The Transformation of Co-Rich Alloys Produced by Mechanical Alloying

2006 ◽  
Vol 509 ◽  
pp. 135-140
Author(s):  
Francisco Cruz-Gandarilla ◽  
R. Gayosso-Armenta ◽  
J. Gerardo Cabañas-Moreno ◽  
Heberto Balmori-Ramírez

Elemental powder mixtures of Co and Ti were subjected to high-energy ball milling in order to produce mechanically alloyed powders with nominal compositions Co64Ti36, Co67Ti33, Co70Ti30, Co73Ti27, Co76Ti24 and Co85Ti15. The mechanically alloyed powders were treated during 30 minutes in inert atmosphere at temperatures in the range 300 – 700 °C. Both the as-milled powders as well as those subjected to heat treatments have been characterized by x-ray diffraction, scanning electron microscopy, energy-dispersive x-ray spectrometry and differential thermal analysis. As-milled products consist mostly of agglomerated powders with a size between 10 and 80 µm which give an amorphous-like diffraction pattern, except for the Co85Ti15 sample whose pattern presents the characteristic peaks of the Co3Ti intermetallic phase. The transformation of the asmilled powders occurs at temperatures in the range of about 530 – 670 °C with clearly observed exothermic events. The Co3Ti phase is found in all heat treated samples, together with fcc-Co (in Co76Ti24 and Co85Ti15) or the hexagonal Co2Ti intermetallic phase (in Co64Ti36, Co67Ti33 and Co70Ti30); the Co73Ti27 sample was essentially single-phase Co3Ti after heating to 700 °C. Our results suggest the occurrence of crystallization of an amorphous phase in two overlapping stages during heating of the mechanically alloyed powders.

2014 ◽  
Vol 592-594 ◽  
pp. 963-967
Author(s):  
Pravir Polly ◽  
K. Chandra Sekhar ◽  
Balasubramanian Ravisankar ◽  
S. Kumaran

In the present work, Al-5083-5wt% nanoyttria powders were milled for 10, 20, 30 and 35 hrs in a high energy ball milling under optimised process parameters. The milled powders were characterised by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Milled powders exhibit nanocrystalline single phase after 10hrs of milling. Consolidation of 35 hrs milled powder was done by equal channel angular pressing (ECAP) through 90odie channel angle using route A upto three passes with and without back pressure and sintered under controlled environment. Density of ECAPed samples was measured using Archimedes principle. The density is 96% for the sample consolidated with backpressure after two passes after sintering.


2016 ◽  
Vol 869 ◽  
pp. 19-24
Author(s):  
Lucas Moreira Ferreira ◽  
D.S. Mégda ◽  
A.C. de Souza ◽  
Rodrigo Fernando Costa Marques ◽  
Erika Coaglia Trindade Ramos ◽  
...  

This work evaluated on the structural modification during high-energy ball milling of the Si-50C, Si-42.9C-19.1B e Si-33.3C-44.4B (at.-%) powder mixtures from elemental powders. Electron images revealed on occurrence of continuous fracture mechanisms in brittle particles during their processing, which presented rounded particles lower than 10 μm. X-ray diffraction results of Si-50C powders indicated that the intensity of Si peaks was slightly reduced after milling for 17 h, which were moved to the direction of larger diffraction angles after 7 h of milling, suggesting that carbon atoms were dissolved into the Si lattice in order to form an extended solid solution. Following, these values were increased due to the discrete exothermic formation of the SiC compound. In Si-C-B powder mixtures, the SiC and B4C compounds were formed after milling for 7 h.


2008 ◽  
Vol 22 (18n19) ◽  
pp. 3233-3236 ◽  
Author(s):  
M. KHODAEI ◽  
F. KARIMZADEH ◽  
M. H. ENAYATI

In this study, hematite ( Fe 2 O 3) and aluminum ( Al ) powder mixtures were mechanically alloyed in a high-energy shaker ball mill to synthesize the iron-alumina ( Fe - Al 2 O 3) nanocomposite powder. The structural changes and phase developments occurring during mechanochemical process were studied by X-ray diffractometery (XRD) and scanning electron microscopy (SEM). The results showed that mechanochemical reaction of Fe 2 O 3 and Al completed after 3 hours of milling time in a nanocrystalline Fe and Al 2 O 3 embedded form and further milling produced a Fe - Al 2 O 3 nanocomposite powder. Kinetics consideration according to the calculated adiabatic temperature demonstrated the sudden displacement reaction during mechanical alloying that accord well with XRD results. Also, particle size decrease as well as crystallite size with increasing the milling time.


2014 ◽  
Vol 802 ◽  
pp. 66-71
Author(s):  
Rodrigo Estevam Coelho ◽  
D.B. Silvany ◽  
M.D.C. Sobral ◽  
M.C.A. Silva

In this works, aluminum scraps powders were mixed with commercial graphite and mechanically alloyed in a high-energy ball mill and subsequently powders sintering. The initial grinding of aluminum scraps for 2 hours and then mixed with commercial graphite powder at a proportion of (y)Al-(x)C (wt%) (x = 1, 5 e 10, 25). The mixture of aluminum and graphite powders was processed for a time at 5 hours of milling. The samples were sintered at a temperature of 750°C and 1000°C. Samples were analyzed by scanning electron microscopy and X-ray diffraction. The results of this study were to find important parameters of composition and sintering, because the increase in concentration of carbon in the aluminum indicates that the material may have different applications.


