M.Tech. (Department of Chemistry, Faculty of Applied Sciences), Vaal University of Technology / Many oxidic iron compounds—iron oxides; oxy-hydroxides and hydroxides—not only play an important role in a variety of disciplines but also serve as a model system of reduction and catalytic reactions. There are more than 16 identifiable oxidic iron compounds. The reduction of these compounds has been investigated for centuries. Despite this, the reduction behavior of the oxides is not fully understood as yet. To date the reduction mechanism is still plagued with uncertainties and conflicting theories, partly due to the complex nature of these oxides and intermediates formed during the reduction. Thermodynamically, the reduction of iron oxide occurs in steps. For example, during the reduction of hematite (a-Fe2O3) magnetite (Fe3O4) is first formed followed by non-stoichiometric wüstite (Fe1-yO) and lastly metallic iron (a-Fe). The rate of transformation depends on the reduction conditions. Further, this reduction is accompanied by changes in the crystal structure. The reduction behavior of iron oxides using graphite under ball-milling conditions was investigated using Planetary mono mill (Fritsch Pulverisette 6), Mössbauer Spectroscopy (MS), X-ray Diffraction (XRD), Scanning electron microscopy (SEM) and Transmission Electron Microscopy (TEM). It was found that hematite transformed into magnetite, Wüstite and or cementite depending on the milling conditions. The study shows that by increasing the milling time, the rotational speed and / or the ball to powder ratio, the extent of the conversion of hematite to its reduction products increased. Further investigations are required for the elucidation of the reduction mechanism. The reaction og magnetite and graphite at different milling conditions lead to the formation of Fe2+ and Fe3+ species, the former increasing at the expense of Fe3O4. Fe3O4 completely disappeared after a BPR of 50:1 and beyond. The Fe2+ species was confirmed to be due to FeO using XRD analysis. HRSEM images Fe2O3 using scanning electron microscopy prior to and after milling at different times showed significant changes while the milling period was increased, HRSEM images showed that the once well defined hematite particles took ill-defined shapes and also became smaller in size, which was a results of the milling action that induced reaction between the two powders to form magnetite. EDX spectra at different milling times also confirmed formation of magnetite. EDX elemental analysis and quantification confirmed the elemental composition of starting material consisting mainly of iron. Similarly, HRSEM images of Fe3O4 using Scanning electron microscopy (SEM) prior to and after milling at different BPR showed significant changes when the milling period was increased. EDX spectra at different milling times also confirmed formation of partial FeO and EDX elemental analysis and quantification confirmed the elemental composition of starting material consisting mainly of iron than Fe2O3. TEM images of both Fe2O3 and Fe3O4 particles at different milling conditions displayed observable particle damages as a function of milling period.The once well - defined particles (Fe2O3 and Fe3O4 ) successively took ill – defined shapes, possibly accompanied by crystallite size reduction. MAS showed that the reactive milling of α- Fe2O3 and C resulted in reduction to Fe3O4 , FeO and or cementite depending on the milling conditions etc Time, milling speed and BPR variation which influenced the reduction. The study shows that by increasing the milling time, the rotational speed and / or the ball to powder ratio, the extent of the conversion of hematite to its reduction products increased. XRD study investigations even though were unable to detect spm species (Fe2+ and Fe3+ ) which has smaller crystallites below detection limits ,the variation in time showed an increment in the magnetite peaks accompanied by recession of hematite and graphite peaks as the milling time was increased which relates to the MAS observation.XRD also corroborated the data obtained from MAS that showed that the main constituent was magnetite and further evidence in support of the reduction of hematite to magnetite under reactive milling was obtained using XRD . Overall, the work demonstrated selective reduction of Fe2O3 to Fe3O4 and Fe3O4 to FeO by fine tuning the milling conditions. It is envisaged that the reduction of FeO to Fe and possible carburization to FexC could also be achieved.

