المؤلفون: López Jiménez, Isabel

المساهمون: University/Department: Universitat de Barcelona. Departament de Ciència dels Materials i Química Física

مرشدي الرسالة: Llorca i Isern, Núria

المصدر: TDX (Tesis Doctorals en Xarxa)

مصطلحات موضوعية: Pulvimetal·lúrgia, Pulvimetalurgia, Powder metallurgy, Aliatges, Aleaciones, Alloys, Entropia, Entropía, Entropy, Microscòpia electrònica, Microscopia electrónica, Electron microscopy, Ciències Experimentals i Matemàtiques

الوصف: Programa de Doctorat en Enginyeria i Ciències Aplicades

الوصف (مترجم): [spa] Durante los últimos años el estudio de las aleaciones de alta entropía, o high entropy alloys (HEA), ha sido un tema en auge. Las HEA presentan de cinco a más elementos en proporción equimolar y una microestructura de solución sólida. Aunque, la comunidad científica no ha llegado a una definición clara de cuáles son los criterios que deben cumplir estas aleaciones. Las aleaciones HEA presentan propiedades excelentes y sus óptimas características las están haciendo muy interesantes para aplicaciones estructurales en la industria aeronáutica, en aplicaciones relacionadas con la energía y en la industria química de la catálisis, entre otras. Gracias a la aleación mecánica (MA) es posible obtener soluciones sólidas de sistemas termodinámicamente inmiscibles y materiales nanoestructurados. Este método se ha empleado durante años para la producción de multitud de materiales y piezas de pulvimetalúrgia. Esta tesis doctoral plantea la síntesis de tres aleaciones HEA donde la proporción de los elementos no es equiatómica. Los elementos han sido Fe, Al, Ni, Cu y Co en diferentes proporciones. Las aleaciones convencionales de estos elementos muestran de por si propiedades sobresalientes y gran variedad de aplicaciones. La síntesis de la aleación FeAlNiCuCo pretende contribuir al debate de la obtención de una HEA con solución sólida, a pesar de que su proporción de elementos no sea equimolar. En el trabajo se plantea encontrar las condiciones óptimas de síntesis de estas nuevas aleaciones mediante MA y estudiar sus propiedades. Esta investigación parte de una primera etapa de búsqueda y evaluación de los parámetros que las hacen únicas. Se realiza un estudio bibliográfico de los indicadores termodinámicos que debe cumplir una HEA. También se evalúan las diferentes técnicas de síntesis utilizadas actualmente, considerando las ventajas y desventajas que presentan. La primera etapa de estudio bibliográfico ha permitido obtener toda la información necesaria para plantear un diseño de la aleación FeAlNiCuCo que cumpla con todos los parámetros termodinámicos fijados para la obtención de una solución sólida. Seguidamente, se ha decidido una síntesis con aleación mecánica. A continuación, se efectúa la síntesis de la aleación HEA y se optimizan las condiciones para la obtención de una solución sólida. Una segunda etapa de caracterización de las aleaciones ha permitido un estudio en profundidad de las aleaciones. Las técnicas de caracterización de microscopía electrónica de barrido (FESEM-EDS), difracción de rayos X (DRX) y espectroscopia Mössbauer juegan un papel clave en la determinación de la microestructura y la red cristalina de las HEAs. A su vez, permiten evaluar los cambios de la muestra durante varios puntos del procesado, como son la síntesis mecánica y la sinterización a diferentes temperaturas. Otras técnicas como XPS, picnometría de helio o la calorimetría diferencial de barrido (DSC) también han aportado datos fundamentales para la interpretación de los resultados. Igualmente se han estudiado propiedades físico-químicas de las tres aleaciones. Los análisis se han centrado en la variación de la microestructura de las muestras a diferentes temperaturas, su área superficial BET y su porosidad, su comportamiento magnético, su resistencia a la corrosión y su microdureza. En último lugar, con todos los datos reunidos, se han evaluado en conjunto las tres aleaciones FeAlNiCuCo obtenidas. Se han valorado las diferencias y similitudes entre ellas y se ha considerado cuál presenta las mejores propiedades y estabilidad. De igual manera, se ha determinado que la microestructura para las tres aleaciones es de solución sólida, a pesar de que no presentan una proporción equiatómica como alguna definición de las aleaciones de alta entropía requiere. La ruta de síntesis de aleación mecánica se ha validado como adecuada para esta obtención y se ha planteado las posibles aplicaciones de las aleaciones HEA.
[eng] In recent years, the study of high entropy alloys (HEAs) has been a hot topic. HEAs have from five to more elements in equimolar proportion and a solid solution microstructure. Although, the scientific community has not agreed in a clear definition of what are the criteria that these alloys must fulfill. HEA alloys exhibit excellent properties, and their optimal characteristics are highly interesting for a wide range of applications. This doctoral thesis raises the synthesis of three HEA alloys where the proportion of the elements is not equimolar. The elements chosen have been the Fe, Al, Ni, Cu and Co in different proportions. The synthesis of the alloy FeAlNiCuCo aims to contribute to the debate of obtaining a HEA with solid solution, although its proportion of elements is not equimolar. The work claims to find the optimal conditions of synthesis of these new alloys by mechanical alloying and study their physicochemical properties. The bibliographic study has allowed to obtain all the necessary information to propose a design of the alloys FeAlNiCuCo that accomplish all the thermodynamic parameters set to obtain a solid solution. A second stage of characterization has allowed a depth study of the alloys. Scanning electron microscopy (FESEM-EDS), X-ray diffraction (XRD) and Mössbauer spectroscopy characterization techniques play a key role in establishing the microstructure and the crystal lattice of the HEAs. Other techniques such as XPS, helium pycnometry or differential scanning calorimetry (DSC) have also provided fundamental data for the interpretation of the results. Physicochemical properties of the three alloys have also been studied. Finally, with all the data collected, the three FeAlNiCuCo alloys obtained have been evaluated. The differences and similarities between them have been assessed and which one has the best properties and stability has been considered. Furthermore, it has been determined that the microstructure for the three alloys is solid solution, although they do not present an equimolar proportion as the definition of HEA requires. The synthesis route of mechanical alloying has been optimized and validated as suitable for this obtaining and some of the possible applications of HEA alloys has raised.