2014 ◽  
Vol 802 ◽  
pp. 51-55 ◽  
Author(s):  
Claudinei dos Santos ◽  
Alexandre Fernandes Habibe ◽  
Durval Rodrigues ◽  
José C. Minatti ◽  
Jefferson Fabrício C. Lins ◽  
...  

In this work, the microstructural features of the particles based on 66% Co-28% Cr-6% Mo alloy, were investigated by X-ray diffraction and Scanning electron microscopy (SEM). Powders obtained by high-energy ball milling in an inert atmosphere, and held in SPEX mill with times between 15min and 120min, about ball/powder ratio of 6:1, were characterized by X-ray diffraction indicating in all conditions, Co phase as the crystalline phase of the system. The powders have a morphology that indicate a continuous reduction in average particle size as a function of increasing time, however, the shape of the particles initially flat for times up to 30 minutes, becomes spherodized after 30 minutes of grinding.


2012 ◽  
Vol 727-728 ◽  
pp. 216-221 ◽  
Author(s):  
Perseu Amaral Nunes ◽  
Alfeu Saraiva Ramos ◽  
Erika Coaglia Trindade Ramos

This paper discusses on effect of molybdenum on the Ti6Si2B formation in mechanically alloyed and hot-pressed Ti-xMo-22Si-11B (x= 2, 5, 7 and 10 at%) alloys. High-energy ball milling and hot pressing were utilized to produce homogeneous and dense materials, which were characterized by scanning electron microscopy, X-ray diffraction, electron dispersive spectrometry, and Vickers hardness. The excessive agglomeration during milling was more pronounced in Mo-richer powders, which was minimized with the formation of brittle phases. Hot pressing of mechanically alloyed Ti-xMo-22Si-11B powders produced dense samples containing lower pore amounts than 1%. Ti6Si2B was formed in microstructure of the hot-pressed Ti-2Mo-22Si-11B alloy only. In Mo-richer quaternary alloys, the Ti3Si and Ti5Si3phases were preferentially formed during hot pressing. Oppositely to the ternary phase, the Ti3Si phase dissolved a significant Mo amount. Vickers hardness values were reduced in hot-pressed Ti-xMo-22Si-11B alloys containing larger Mo amounts, which were dissolved preferentially in Ti solid solution.


Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 755
Author(s):  
Leonid Vasylechko ◽  
Volodymyr Sydorchuk ◽  
Andrey Lakhnik ◽  
Yuriy Suhak ◽  
Damian Wlodarczyk ◽  
...  

Nanocrystalline compounds LiNb1−xTaxO3 of various compositions (x = 0, 0.25, 0.5, 0.75, 1) were synthesized by high-energy ball milling of the initial materials (Li2CO3, Nb2O5, Ta2O5) and subsequent high-temperature annealing of the resulting powders. Data on the phase composition of the nanopowders were obtained by X-ray diffraction methods, and the dependence of the structural parameters of LiNb1−xTaxO3 compounds on the value of x was established. As a result of the experiments, the optimal parameters of the milling and annealing runs were determined, which made it possible to obtain single-phase compounds. The Raman scattering spectra of LiNb1−xTaxO3 compounds (x = 0, 0.25, 0.5, 0.75, 1) have been investigated. Preliminary experiments have been carried out to study the temperature dependences of their electrical conductivity.


2017 ◽  
Vol 899 ◽  
pp. 3-8
Author(s):  
Luiz Otávio Vicentin Maruya ◽  
Bruno Bacci Fernandes ◽  
Mario Ueda ◽  
Alfeu Saraiva Ramos

This work reports on effect of magnesium addition on the Ti6Si2B stability in Ti-xMg-22Si-11B (x = 2 and 6 at.-%) alloys prepared by high-energy ball milling and subsequent sintering. Ball milling was conducted under Ar atmosphere in stainless steel vials and balls, 300 rpm, and a ball-to-powder weight ratio of 10:1. Following, the powders milled for 10 h were axially compacted in order to obtain cylinder samples with 6 mm diameter. To obtain the equilibrium structures the green samples were sintered at 1100°C for 4 h under Ar atmosphere. X-ray diffraction, scanning electron microscopy and energy dispersive spectrometry were used to characterize the as-milled powders and sintered samples. Extended Ti solid solution were found in the Ti-2Mg-22Si-11B and Ti-7-Mg-Si-B powders milled for 20 min and 60 min, respectively, whereas an amorphous halo was produced on Ti-2Mg-22Si-11B powders milled for 420 min. The increase of Mg amount in the starting powder mixture has inhibited the Ti6Si2B formation in the mechanically alloyed and sintered Ti-7Mg-22Si-11B alloy.


2004 ◽  
Vol 379 (1-2) ◽  
pp. 216-221 ◽  
Author(s):  
Nada Stubičar ◽  
Vladimir Bermanec ◽  
Mirko Stubičar ◽  
Darko Popović ◽  
Wolfgang A. Kaysser

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