Submitted by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2018-08-06T15:17:49Z No. of bitstreams: 1 DISSERTAÇÃO-Francisco Maciel de Brito Neto PPGCEM.pdf: 4657821 bytes, checksum: bfb975014ce10e6a646fdd1c54e9758b (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2018-08-06T15:18:13Z (GMT) No. of bitstreams: 1 DISSERTAÇÃO-Francisco Maciel de Brito Neto PPGCEM.pdf: 4657821 bytes, checksum: bfb975014ce10e6a646fdd1c54e9758b (MD5) / Made available in DSpace on 2018-08-06T15:18:13Z (GMT). No. of bitstreams: 1 DISSERTAÇÃO-Francisco Maciel de Brito Neto PPGCEM.pdf: 4657821 bytes, checksum: bfb975014ce10e6a646fdd1c54e9758b (MD5) Previous issue date: 2018-05-17 / CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico / Samples of samarium oxide (Sm2O3) and niobium oxide (Nb2O5) were submitted to Mechanical alloying technique and their structural evolution was accompanied by x-ray diffraction (XRD) measurements. In a few hours of milling SmNbO4 crystals were identified with two polymorphisms, one monoclinic and the other tetragonal. The diffractograms were simulated by Rietveld method and all crystallographic parameters were obtained, as well as the respective amounts of phases. The average crystallite sizes were estimated by the single-line method, indicating that both polymorphs have nanosized dimensions, that is, they are nanostructured. Combining calorimetric measurements, thermal treatments and x-ray diffraction the structural stability of the samples was studied. It was observed that the monoclinic structure undergoes phase transition to tetragonal structure in an exothermic process around 850 °C. The energy needed to promote the process was obtained by the Kissinger method and the XRD measurements indicate that the transition is irreversible. / Amostras de óxido de samário (Sm2O3) e óxido de nióbio (Nb2O5) foram submetidas à técnica moagem mecânica de alta energia e sua evolução estrutural foi acompanhada por medidas de difração de raios X (DRX). Em poucas horas de moagem foram identificados cristais de SmNbO4 com dois polimorfismos, um monoclínico e outro tetragonal. Os difratogramas foram simulados por método de Rietveld e todos os parâmetros cristalográficos foram obtidos, assim como as respectivas quantidades de fases. Os tamanhos médios de cristalitos foram estimados pelo método da linha única (single-line) indicando que ambos polimorfos possuem dimensões nanométricas, ou seja, são nanoestruturados. Combinando medidas calorimétricas, tratamentos térmicos e difração de raios x a estabilidade estrutural das amostras foi estudada. Foi observado que a estrutura monoclínica sofre transição de fase para estrutura tetragonal em um processo exotérmico em torno de 850°C. A energia necessária para promover o processo foi obtida pelo método de Kissinger e as medidas de DRX indicam que a transição é irreversível.

Lors de la synthèse des aciers ODS, la première étape consiste à réaliser un broyage actif, appelé mécano-synthèse, entre les matériaux de départ qui sont la poudre métallique et les renforts d’oxyde. Ce procédé peut se réaliser au moyen d’un broyeur à boulets, constitué d’une cuve cylindrique à l’intérieur de laquelle des billes en acier sont introduites. Le broyage résulte des combinaisons de chocs entre billes, poudre et paroi de la cuve, ce qui conduit à une évolution de la de la taille, de leur forme et de leur polydispersité. La première partie de cette thèse s’est attachée à élaborer un moyen de caractérisation de la poudre par des mesures ultrasonores. Une méthode qui consiste à sonder un échantillon de poudre métallique pour la mesure des paramètres acoustiques s’est avérée être adaptée pour la qualification de la poudre métallique en cours de broyage. Une dépendance des paramètres acoustiques avec les caractéristiques morphologiques du milieu a également été mise en évidence pour des échantillons granulaires. Dans une deuxième partie, l’optimisation du procédé par l’identification de la vitesse optimale de rotation de la cuve est recherchée dans un premier temps. Une mise en parallèle des signaux acoustiques et vibratoires en fonction de la vitesse de rotation de la cuve avec le mouvement des billes, montre que les énergies acoustique et vibratoire sont des indicateurs pouvant conduire à la vitesse de rotation optimale. Puis, il est montré comment