وصف الملف: application/pdf

الوصول الحر: http://hdl.handle.net/10803/688215Test

المؤلفون: Yang, Xin¹ (AUTHOR) yangxin15680824707@163.com, Li, Kaihua^1,2,3 (AUTHOR) lkh002@163.com, Li, Jun¹ (AUTHOR) lkh002@163.com, Sheng, Zhuo^2,3,4 (AUTHOR), Liu, Ying¹ (AUTHOR)

المصدر: Materials (1996-1944). Jun2024, Vol. 17 Issue 12, p2904. 16p.

مصطلحات موضوعية: *TITANIUM, *POWDER metallurgy, *TITANIUM alloys, *LOW temperatures, *MAGNESIUM alloys, *POROSITY, *MAGNESIUM

مستخلص: In this work, the preparation of titanium sponge by magnesium thermal method is regarded as the liquid-phase sintering process of titanium, and powder-metallurgy sintering technology is utilized to simulate the aggregation–growth and densification behavior of titanium particles in a high-temperature liquid medium (the molten Mg-MgCl2 system). It was found that compared with MgCl2, Mg has better high-temperature wettability and reduction effect, which promotes titanium particles to form a sponge titanium skeleton at lower temperature. The aggregation degree of titanium particles and the densification degree of a sponge titanium skeleton can be improved by increasing the temperature and the relative content of Mg in the melting medium. The kinetics study shows that with the increase in temperature, the porosity of the titanium particle aggregates and the sponge titanium skeleton decreases, and their density growth rate increases. With the extension of time, the aggregation degree of titanium particles and the densification degree of sponge titanium gradually increase. This work provides a theoretical reference for controlling the density of titanium sponge in industry. [ABSTRACT FROM AUTHOR]

المؤلفون: Marczewski, M.^1,2,3 (AUTHOR) mateusz.marczewski@pit.lukasiewicz.gov.pl, Wieczerzak, K.⁴ (AUTHOR), Maeder, X.⁴ (AUTHOR), Lapeyre, L.^1,4 (AUTHOR), Hain, C.^1,4 (AUTHOR), Jurczyk, M.⁵ (AUTHOR), Nelis, T.^1,4 (AUTHOR)

المصدر: Journal of Materials Science. May2024, Vol. 59 Issue 20, p9107-9125. 19p.

