Papers by Keyword: Aluminum (Al)

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Authors: Agus Sukarto Wismogroho, Wahyu Bambang Widayatno
Abstract: In this study a new technique for producing an Al/Al2O3 composite coating on a steel substrate by an in situ process was examined. The pre-treating of the steel substrate with Al was carried out by MA at room temperature, followed by MA using a low-energy ball mill at 200-500°C. An Al/Al2O3 coating layer with a homogenous distribution of Al2O3 particles were achieved. The coating layer has not only high hardness but also high fracture toughness.
Authors: Henri Nguyen-Thi, Jiang Wang, Georges Salloum-Abou-Jaoude, Guillaume Reinhart, Imants Kaldre, Nathalie Mangelinck, Zhong Ming Ren, Leonids Buligins, Andris Bojarevics, Yves Fautrelle, Olga Budenkova, Tamzin Lafford
Abstract: It is well known that the application of a magnetic field during the growth process can have pronounced effects on cast material structures and their properties, so that magnetic fields have been widely applied since the 1950s. In the case of a permanent magnetic field, some recent results revealed a dual effect on the liquid metal flow. 1: the magnetic field has a selective damping action on the flow at the scale of the crucible, due to the Lorentz force; 2: the interaction of thermo-electro-magnetic (TEM) currents in the close vicinity of the solid-liquid interface with the applied magnetic field leads to the generation of electromagnetic forces, which act both on the liquid and on the solid at the scale of the microstructure. We present an experimental investigation of the TEM forces induced by a permanent magnetic field during columnar and equiaxed solidification of Al-4wt%Cu. In situ visualization was carried out by means of synchrotron X-ray radiography, which is a method of choice for studying dynamic phenomena. It was shown that the TEM forces were at the origin of a motion of dendritic particles, perpendicular to the direction of gravity. A heuristic analysis allowed us to estimate the fluid velocities and the velocities of the solid particles, and a good agreement was achieved with the experimental data. Similar observations were also made during equiaxed growth in a temperature gradient. The in situ observation of the grain trajectories for various values of the temperature gradient demonstrated that gravity and TEM forces were the driving forces which controlled the grain motion.
Authors: Guo Sheng Sun, Yong Mei Zhao, Liang Wang, Lei Wang, Wan Shun Zhao, Xing Fang Liu, Gang Ji, Yi Ping Zeng
Abstract: The in-situ p-type doping of 4H-SiC grown on off-oriented (0001) 4H-SiC substrates was performed with trimethylaluminum (TMA) and/or diborane (B2H6) as the dopants. The incorporations of Al and B atoms and their memory effects and the electrical properties of p-type 4H-SiC epilayers were characterized by secondary ion mass spectroscopy (SIMS) and Hall effect measurements, respectively. Both Al- and B-doped 4H-SiC epilayers were p-type conduction. It was shown that the profiles of the incorporated boron and aluminum concentration were in agreement with the designed TMA and B2H6 flow rate diagrams. The maximum hole concentration for the Al doped 4H-SiC was 3.52×1020 cm-3 with Hall mobility of about 1 cm2/Vs and resistivity of 1.6~2.2×10-2 Wcm. The heavily boron-doped 4H-SiC samples were also obtained with B2H6 gas flow rate of 5 sccm, yielding values of 0.328 Wcm for resistivity, 5.3×1018 cm-3 for hole carrier concentration, and 7 cm2/Vs for hole mobility. The doping efficiency of Al in SiC is larger than that of B. The memory effects of Al and B were investigated in undoped 4H-SiC by using SIMS measurement after a few run of doped 4H-SiC growth. It was clearly shown that the memory effect of Al is stronger than that of B. It is suggested that p-type 4H-SiC growth should be carried out in a separate reactor, especially for Al doping, in order to avoid the join contamination on the subsequent n-type growth. 4H-SiC PiN diodes were fabricated by using heavily B doped epilayers. Preliminary results of PiN diodes with blocking voltage of 300 V and forward voltage drop of 3.0 V were obtained.