des mesures acoustiques et vibratoires durant un broyage permettent de caractériser l’évolution de la nature des poudres et d’identifier la présence de colmatage de la poudre sur les parois de la cuve. / During the ODS steel (Oxide Dispersion Strengthened) synthesis, the first stage consists in an active milling between original materials, which are metallic powder and oxide to obtain reinforced micro/nanoscale dispersions. This process, known as mechanical alloying, could be realized by balls milling composed by a cylindrical tank rotating around its main axis, within which steel beads are introduced. The grinding results from different combinations of collisions between beads and powders on the tank walls, that lead to morphological grain powder evolution (grain size and shape). The first part of this thesis proposes an ultrasonic method to characterize the metallic powder. An experimental method, which consists in acoustic probing for measuring linear acoustic parameters (longitudinal wave velocity and elastic modulus) of a slab of powder sample, appears to be suitable to follow different mechanical alloying stages. A dependence of the acoustic parameters on the morphological characteristics of metallic powder (grain shape and grain size distribution) is shown with the same sample preparation and the same confining pressure. In the second part, optimization process by identification of ball milling optimal rotation speed is researched in a first step. Correlation between acoustic or vibration signals and bead motion versus rotation speed, shows that acoustic and vibration energy are good indicators that can be used to find the optimal rotation speed. In a second step, acoustic and vibration measures are used to follow grain material properties evolution during a grinding (for a period of 176hrs) and to identify powder clogging mechanism on a milling tank.

This thesis deals with the influence of process parameters on the contamination level of powder materials produced by mechanical alloying (MA) technology. For this purpose austenitic stainless steel 316 L and equiatomic CoCrFeNi high-entropy alloy (HEA) were prepared by high-energy ball milling. Both materials were milled in argon and nitrogen atmospheres from 5 to 30 hours. Spark plasma sintering method (SPS) was then used for consolidation of chosen powder samples. Chemical analysis of contamination within MA was carried out using combustion analysers for determination of carbon, oxygen, and nitrogen contents after different lengths of milling. Also differences in chemical composition of powder and corresponding bulk samples were measured. The microstructure analysis using scanning electron microscopy (SEM) of both powder and bulk materials was executed with focus on oxide and carbide presence and dispersion. Increasing content of carbon with increasing milling time was observed across all measured samples. This contamination is attributed to using milling vial made of tool steel AISI D2 (containing 1,55 wt. % of carbon). Increase of carbon content within consolidation using SPS was also observed. Milling of specimens using N2 as milling atmosphere caused higher contamination level in both AISI 316 L and HEA compared to milling in argon.

High Entropy Alloy (HEA) is a class of construction steels based on the mixing of five or more elements in approximately equimolar ratios. Despite the ambiguity of their future use, HEAs represent a significantly new group of construction materials that are currently receiving a great deal of attention. Single-phase HEAs fail when used at elevated tempera-tures. The improvement of their high-temperature resistance was achieved by introducing a dispersion of oxides Al2O3 and Y2O3. To generalize the positive effect of dispersions on the mechanical properties at elevated temperatures, particles of a similar nature were cho-sen. These were dispersed particles of nitrides: hardness-incompatible AlN and hardness-compatible BN. The particles were evenly distributed inside the alloys by mechanical al-loying and compacted by SPS (Spark Plasma Sintering). The new structural alloy reached a density higher than 96.5 % and brought an increase in yield strength at room tempera-ture of up to 67 % and 40 % at elevated temperatures, while maintaining a homogeneous distribution of input powders.

