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Search Results: 1 - 10 of 6319 matches for " mechanical alloying "
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Evaluation of HEBM Mechanical Alloying of Al2O3—356/7075 Powder Mixture  [PDF]
G. Govender, Lilian Ivanchev, H. Burger, A. Mulaba, H. Chikwande
Open Journal of Composite Materials (OJCM) , 2012, DOI: 10.4236/ojcm.2012.22007
Abstract: Particle reinforced aluminium alloy metal matrix composites (MMC) have proven to be one of the advanced materials capable of replacing conventional structural alloys. However, the demand for such materials has been confined to high cost applications due to their complex processing. A preliminary mechanical alloying (MA) of metal powder with ce-ramic particulates by High Energy Ball Mill (HEBM) processing is a step of MMC manufacturing process. In this paper mechanical alloying of aluminium alloys A356 and 7075 powder with Al2O3 and SiC par-ticulates using two types of HEBM was investigated. The effect of dispersed phase strengthening mechanism on three aluminium grade alloys was evaluated by micro hardness measurement. Microstructure investigation confirms the achieved strengthening results. It was established that by measuring hardness of alloyed aluminium particles with low load reliable information on the alloying effect can be achieved.
Structural, Microstructral, Mechanical and Magnetic Characterization of Ball Milled Tungsten Heavy Alloys  [PDF]
H. Elshimy, Z. K. Heiba, Karimat El-Sayed
Advances in Materials Physics and Chemistry (AMPC) , 2014, DOI: 10.4236/ampc.2014.412027
Abstract: A homemade ball mill was constructed and optimized in order to prepare nano crystallite size of tungsten heavy alloys, with composition of 90W-7Ni-3Fe and 90W-7Ni-3Co in wt%. The samples were mechanically alloyed under high purity of argon atmosphere and were sintered under high vacuumat 1200°C, 1300°C and 1400°C. X-ray diffraction (XRD), Transmission Electron Microscope (TEM), Scanning Electron Microscope (SEM), Energy Dispersive X-ray (EDX), Vickers, ultrasonic techniques and SQUID magnetometer were all used to characterize the studied samples. The sintering temperature and the milling time at which the heavy tungsten alloys were obtained, are discussed in details. The results showed that the tungsten heavy alloys were synthesized and sintered at lower temperature than those prepared by the conventional techniques. Moreover, the strains and relative densities increased with milling time up to 100 hrs; then decreased with further milling. On the other hand, the elastic moduli and hardness increased with milling time up to 200 hrs; then decreased with further milling. The hardness calculated from ultrasonic and measured from Vickers exhibited a similar trend though with different values. The saturated magnetization decreased by increasing the milling time and decreasing the crystallite size.
STUDY OF THE Fe-75%Ag SYSTEM OBTAINED BY MECHANICAL ALLOYING
Bonyuet,D; González,G; Ochoa,J; Gonzalez-Jimenez,F; D′Onofrio,L;
Revista Latinoamericana de Metalurgia y Materiales , 2002,
Abstract: mechanical alloying (ma) is a powder processing technique, which allows us to induce solid state reactions in binary systems immiscible in equilibrium. fe and ag have a mutually repulsive nature that makes them completely immiscible under thermodynamically stable conditions. the ball milling process being a non-equilibrium technique seems promising in obtaining at least a partial solid solution in this system. mixtures of fe and ag powders with 75 wt% ag were studied by x-ray diffraction (xrd), scanning electron microscopy (sem) and transmission electron microscopy (tem). we have found that it is possible to obtain a small mutual solid solution in this system by ma. this is also confirmed by m?ssbauer spectroscopy.
Formation of ε-FexN/BN magnetic nanocomposite and its thermodynamic and kinetic analyses
Li Liu,Bin Yao,Hongyan Wang,Fushan Li,Bingzhe Ding,Wenhui Su
Chinese Science Bulletin , 1998, DOI: 10.1007/BF02883810
Abstract: A nanocomposite of nanometer-sized magnetic granular ε-FexN embedded in a nonmagnetic amorphous boron nitride matrix was prepared by ball milling mixture of α-Fe and hexagonal boron nitride in argon atmosphere. The grain size of the ε-FexN alloy was about 10–20 nm. The nitrogen concentration in the ε-FexN alloy increases with extending milling time. Both thermodynamic calculation and the present experiment show that iron and nitrogen atoms have higher alloying driving force than iron and boron atoms. Analyses of thermodynamics and kinetics about formation of the ε-FexN alloy suggested that the formation of the ε-FexN alloy is related to amorphization of the hexagonal boron nitride and refinement of the α-Fe. It was found from the present experiment that a critical grain size of the α-Fe reacting with nitrogen in the amorphous boron nitride is about 8 nm.
Development of Fe-Cr-Ni-Mn-N High-Alloyed Powder Processed by Mechanical Alloying  [PDF]
Anatoly A. Popovich,Nikolay G. Razumov,Alexey O. Silin,Evgeniy L. Gulihandanov
Open Journal of Metal (OJMetal) , 2013, DOI: 10.4236/ojmetal.2013.32a2004
Abstract: The present work shows the research results of phase formation in obtaining high-alloy powder of Fe-Cr-Ni-Mn-N by mechanochemical synthesis in various gas atmospheres.
Development of Fe-Cr-Ni-Mn-N High-Alloyed Powder Processed by Mechanical Alloying  [PDF]
Anatoly A. Popovich, Nikolay G. Razumov, Alexey O. Silin, Evgeniy L. Gulihandanov
Open Journal of Metal (OJMetal) , 2013, DOI: 10.4236/ojmetal.2013.32A2004
Abstract: The present work shows the research results of phase formation in obtaining high-alloy powder of Fe-Cr-Ni-Mn-N by mechanochemical synthesis in various gas atmospheres.
Structural Characterization of Nanocrystalline Ni(50-x)Ti50Cux (X = 5, 9 wt%) Alloys Produced by Mechanical Alloying  [PDF]
Bahman Nasiri-Tabrizi, Abbas Fahami
Advances in Nanoparticles (ANP) , 2013, DOI: 10.4236/anp.2013.22013
Abstract:

Nanocrystalline Ni(50-x)Ti50Cux(X = 5, 9 wt%) alloys were successfully produced by mechanical alloying. Mechanical activation was performed at different milling times under a high purity argon (99.998 vol%) atmosphere. Phase analysis and structural features of the samples were examined by X-ray diffraction (XRD). Results revealed that NiTiCu (B2) phase was achieved after 600 min of milling. The formation of this phase was mostly related to the critical factors in determining the site replacement of elements in Ni-Ti-Cu ternary system. After 600 min of milling, the average crystallite size and lattice strain of the samples were about 5 - 10 nm and 1.057% - 1.967%, respectively. Evaluation of the full width at half maximum (FWHM) values for all the samples indicated the occurrence of anisotropic line broadening. The determined amounts of crystallinity revealed that the fraction of crystalline phase decreased with increasing weight percentage of copper up to 9% and reached a minimum value after 600 min of milling. The lattice parameters and the unit cell volume of the milled samples were always larger than the standard values. In addition, lattice parameter deviation influenced by the weight percentage of copper. Based on the obtained data, mechanical alloying process can be used for production of nanocrystalline NiTiCu alloys with different structural features.

Structural and Morphological Study of a Series of Ball Milled Nanocrystalline Fe1-xAlx (0.3 ≤ x ≤ 0.6) Alloys  [PDF]
Sandeep Rajan, Rajni Shukla, Anil Kumar, Anupam Vyas, Ranjeet Brajpuriya
Journal of Modern Physics (JMP) , 2014, DOI: 10.4236/jmp.2014.58075
Abstract:

In the present manuscript, the authors have systematically investigated the structural and morphological properties of a series of mechanically alloyed Fe1-xAlx (0.3 ≤ x ≤ 0.6) samples using X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). All the samples, after 5 hr of milling, show crystalline structure, irrespective of the constituent concentration and are textured mainly along (110) direction. In Fe-rich samples, the formation of an off-stoichiometric Fe3Al phase is favored and in case of Al-rich samples, both Al-rich phases and clustering of Al atoms are present. Analysis of line breadths was carried out to get an insight into the interrelated effects of average crystallite size, and lattice parameters. The grain size of constituents was decreased to the nanometer range (between 6 - 8 nm) and the constituents dissolved at the nanograin boundaries. Similar conclusions were also revealed from the SEM results which show that the initial shape of particles disappeared completely, and their structure became a mixture of small and large angularshaped crystallites with different sizes. The results of this research could be directly employed in the design of deformation schedules for the industrial processing of Fe-Al alloys.

Effect of Milling Time on Co0.5Zn0.5Fe2O4 Microstructure and Particles Size Evolution via the Mechanical Alloying Method  [PDF]
Abubakar Yakubu, Zulkifly Abbas, Mansor Hashim, Ahmad Fahad
Journal of Materials Science and Chemical Engineering (MSCE) , 2014, DOI: 10.4236/msce.2014.211008
Abstract: Nanocrystalline CoZn-ferrite was fabricated by a high-energy milling method by mixing Fe3O4+CoO+ZnO. The structural properties of the milled powder at different milling times were analysed so to ascertain the diffusion of CoO and ZnO into the tetrahedral and octahedral sites using mechanical alloying method. The effect of mechanical alloying towards particle size was also investigated. The XRD spectra indicated the precursors reacted during milling with the diffusion of ZnO and followed by CoO into their respective crystallographic sites. SEM micrographs showed the agglomeration of powders due to high energy milling and TEM images confirmed that the particles of the materials were of nanosize dimension. In addition, the results show that the grain possesses a single-phase CoZn-ferrite structure in a typical size of ~16–30 nm. The experiment reveals that nanosize CoZn-ferrite can be obtained after the powder is milled for about 8 hours at room temperature. The mechanism and efficiency of the synthesis of the technique are also discussed in this paper.
Synthesis and Densification of Tungsten-Brass Composite by Mechanical Alloying  [PDF]
Kahtan S. Mohammed, Baba Gowon, Shamsul Baharin Bin Jamaluddin, Zuhailawati Hussain, Polycarp Evarastics
Open Journal of Metal (OJMetal) , 2015, DOI: 10.4236/ojmetal.2015.53004
Abstract: Fabrication of full-density W-brass composites is very difficult to achieve because of evaporation of zinc, insolubility of W and brass and compacts expansion. In this study, to achieve full-density W-brass composites, mechanical alloying (MA) and activated sintering process were utilized. Mechanical coating of W with Ni using high energy planetary ball mill was carried out. The milling was divided into two stages: to alloy and modify the surface of W with Ni for enhanced activation. The microstructure of the milled powders and sintered compacts, elemental composition and phases present were studied by using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) respectively. As-received powder compacts was also sintered under the same condition for comparison purpose. The effects of milling time on the microstructure, sinterability and the hardness of the composites were investigated. It was observed that the samples produced from 8 h milled powder had the highest relative sintered density (98% TD) and microhardness (234 Hv). On the other hand, the samples from the as-received powders expanded and had a relative sintered density of (67% TD) and microhardness as low as 24 Hv. The significance of this study is the possibility of producing W-brass composites as a cheaper alternative to W-Cu composites.
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