Authors: Sandrine Coste, Ghislaine Bertrand, Christian Coddet, Eric Gaffet, Horst Hahn, H. Sieger, M.A. Rodriguez, Cathy Meunier, Serge Vives
Abstract: Superior properties of nanostructured Al2O3 based materials, such as higher hardness and fracture toughness, have been evidenced. In order to optimize their manufacturing, the mechanical activation of the starting powders (Al2O3-TiO2 and Al2O3-ZrO2) was studied. In the present work, Al2O3 powders blended with 13wt% and 44wt% of titania or 20wt% and 80wt% of yttria partially stabilized zirconia have been high-energy ball-milled using a planetary mill, P4 (Fritsch) with steel vials and balls. The effect of the milling time and operating parameters, such as shock energy and friction to total energy ratio, on the powder structural and microstructural evolutions has been determined by SEM, XRD and BET. The transformation of the metastable anatase TiO2 phase into the high pressure TiO2 II phase and rutile phase was evidenced, simultaneously to the decrease of the alumina crystallite size, in the Al2O3-TiO2 system. In the Al2O3-ZrO2 system, the transformation of the monoclinic phase and the decrease of the alumina and tetragonal zirconia crystallite size have been observed.
Authors: Hironobu Oonishi, N. Murata, M. Saito, S. Wakitani, K. Imoto, S. Kin, Y. Chen, H. Nakaya, M. Tanaka, H. Amino
Authors: W.H. Liu, Xin Ming Zhang, Jian Guo Tang, Yu Xuan Du
Abstract: Void growth in aluminum single crystals is simulated using the finite element method, to illustrate the effect of grain orientation on void growth, a rate dependent crystal plasticity constitutive theory is implemented as a user-defined plasticity subroutine. A three-dimension unit cell including a sphere void was employed using three-dimensional 12 active slip systems. The computed results for several grain orientations are compared, which have shown that crystallographic orientation has significant influence on growth behavior of void. And the void growth direction and shape significantly depend on the crystallographic orientation. Due to plastic flow localization and anisotropic behavior, void which has an initial sphere shape, develops an irregular shape and some corners.
Authors: Zsuzsanna Sükösd, Kristofer Hannesson, Gui Lin Wu, Dorte Juul Jensen
Abstract: The distribution of nucleation sites in 90% cold rolled aluminium (AA1050) annealed for 1h at 280°C has been determined by serial sectioning the sample and characterizing each section using the electron back scattering pattern (EBSP) method in the SEM. In total 1844 nuclei are identified. It was found that the nuclei are not randomly distributed but clustered preferentially along TD-RD planes in the sample. The results are presented and implications of clustered nucleation on recrystallization kinetics are discussed.
Authors: R.H.L. Garcia, Valter Ussui, Nelson Batista de Lima, Dolores Ribeiro Ricci Lazar
Abstract: The addition of alumina in a zirconia stabilized in a tetragonal phase matrix enhances ceramic hardness and inhibits the tetragonal → monoclinic phase transformation of zirconia when exposed to an aqueous environment. These characteristics are important for applications such as bioceramics and structural materials. For these purposes, the strict control of powder synthesis and the processing conditions are vital to tailor the ceramic characteristics. This work evaluates the influence of 20 wt% alumina in a Y-TZP matrix on powder characteristics, obtained by coprecipitation route, and calcined from 600 to 1200°C for 1 and 3 hours. The powders obtained were characterized by X-ray diffraction, scanning electronic microscopy, laser diffraction and gaseous adsorption (BET). The results reveal that presence of Al3+ inhibits the crystallization of composite at lower temperatures.
Authors: Sravan Kumar Josyula, Suresh Kumar Reddy Narala
Abstract: Aluminum based Titanium carbide particulate reinforced metal matrix composite (Al-TiC PMMC) draws attention by many researchers & industries over alloy materials because of its excellent thermo-physical and mechanical characteristics. Despite of its superior properties of Al-TiC MMC, its complexity in manufacturing process and poor machinability has been the main deterrents to its application level. Controlling agglomeration of TiC particles is a challenging task to retain improved microstructure. The hard abrasive nature of carbide particles cause poor machinability and high machining cost. Therefore, in this paper an attempt has been made to study the various manufacturing techniques to achieve uniform distribution of TiC reinforcements in Al matrix.Further, the review follows the secondary manufacturing process of Al-TiC PMMC, which addressee’sthree topics: machining, forming & welding.
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