Vývoj nových materiálů pro součásti v moderních technologiích vystavené extrémním podmínkám má v současné době rostoucí význam. Děje se tak v důsledku neustále se zvyšujících požadavků průmyslových odvětví na lepší konstrukční vlastnosti nosných materiálů. Ve světle těchto faktů si tato studie klade za cíl posoudit nové složení slitin s vysokou entropií, které se vyznačují vysokým aplikačním potenciálem pro kritické aplikace. Slitiny jsou připravovány práškovou metalurgií, t.j. kombinací mechanického legování a slinování v pevné fázi. Pro účely srovnávaní vlastností jsou vybrané kompozice vyrobeny také tradičními metalurgickými metodami v roztaveném stavu, jako je vakuové indukční tavení a následné lití nebo vakuové obloukové tavení. Prášková metalurgie umožňuje postupný vývoj kompozitů s kovovou matricí (MMC) prostřednictvím přípravy oxidicky zpevněných HEA slitin. To je možné díky inherentním in-situ reakcím během procesu výroby. Když se naopak zvolí výrobní postup z taveniny, připravený kovový materiál vykazuje velké rozdíly v mikrostrukturách a souvisejících vlastnostech, v porovnání se stejným materiálem vyrobeným práškovou cestou (PM). Vyrobené práškové a tavené materiály jsou detailně charakterizovány s ohledem na komplexní vyhodnocení vlivu různých metod zpracování. Práce se zejména orientuje na mikrostrukturní charakteristiky materiálů a jejich mechanické vlastnosti, včetně vlivu tepelného zpracování na fázové transformaci a mikrostrukturní stabilitu připravených materiálů.

In this thesis, novel bulk Al-based alloys with high content of Al have been produced by powder metallurgy methods from amorphous and partially amorphous materials. Different processing routes, i.e. mechanical alloying of elemental powder mixtures, controlled pulverization of melt-spun glassy ribbons and gas atomization, have been employed for the production of the Al-based powders. Among the different processing routes, gas atomization is the best choice for the production of Al-based amorphous and partially amorphous powders as precursors for the subsequent consolidation step because it allows the production of large quantities of powders with homogeneous properties (e.g. structure and thermal stability) along with a uniform size distribution of particles. Amorphous and nanocrystalline powders have to be consolidated to achieve dense bulk specimens. However, consolidation of these phases is not an easy task and special care has to be taken with respect to accurate control of the consolidation parameters in order to achieve dense bulk specimens without inducing undesirable microstructural transformations (e.g. crystallization and grain coarsening) or insufficient particle bonding. Consequently, the effect of temperature on viscosity as well as on phase formation has been studied in detail in order to select the proper consolidation parameters. Following their characterization, the Al-based powders have been consolidated into bulk specimens by hot pressing (HP), hot extrusion and spark plasma sintering (SPS) and their microstructure and mechanical properties have been extensively investigated. Consolidation into highly-dense bulk samples cannot be achieved without extended crystallization of the glassy precursors. Nevertheless, partial or full crystallization during consolidation leads to remarkable mechanical properties. For example, HP Al84Gd6Ni7Co3 samples display a remarkably high strength of about 1500 MPa, which is three times larger than the conventional high-strength Al-based alloys, along with a limited but distinct plastic deformability (3.5 – 4%). Lower strength (930 MPa) but remarkably larger plastic strain exceeding 25 % has been achieved for the Al87Ni8La5 gas-atomized powders consolidated by SPS above their crystallization temperature. Similarly, HP Al90.4Y4.4Ni4.3Co0.9 bulk samples display high compression strength ranging between 820 and 925 MPa combined with plastic strain in the range 14 – 30%. Finally, preliminary tensile tests for the Al90.4Y4.3Ni4.4Co0.9 alloy reveal promising tensile properties comparable to commercial high-strength Al-based alloys. The mechanical behavior of the consolidated specimens is strictly linked with their microstructure. High strength and reduced plasticity are observed when a residual amorphous phase is present. On the other hand, reduced strength but enhanced plastic deformation is a result of the complete crystallization of the glass and of the formation of a partially or fully interconnected network of deformable fcc Al. These results indicate that the combined devitrification and consolidation of glassy precursors is a particularly suitable method for the production of Al-based materials characterized by high strength combined with considerable plastic strain. Through this method, the mechanical properties of the consolidated samples can be varied within a wide range of strength and ductility depending on the microstructure and the consolidation techniques used. This might open a new route for the development of innovative high-performance Al-based materials for transport applications.