مصطلحات موضوعية: *MAGNETRON sputtering, *POWDER metallurgy, *MECHANICAL alloying, *MANUFACTURING processes, *YOUNG'S modulus, *MICROSTRUCTURE

مستخلص: At the interface of thin film development and powder metallurgy technologies, this study aims to characterise the mechanical properties, lattice constants and phase formation of Ti-Nb alloys (8–30 at.%) produced by different manufacturing methods, including conventional powder metallurgy (PM), mechanical alloying (MA) and high power impulse magnetron sputtering (HiPIMS). A central aspect of this research was to investigate the different energy states achievable by each synthesis method. The findings revealed that as the Nb content increased, both the hardness and Young's modulus of the PM samples decreased (from 4 to 1.5 and 125 to 85 GPa, respectively). For the MA alloys, the hardness and Young's modulus varied between 3.2 and 3.9 and 100 to 116 GPa, respectively, with the lowest values recorded for 20% Nb (3.2 and 96 GPa). The Young's modulus of the HiPIMS thin film samples did not follow a specific trend and varied between 110 and 138 GPa. However, an increase in hardness (from 3.6 to 4.8 GPa) coincided with an increase in the β2 phase contribution for films with the same chemical composition (23 at.% of Nb). This study highlights the potential of using HiPIMS gradient films for high throughput analysis for PM and MA techniques. This discovery is important as it provides a way to reduce the development time for complex alloy systems in biomaterials as well as other areas of materials engineering. [ABSTRACT FROM AUTHOR]

المؤلفون: Uthirapathy, C.¹ (AUTHOR) vijaymech51@gmail.com, Haresh, C. P.¹ (AUTHOR), Vaiikunth, B.¹ (AUTHOR), Ukesh, R.¹ (AUTHOR), Saran, S.¹ (AUTHOR)

المصدر: AIP Conference Proceedings. 2024, Vol. 2853 Issue 1, p1-12. 12p.

مصطلحات موضوعية: *MAGNESIUM compounds, *POWDER metallurgy, *TITANIUM, *BONE marrow, *HYDRAULIC presses, *BIODEGRADABLE plastics, *BIODEGRADABLE materials

مستخلص: Bone marrow implantation had occurred with the assistance of titanium-based materials, however it includes specific hindrances inside the human body. To survive this significant disadvantage, researchers inferred that magnesium can be supplanted by the titanium yet it has too its disadvantages to compare that magnesium-based compounds can be utilized, yet there is a ton and loads of Mg-based amalgams can be shaped. Magnesium and magnesium-based compounds are in the spotlight for biomedical applications. Furthermore, a considerable lot of the beneficial things are seen over biodegradable polymers, ceramics and conventional metallic materials. Materials what's more, strategies: Magnesium, calcium, zinc, aluminum and manganese are the materials taken for the composite. Additionally, materials are gone through for ball milling processing, Hydraulic powered press and afterward materials had gone through for cylindrical heaters with argon - cleansing test and cold vacuum. After that it has gone for pressure test. Results: The acquired outcomes for Mg-Zn-Al-Ca, Mg-Zn-Ca-Mn (1) and Mg-Zn-Ca-Mn (2) is Fmax= 7.85 KN, 3.964 KN and 5.48 KN separately. End: To manufacture and break down the composite of magnesium, zinc, calcium, aluminum furthermore, manganese, powder metallurgy strategy is utilized at various sintering temperatures. It is testing yet still it is promising primarily getting these new sorts of biodegradable metallic gadgets/inserts. [ABSTRACT FROM AUTHOR]

المؤلفون: Wen, Guoyuan¹ (AUTHOR), Li, Zhuan¹ (AUTHOR) lizhuan@csu.edu.cn, Wu, Jiaqi¹ (AUTHOR), Gao, Zonglong¹ (AUTHOR), Li, Ye¹ (AUTHOR), Zhou, Hao¹ (AUTHOR)

المصدر: Ceramics International. Sep2024:Part B, Vol. 50 Issue 17, p30763-30775. 13p.

مصطلحات موضوعية: *POWDER metallurgy, *FRICTION, *FERRIC oxide, *MACHINE learning, *METALLIC films, *FRETTING corrosion

مستخلص: By incorporating the dual ceramic elements TiB 2 /B 4 C, we investigated their impact on the mechanical properties, thermal properties, and friction performance of copper-based powder metallurgy materials, and elucidated the friction wear mechanism. Additionally, machine learning algorithms were employed to predict the friction coefficient and stability coefficient. The conclusions are as follows:With the increase in the TiB 2 /B 4 C ratio, the trend of mechanical properties initially increases and then decreases, with the optimum ratio being 5:3 for TiB 2 and B 4 C, exhibiting superior mechanical properties. Moreover, B 4 C enhances the thermal conductivity of copper-based friction materials more effectively than TiB 2. In terms of overall friction performance, the ratio of TiB 2 to B 4 C at 5:3 yields better frictional properties. The primary components of the friction surface friction film are CuO, Cu 2 O, Fe 2 O 3 , and B 2 O 3 , transitioning from a ceramic film to a metallic film as the TiB 2 /B 4 C ratio increases. The friction wear mechanism shifts from abrasive wear to severe fatigue wear as the TiB 2 /B 4 C ratio increases, accompanied by oxidative wear. Furthermore, an AdaBoost algorithm model was developed to effectively predict the friction coefficient and stability coefficient, with accuracies of 0.9993 and 0.8739, respectively. [ABSTRACT FROM AUTHOR]

