Undercooling and Rapid Solidification of Nb-Si Eutectic Alloys Studied by Long Drop Tube

Niobium-silicide alloys have great potential for high temperature turbine applications. The two-phase Nb/Nb5Si3 in situ composites exhibit a good balance in mechanical properties. Using the 52 in drop tube, the effect of undercooling and rapid solidification on the solidification process and micro-structural characterization of Nb-Si eutectic alloy was studied. The microstructures of the Nb-Si composites were investigated by optics microscope (OM), X-ray diffraction (XRD) and scanning electron microscope (SEM) equipped with X-ray energy dispersive spectrometry (EDS). Up to 480 K, deep undercooling of the Nb-Si eutectic samples was successfully obtained, which corresponds to 25% of the liquidus temperature. Contrasting to the conventional microstructure usually found in the Nb-Si eutectic alloy, the microstructure of the undercooled sample is divided into the fine and coarse regions. The most commonly observed microstructure is Nb+Nb5Si3, and the Nb3Si phase is not be found. The change of coarseness of microstructure is due to different cooling rates during and after recalescence. The large undercooling is sufficient to completely bypass the high temperature phase field.

Caracterización estructural y magnética de aleaciones intermetálicas Fe-Al-Si mediante espectroscopia Mössbauer

253 p.

射频磁控溅射制备掺Al的纳米Si-SiO_2复合薄膜及其光致发光特性

采用射频磁控技术和退火处理制备掺Al的纳米Si-SiO_2复合薄膜.通过X射线衍射(XRD)、X射线光电子能谱(XPS)和傅里叶变换红外光谱(FTIR)表征了薄膜的结构,组分和成键情况.掺Al在SiO_2中造成氧空位,使薄膜光致发光强度增强,并出现新的发光峰.退火温度对掺Al薄膜的光致发光的峰位和峰强有较大影响.

~(40)Ar~(10+)轰击Al和Si固体表面形成的200～1000nm光谱

报道了利用兰州重离子加速器国家实验室ECR离子源提供的高电荷态离子~(40)Ar~(10+)入射到Al和p型Si表面所产生的Al,Si,Ar原子的200～1000nm特征光谱的实验测量结果。结果表明,低速高电荷态离子与团体表面原子相互作用可有效地激发靶原子和靶离子的特征谱线,而且由于发射二次电子的无辐射退激与辐射光子退激过程的竞争,使得在p型Si表面上Ar原子的光谱强度总体大于在Al表面上的光谱强度。

Modelación de la transferencia de calor en una aleación Al-Si tipo 319 [por] Jesús Talamantes Silva

Tesis (Maestría en Ciencias de la Ingeniería Mecánica con Especialidad en Materiales) U.A.N.L.

Efecto de la temperatura de solubilización sobre las propiedades mecánicas en una aleación AL-SI tipo A319 [por] César Gerardo Dimas Acevedo

Tesis (Maestría en Ciencias de la Ingeniería Mecánica con Especialidad en Materiales) U.A.N.L.

Estudios de deformación cíclica en una aleación Al-Si tipo A319 por José Iván Suárez Gutiérrez

Tesis (Maestría en Ciencias de la Ingeniería Mecánica con Especialidad en Materiales) U.A.N.L.

Fractografía autoafín 3 D en una aleación Al-Si

Tesis ( Maestro en Ciencias de la Ingeniería Mecánica con Especialidad en Materiales) U.A.N.L.

Disolución de la fase teta en una aleación AL-SI con tres diferentes contenidos de cobre

Tesis ( Maestro en Ciencias de la Ingeniería Mecánica con Especialidad en Materiales) U.A.N.L.

Estudio de adhesibilidad entre una aleación de aluminio A319.0 y una camisa de aluminio base Al-Si-Cu-MG. para aplicaciones automotrices

Teis ( Maestro en Ciencias de Ingeniería Mecánica con Especialidad en materiales) U.A.N.L.

Efecto del zinc en las propiedades mecánicas de una aleación Al-Si tipo A319.

Tesis (Maestro en Ciencias de la Ingeniería Mecánica con Especialidad en Materiales) UANL, 2012.

Efecto de la microestructura y las variables de solidificación sobre el comportamiento a fatiga de alto ciclo en una aleación hipereutéctica AL-SI-CU-NI.

Tesis (Doctor en Ingeniería de Materiales) UANL, 2012.

Corrosion and tribocorrosion behaviour of Al-Si-Cu-Mg alloy and its composites reinforced with B4C particles in 0.05M NaCl solution

The corrosion behaviour of metal matrix composites (MMCs) is strictly linked with the presence of heterogeneities such as reinforcement phase, microcrevices, porosity, secondary phase precipitates, and interaction products. Most of the literature related to corrosion behaviour of aluminium matrix composites (AMCs) is focused on SiC reinforced AMCs. On the other hand, there is very limited information available in the literature related to the tribocorrosion behaviour of AMCs. Therefore, the present work aims to investigate corrosion and tribocorrosion behaviour of Al-Si-Cu-Mg alloy matrix composites reinforced with B4C particulates. Corrosion behaviour of 15 and 19% (vol) B4C reinforced Al-Si-Cu-Mg matrix composites and the base alloy was investigated in 0.05M NaCl solution by performing immersion tests and potentiodynamic polarisation tests. Tribocorrosion behaviour of Al-Si-Cu-Mg alloy and its composites were also investigated in 0.05M NaCl solution. The tests were carried out against alumina ball using a reciprocating ball-on-plate tribometer. Electrochemical measurements were performed before, during, and after the sliding tests together with the recording of the tangential force. Results suggest that particle addition did not affect significantly the tendency of corrosion of Al-Si-Cu-Mg alloy without mechanical interactions. During the tribocorrosion tests, the counter material was found to slide mainly on the B4C particles, which protected the matrix alloy from severe wear damage. Furthermore, the wear debris were accumulated on the worn surfaces and entrapped between the reinforcing particles. Therefore, the tendency of corrosion and the corrosion rate decreased in Al-Si-Cu-Mg matrix B4C reinforced composites during the sliding in 0.05M NaCl solution. © 2013 Elsevier B.V.