科学研究費補助金 研究種目:基盤研究(B)(2) 課題番号:11555183 研究代表者:金武 直幸 研究期間:1999-2001年度

[ES] Las aleaciones biomédicas de alta entropía (Bio-HEA) con propiedades no tóxicas, sintetizadas mediante métodos de pulvimetalurgia, han recibido una atención limitada a pesar de su potencial para un rendimiento mecánico y biológico favorable. Este estudio tuvo como objetivo investigar sistemáticamente las características microestructurales, mecánicas, electroquímicas y de liberación de iones de distintas composiciones de aleaciones porosas organizadas en tres grupos. El grupo uno consta de cuatro aleaciones porosas de TNZT EB con distintas proporciones de Ti/Ta, mientras que el grupo dos consta de dos aleaciones porosas de TNZTM EB con diferentes proporciones de Ti/Mo. Por último, el grupo tres incluye dos aleaciones más densas de TNZT SPS con diferentes proporciones de Ti/Ta. En el análisis de la microestructura de las aleaciones TNZT EB, es evidente la presencia de fase (matriz) BCC semiequiaxial y micrométrica con un pequeño contenido de fase HCP. Propiedades mecánicas, que abarcan módulos elásticos (83-100 GPa), dureza (373-430 HVN), flexión máxima (225-476 MPa), resistencia a la tracción (120-256 MPa) y compresión (713-1410 MPa); además, la velocidad de corrosión electroquímica (4,5-9,6 ¿m año-1) y la liberación de iones (toxicidad, 0,04-1,1 ¿m año-1), se encuentran dentro de los límites aceptables para los biomateriales de implantes. Sorprendentemente, aumentar el contenido de Ti (y disminuir Ta) muestra ventajas en la mejora de la resistencia mecánica y reduce el módulo elástico. La microestructura del grupo dos, específicamente las aleaciones Ti20 EB TNZTM, exhibe fases (matriz) BCC semiequiaxiales y micrométricas con proporciones disminuidas de fases Zr FCC y HCP. Por el contrario, en Ti25 EB TNZTM, la microestructura comprende fases FCC (matriz) micrométricas y semiequiaxiales con cantidades reducidas de fases HCP y BCC. Es digno de mención subrayar el desafío de la débil homogeneidad que conduce a una heterogeneidad evidente en las aleaciones TNZTM EB. Las propiedades mecánicas, incluidos módulos elásticos (78-80 GPa), dureza (257-294 HVN), flexión máxima (186-210 MPa), resistencia a la tracción (121-144 MPa), compresión (661-774 MPa), corrosión electroquímica. (5-6,6 ¿m año-1) y la liberación de iones (toxicidad, 0,3-0,8 ¿m año-1) están también dentro de rangos aceptables para biomateriales de implantes. La reducción ventajosa del módulo elástico y la liberación de iones se logra disminuyendo el contenido de Ti (y aumentando el Mo), mientras que la mejora del fortalecimiento mecánico se facilita al aumentar el contenido de Ti (y disminuyendo el Mo). El grupo tres, aleaciones TNZT SPS, exhibe una microestructura con fases BCC (matriz) micrométricas y semiequiaxiales y un menor contenido de fases HCP y FCC. Los módulos elásticos (85-88 GPa), dureza (268-349 HVN), flexión máxima (225-476 MPa) y corrosión electroquímica (4,7-5,1 ¿m año-1) resultan ligeramente inferiores que en las aleaciones de polvos elementales. El aumento del contenido de Ti (y la disminución de Ta) muestran ventajas en cuanto a la reducción del módulo elástico y mejoran la dureza. El valor moderado del módulo elástico tiene beneficios potenciales para aliviar el efecto de apantallamiento de tensiones entre los implantes y el tejido orgánico. Sin embargo, en el caso del grupo uno (TNZT EB), la velocidad de corrosión mostró una tendencia ascendente, mientras que la liberación de iones metálicos disminuyó con el aumento del contenido de Ti. Por el contrario, para el grupo dos (TNZTM EB), tanto la velocidad de corrosión como la liberación de iones metálicos disminuyeron en respuesta al aumento del contenido de Ti. Dentro del grupo tres (TNZT SPS) hubo un aumento en la velocidad de corrosión a medida que aumentaba el contenido de Ti. Con base en lo