المؤلفون: Kamei, Shuhei^1,2 (AUTHOR), Hirayama, Tomoko¹ (AUTHOR) tomoko@me.kyoto-u.ac.jp, Somekawa, Hidetoshi^1,2 (AUTHOR) SOMEKAWA.Hidetoshi@nims.go.jp, Matsuoka, Takashi¹ (AUTHOR)

المصدر: Ceramics International. Sep2024:Part A, Vol. 50 Issue 17, p30359-30366. 8p.

مصطلحات موضوعية: *MECHANICAL wear, *POWDER metallurgy, *WEAR resistance, *EXTRUSION process, *FRICTION

مستخلص: The tribological properties are evaluated using several types of Mg/SiC composites, which SiC powders with particle sizes of 20∼30 nm, 130 nm and 2∼3 μm are dispersed in up to 25 % by volume fraction. Sound and bulky Mg/SiC composites are successfully fabricated by powder-metallurgy combining extrusion process. The initial SiC particle size and their dispersed volume fraction affect the wear and friction properties. The specific wear rate increases with increasing contents of SiC particles, regardless of the initial SiC particle size. However, when the SiC particle size is larger than a certain size and its content is greater than 10 %, the friction coefficient suddenly decreases. In the surface observations after friction tested specimens, the element mapping image shows the Mg ratio relative to Si ratio (=SiC) increases with reducing friction coefficient. This indicates that good wear resistance is due to the presence of self-formed SiC layers during the friction process. [ABSTRACT FROM AUTHOR]

المؤلفون: Sharma, Vivek¹ (AUTHOR), Mallick, Ashis¹ (AUTHOR) mal123_us@yahoo.com, Joardar, Joydip² (AUTHOR), Kumar, Shakti¹ (AUTHOR), Konovalov, S. V.³ (AUTHOR)

المصدر: Arabian Journal for Science & Engineering (Springer Science & Business Media B.V. ). Aug2024, Vol. 49 Issue 8, p11623-11634. 12p.

مصطلحات موضوعية: *MECHANICAL alloying, *POWDER metallurgy, *INTERMETALLIC compounds, *WEAR resistance, *ALLOY powders, *MICROSTRUCTURE

مستخلص: A multicomponent bulk nanostructured Al20Ti20Fe20Mn20Ni20 high-entropy alloy (HEA) was prepared by the powder metallurgy method. The process involved mechanical alloying of the elemental powders of equal wt% followed by cold compaction and conventional sintering in an inert atmosphere at different temperatures. The structural evaluation and morphological studies of the milled powders were carried out by HRTEM and XRD analysis. The crystal size and d-spacing of the milled powder significantly reduced with the milling duration. The effects of sintering temperatures on the microstructure, wear resistance, and the hardness of Al20Ti20Fe20Mn20Ni20 were investigated. The microstructural analysis showed that the prepared HEAs had a multiphase microstructure consisting of BCC and intermetallic compounds. As the sintering temperature grew, the microhardness and wear resistance increased, demonstrating that the properties of the current HEA were improved by using high sintering temperatures. The increase in density with sintering temperatures and the intermetallic phase contents acted as reinforcement might have enhanced the hardness of the HEA. The best hardness value and the least amount of wear were found in the sample sintered at 900 °C. [ABSTRACT FROM AUTHOR]

المؤلفون: JAEYOON BAE¹, SUMIN LEE¹, KUNOK CHANG², DJAMEL KAOUMI³, SANGHOON NOH¹ nohssang@pknu.ac.kr

المصدر: Archives of Metallurgy & Materials. 2024, Vol. 69 Issue 2, p421-424. 4p.

مصطلحات موضوعية: *ALLOY powders, *POWDER metallurgy, *MECHANICAL alloying, *HEAT treatment, *HOT pressing, *HIGH temperatures

مستخلص: Ni-16Mo and ODS alloys were fabricated by the powder metallurgical processes, and their microstructures and tensile properties were investigated. Ni-16Mo-7Cr and Ni-16Mo-7Cr-0.3Ti-0.35Y2O3 (in wt.%) alloys were prepared by mechanical alloying, uniaxial hot pressing, and heat treatment processes. Microstructural observations of these alloys revealed that the Ti and Y2O3 additions to a Ni-16Mo alloy were significantly effective to refine the grain size and form nano-sized Y-Ti-O oxide particles. Consequently, the tensile strengths at room temperature and 700°C were considerably enhanced. This improvement of tensile properties can be mainly attributed to the formation of nano-sized oxide particles, as well as the refined grain size. It is thus concluded that Ni-16Mo alloy with Ti and Y2O3 additions would be very effective in improving the mechanical properties especially at elevated temperatures. [ABSTRACT FROM AUTHOR]

