Papers by Keyword: Mechanical Alloying

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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: Amir Reza Shirani-Bidabadi, Ali Shokuhfar, Mohammad Hossein Enayati, Mazda Biglari
Abstract: In this research, the formation mechanisms of a (NiCr)Al-Al2O3 nanocomposite were investigated. The structural changes of powder particles during mechanical alloying were studied by X-ray difractometry (XRD) and the morphology and cross sectional microstructure of powder particles were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The methodology involved mechanical alloying of NiO, Cr, and Al with molar ratios of 3:3:8. During mechanical alloying, NiO was first quickly reduced by aluminum atoms to produce NiAl nanocrystalline and Al2O3. Subsequently, and when a longer milling time was applied, chromium atoms diffused into the NiAl lattice. The heat treatment of this structure led to the formation of the (NiCr)Al intermetallic compound as well as Al2O3 with crystalline sizes of 23 nm and 58 nm, respectively.
Authors: Ping Luo, Shi Jie Dong, Zhi Xiong Xie, Wei Yang, An Zhuo Yangli
Abstract: TiC-TiB2 composite ceramics were successfully fabricated via planetary ball milling of 72 mass% Ti and 28 mass % B4C powders, followed by low temperature sintering process at 1200°C. The microstructure of the ball-milled powder mixtures and composite ceramics were characterized by Differential thermal analysis equipment (DTA), field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The results showed that the ball-milled powder mixtures (Ti and B4C powders) were completely transformed to TiC-TiB2 composite ceramics as the powders were milled for 60 h and sintered at 1200°C for 1 h. The formation mechanism of the TiC-TiB2 composite was discussed. The high energy ball milling and necessary sintering for the powder mixtures plays an important role in the formation of the composites.
Authors: Peng Fei Zhang, De Chang Jia, Bin Yang, Guang Xin Wang
Abstract: A mixture of cubic silicon powder, hexagonal boron nitride powder and graphite powder was mechanically alloyed for 30 hrs in argon. The as-milled 2Si-B-3C-N composite powder was heated up to 1900 °C in nitrogen, with a heating rate of 25 °C/min and under a pressure of 80 MPa. XRD and HRTEM results show that the as-milled 2Si-B-3C-N composite powder has a well amorphous structure. Under the current hot-pressing circumstances, the amorphous ceramic starts to crystallize at a temperature between 1800 °C and 1900 °C. Once the temperature is higher than crystallization temperature, crystallites appear in the amorphous matrix with a great nucleation rate, but a small growth rate. Hot pressed at 1900 °C for 0 mins or 10 mins, the prepared 2Si-B-3C-N bulk ceramic has an average grain size of 8.7 nanometers and 22.3 nanometers, respectively. After an intensive literature search, we believe the present work is the first one to make clear that it is possible to use the mechanical alloying route to prepare amorphous Si-B-C-N ceramic with such a high crystallization temperature.
Authors: Yu Ying Zhu, Qiang Li, Yun Hua He, Ge Wang, Xing Hua Wang
Abstract: A new quaternary amorphous alloy powder Ti50Fe22Ni22Sn6 are prepared by mechanical alloying. The milling was performed under an argon atmosphere in a high-energy planetary ball mill. After milled 70h, fully amorphous Ti50Fe22Ni22Sn6 powders can be obtained, with the condition of the milling speed, 300rpm, and the weighs ratio of ball to powder, 10:1. Crystal structure of the milled powders is investigated by XRD. Thermal analysis show that when the heating rate increasing from 10K/min to 40K/min, the super-cooled liquid region of milled amorphous alloy increased from 93K to 110K.
Authors: S. Bergheul, Fadhela Otmane, Z. Hamlati, M. Azzaz
Abstract: In this work, we study the synthesis of Fe-Co powders via planetary ball milling with different particle sizes. The morphology is a factor that influences the microwave properties of materials. The prepared samples are characterized using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), X-band wave guide and resonator cavity associated with network analysis. The microwave-absorbing characteristic effects are investigated in a frequency range 8.5–10.5 GHz using network analyser. They enhanced between 0 and 54 h of milling time with an increase in the relative dielectric permittivity (ε'r).
Authors: Cai Yun Shang, Yan Wang
Abstract: The AlCrFeNi high entropy coating was successfully prepared by mechanical alloying and vacuum hot pressing sintering technique on Q235 steel substrate, and the microstructures and microhardness, wear resistance and corrosion resistance were characterized in detail. Results showed that single body-centered cubic solid solution phase appears when the blended powder is ball milled for 30 h. The vacuum hot pressing sintered AlCrFeNi high entropy coating with single BCC solid solution is about 500 μm in thickness, which metallurgically bonded to substrate. The microhardness of the AlCrFeNi high entropy coating is about 520 HV, more than three times larger than that of the substrate. The wear resistance and corrosion resistance of the coating in 3.5% NaCl solution are greatly improved compared with the substrate, showing a dramatic reduction in average corrosion rate and wider passive range.
Authors: Petr Urban, Eduardo Sanchez Caballero, Fatima Ternero, Francisco Javier Viña Reina, Francisco Gomez Cuevas
Abstract: This paper focuses on the microstructural characterization of Al25Ti75, Al37Ti63, Al50Ti50, Al63Ti37 and Al75Ti25 powders mixtures prepared by mechanical alloying (MA). The high-energy ball-milling, up to 75 h, of aluminium and titanium powders leads to a nanocrystalline or an amorphous structure. It is showed that a stable amorphous Al–Ti phase with uniform elemental distribution forms after 50 h of milling in Al50Ti50 alloy. Heat treatment of the different alloys leads to the crystallization of AlTi3, AlTi, Al2Ti and Al3Ti intermetallic compounds. A comprehensive study by laser granulometry, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC) was carried out on the structure, surface morphology and thermal behaviour of the MA Al-Ti mixtures, both of milled and heat treated powders.
Authors: Viktor Vekky Ronald Repi, Azwar Manaf
Abstract: We have investigated of composite (1-x)Ba0.5Sr0.5Fe11.7Mn0.15Ti0.15 / xLa0.7Ba0.3MnO3 by conventional ceramic method. The sturcture of composite and complex impedance are carried out by XRD, SEM and Impedance Spectroscopy. With changing the weight ratio from x=0; 0.3; 0.5 and x=1 the phase exhibit the composite behavior. Very interestingly, for the case of the case of weight ratio x=0.5 and 0.7 showed the complex impedance with xemicircle pattern in frequency range from 1 KHz to 1 MHz.
Authors: Qing He, Hui Yang, Law Son Chen, Xian Ping Fan, Qian Hong Shen, Xin He Wu, Cheng Fa Mu, Ling Jie Zhang
Abstract: To diagnose the arc erosion type and improve arc erosion resistance of Ag/LSCO (Ag/La0.5Sr0.5CoO3-δ) contacts, making and breaking experiments were carried on Ag/LSCO(12) contacts prepared by both traditional powder metallurgy method and a modified one in this work. Arc erosion and morphological characters of this two kinds of Ag/LSCO(12) samples were investigated and the erosion mechanisms were also discussed. The results are that seven types of arc erosion morphologies of Ag/LSCO(12) contacts were classified as the lump region, the cauliflower region, the framework structure, holes and cavities, cracks, spongy region and the vestiges of fusant spreading. There are intrinsic links between these morphological characters. The spongy regions and vestiges of fusant spreading on the contact surface of Ag/LSCO(12) prepared by the new method indicates that its resistance to arc erosion is superior to the contacts prepared by traditional method.
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