anterior, las aleaciones porosas de TNZT EB con contenidos de Ti medios y altos (Ti30 EB y Ti35 EB) resultan los candidatos más prometedores para aplicaciones de implantes biomédicos. / [CA] Els aliatges biomèdics d'alta entropia (Bio-HEA) amb propietats no tòxiques, sintetitzats mitjançant mètodes de pulvimetal·lúrgia, han rebut una atenció limitada malgrat el seu potencial per a un rendiment mecànic i biològic favorable. Aquest estudi te com a objectiu investigar sistemàticament les característiques microestructurals, mecàniques, electroquímiques i d'alliberament d'ions de diferents composicions d'aliatges porosos organitzats en tres grups. El grup u consta de quatre aliatges porosos de TNZT EB amb diferents proporcions de Ti/Ta, mentre que el grup dos consta de dos aliatges porosos de TNZTM EB amb diferents proporcions de Ti/Mo. Finalment, el grup tres inclou dos aliatges més denses de TNZT SPS amb diferents proporcions de Ti/Ta. A l'anàlisi de la microestructura dels aliatges TNZT EB, és evident la presència de fase (matriu) BCC semiequiaxial i micromètrica amb un petit contingut de fase HCP. Propietats mecàniques, que abasten mòduls elàstics (83-100 GPa), duresa (373-430 HVN), flexió màxima (225-476 MPa), resistència a la tracció (120-256 MPa) i compressió (713-1410 MPa); a més, la velocitat de corrosió electroquímica (4.5-9.6 ¿m any-1) i l'alliberament d'ions (toxicitat, 0.04-1.1 ¿m any-1), es troben dins dels límits acceptables per als biomaterials d'implants. Sorprenentment, augmentar el contingut de Ti (i disminuir Ta) mostra avantatges en la millora de la resistència mecànica i redueix el mòdul elàstic. La microestructura del grup dos, específicament els aliatges Ti20 EB TNZTM, exhibeix fases (matriu) BCC semiequiaxials i micromètriques amb proporcions disminuïdes de fases Zr FCC i HCP. Per contra, a Ti25 EB TNZTM, la microestructura comprèn fases FCC (matriu) micromètriques i semiequiaxials amb quantitats reduïdes de fases HCP i BCC. És digne de menció subratllar el desafiament de la feble homogeneïtat que condueix a una heterogeneïtat química evident en els aliatges TNZTM EB. Les propietats mecàniques, inclosos mòduls elàstics (78-80 GPa), duresa (257-294 HVN), flexió màxima (186-210 MPa), resistència a la tracció (121-144 MPa), compressió (661-774 MPa), corrosió electroquímica. (5-6.6 ¿m any-1) i l'alliberament d'ions (toxicitat, 0,3-0,8 ¿m any-1) estan també dins de rangs acceptables per a biomaterials d'implants. La reducció avantatjosa del mòdul elàstic i l'alliberament d'ions s'aconsegueix disminuint el contingut de Ti (i augmentant el Mo), mentre que la millora de l'enfortiment mecànic es facilita en augmentar el contingut de Ti (i disminuint el Mo). El grup tres, aliatges TNZT SPS, exhibeix una microestructura amb fases BCC (matriu) micromètriques i semiequiaxials i un menor contingut de fases HCP i FCC. Els mòduls elàstics (85-88 GPa), duresa (268-349 HVN), flexió màxima (225-476 MPa) i corrosió electroquímica (4.7-5.1 ¿m any-1) resulten lleugerament inferiors que en els aliatges de pols elementals. L'augment del contingut de Ti (i la disminució de Ta) mostren avantatges quant a la reducció del mòdul elàstic i milloren la duresa. El valor moderat del mòdul elàstic té beneficis potencials per alleujar l'efecte d'apantallament de tensions entre els implants i el teixit orgànic. Tot i això, en el cas del grup u (TNZT EB), la velocitat de corrosió va mostrar una tendència ascendent, mentre que l'alliberament d'ions metàl·lics va disminuir amb l'augment del contingut de Ti. Per contra, per al grup dos (TNZTM EB), tant la velocitat de corrosió com l'alliberament d'ions metàl·lics van disminuir en resposta a l'augment del contingut de Ti. Dins el grup tres (TNZT SPS) hi va haver un augment en la velocitat de corrosió a mesura que augmentava el contingut de Ti. Amb base a això, els aliatges