المؤلفون: Moustafa, Essam B.¹ (AUTHOR), Aljabri, Abdulrahman² (AUTHOR), Abushanab, Waheed S.³ (AUTHOR), Ghandourah, E.⁴ (AUTHOR), Taha, Mohammed A.⁵ (AUTHOR), Khoshaim, Ahmed B.¹ (AUTHOR), Youness, Rasha A.⁶ (AUTHOR) rhakamnrc@gmail.com, Mohamed, S. S.⁷ (AUTHOR)

المصدر: Scientific Reports. 2/4/2024, Vol. 14 Issue 1, p1-15. 15p.

مصطلحات موضوعية: *POWDER metallurgy, *THERMAL expansion, *YOUNG'S modulus, *PARTICLE size distribution, *POWDERS, *MECHANICAL wear

مستخلص: More focus has recently been placed on enhancing the strength, elastic modulus, coefficient of thermal expansion (CTE), wear and corrosion resistance, and other qualities of aluminum (Al) alloys by varying the quantity of ceramics added for a range of industrial uses. In this regard, Al-4.2-Cu-1.6Mg matrix nanocomposites reinforced with nano-ZrO2 particles have been created using the powder metallurgy approach. The microstructure and particle size distributions of the produced powders were analyzed using a diffraction particle size analyzer, XRD, TEM, and SEM. To achieve good sinterability, the powders were compacted and sintered in argon. The sintered nanocomposites' mechanical, elastic, and physicochemical characteristics were measured. Additionally, the behavior of corrosion, wear, and thermal expansion were examined. The results showed a decrease in the particle sizes of the Al-Cu-Mg alloy by adding ZrO2 nanoparticles up to 45.8 nm for the composite containing 16 wt.% ZrO2. By increasing the sintering temperature to 570 °C, the densification of nanocomposites was enhanced. Also, the coefficient of thermal expansion and wear rate remarkably decreased by about 28 and 37.5% by adding 16 wt.% ZrO2. Moreover, microhardness yield, strength, and Young's modulus were enhanced to 161, 145, and 64%, respectively, after adding 16 wt.% ZrO2. In addition, increasing the exposure time was responsible for decreasing the corrosion rate for the same sample. [ABSTRACT FROM AUTHOR]

المؤلفون: Ling, Chen^1,2 (AUTHOR) sdulingchen@mail.sdu.edu.cn, Ren, Xiaoping^1,2 (AUTHOR) renxiaoping@sdu.edu.cn, Wang, Xuepeng^1,2 (AUTHOR) 202334403@mail.sdu.edu.cn, Li, Yinghao^1,2 (AUTHOR) melius@sdu.edu.cn, Liu, Zhanqiang^1,2 (AUTHOR) sduwangbing@sdu.edu.cn, Wang, Bing^1,2 (AUTHOR) sduzhaojinfu@sdu.edu.cn, Zhao, Jinfu^1,2 (AUTHOR)

المصدر: Materials (1996-1944). Feb2024, Vol. 17 Issue 3, p670. 19p.

مصطلحات موضوعية: *STRAIN rate, *POWDER metallurgy, *HIGH temperature metallurgy, *MECHANICAL behavior of materials, *HEAT resistant alloys, *RECRYSTALLIZATION (Metallurgy)

مستخلص: The material undergoes high temperature and high strain rate deformation process during the cutting process, which may induce the dynamic recrystallization behavior and result in the evolution of dynamic mechanical properties of the material to be machined. In this paper, the modified Johnson-Cook (J-C) model for nickel-based powder metallurgy superalloy considering dynamic recrystallization behavior in high strain rate and temperature is proposed. The dynamic mechanical properties of the material under different strain rates and temperature conditions are obtained by quasi-static compression test and split Hopkinson pressure bar (SHPB) test. The coefficients of the modified J-C model are obtained by the linear regression method. The modified model is verified by comparison with experimental and model prediction results. The results show that the modified J-C model proposed in this paper can accurately describe the mechanical properties of nickel-based powder metallurgy superalloys at high temperatures and high strain rates. This provides help for studying the cutting mechanism and finite element simulation of nickel-based powder metallurgy superalloy. [ABSTRACT FROM AUTHOR]