porosos de TNZT EB amb continguts de Ti mitjans i alts (Ti30 EB i Ti35 EB) resulten els candidats més prometedors per a aplicacions d'implants biomèdics. / [EN] Biomedical high entropy alloys (Bio-HEAs) with non-toxic properties, synthesized through powder metallurgy methods, have received limited attention despite their potential for favorable mechanical and biological performance. This study aimed to systematically investigate the microstructural, mechanical, electrochemical, and ion release features of distinct porous alloy compositions organized into three groups. Group one consisted of four porous TNZT EB alloys with varied Ti/Ta ratios, while group two comprised two porous TNZTM EB alloys with different Ti/Mo ratios. Lastly, group three included two porous TNZT SPS alloys with varying Ti/Ta ratios. In the microstructure analysis of TNZT EB alloys, the presence of semi-equiaxed and micrometric BCC phases (matrix) with lower HCP phase content was evident. Mechanical properties, encompassing elastic moduli (83-100 GPa), hardness (373-430 HVN), ultimate bending (225-476 MPa), tensile (120-256 MPa) strength, and compression (713-1410 MPa), in addition to electrochemical corrosion (4.5-9.6 ¿m year-1) and ion release (toxicity, 0.04-1.1 ¿m year-1), fell within acceptable limits for implant biomaterials. Remarkably, augmenting the Ti content (and decreasing Ta) exhibited advantages in improving mechanical strength and reducing the elastic modulus. The microstructure of group two, specifically the Ti20 EB TNZTM alloys, exhibited semi-equiaxed and micrometric BCC phases (matrix) with diminished proportions of FCC and HCP phases. Conversely, in Ti25 EB TNZTM, the microstructure comprised semi-equiaxed and micrometric FCC-phases (matrix) with reduced quantities of HCP and BCC phases. It is noteworthy to underscore the challenge of weak homogeneity leading to evident heterogeneity in TNZTM EB alloys. The mechanical properties, including elastic moduli (78-80 GPa), hardness (257-294 HVN), ultimate bending (186-210 MPa), tensile (121-144 MPa) strength, compression (661-774 MPa), electrochemical corrosion (5-6.6 ¿m year-1), and ion release (toxicity, 0.3-0.8 ¿m year-1), fell within acceptable ranges for implant biomaterials. The advantageous reduction of elastic modulus and ion releases was achieved by decreasing the Ti content (and increasing Mo), whereas enhancing mechanical strengthening was facilitated by increasing the Ti content (and decreasing Mo). Group three, TNZT SPS alloys, exhibited a microstructure with semi-equiaxed and micrometric BCC-phases (matrix) and lower HCP and FCC phase content. The elastic moduli (85-88 GPa), hardness (268-349 HVN), and ultimate bending (225-476 MPa), and electrochemical corrosion (4.7-5.1 ¿m year-1). Increasing Ti content (and decreasing Ta) were advantageous for reducing the elastic modulus and improving hardness. The moderate elastic modulus value holds potential benefits in alleviating the mechanical incongruence between the implant and organic tissue. Nevertheless, in the case of group one (TNZT EB), the corrosion rate exhibited an upward trend, while the metallic ion release declined with increasing Ti content. In contrast, for group two (TNZTM EB), both the corrosion rate and metallic ion release diminished in response to escalating Ti content. Within group three (TNZT SPS) there was increase in the corrosion rate as the Ti content escalated. Based on the above, porous TNZT EB alloys with medium and highest Ti contents (Ti30 EB and Ti35 EB) emerged as promising candidates for biomedical implant applications / Kamel Mohammad Al-Hawajreh, G. (2024). Performance Effect of the Content of Alloying Elements in the Development of High Entropy Alloys of the Ti-Nb-Zr-Ta-Mo Family for Biomedical Applications [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/208235