Structural and strains analyses of FeCo/A2o3 elaborated by milling time
YounesAbderrahmane1,2, Zergoug Mourad1,bacha Nacer Eddine2 , Dilmi Nacer2, KHORCHEF Mohammed1 , Amir Mounir1
1Research Center in Industrial Technologies CRTI P.O.Box 64, Cheraga 16014 Algiers, Algeria crti.dz
2Laboratory of surface treatment and Materials, University of Saad Dahleb Blida, Algeria a.younes@crti.dz
Abstract
The effect of milling time of Fe matrix strengthened with 40% wt % Al2o3 during mechanical alloying was examined for nanocomposite alloy at different milling times (5, 15, 20, 30 h), during milling the lattice strain increased from 0.34 to 0.64%, and residual stress increased from 93.024 to 175.104 Gpa, it is due to sever deformation plastic.
Key word: Fe/40Al2o3 nonocomposite, MEB, DRX, EDX 1. Results and discussion
1.1. Morphology
Fig. 1 shows the SEM micrograph for Fe/40Al203nanocomposite powders mechanically alloyed for different milling Times. At the first of milling, the powders are soft and cold welding predominates. Consequently, the particles size increases, Particles shape has become flattened due to cold deformation effects during milling. At the middle of milling, particles have become more rounded in shapes and finer in average size. That's may be because of the predominant processes at this stage are welding and fracturing. Powder particles after 20 h seem with almost the same particle size, but some coarse particles still remain, after 20 h of milling, the balance between the welding and fracture process and a steady-state situation is obtained. It means that the distribution of Al203 particles in the Fe matrix is very uniform at this stage [1-4].
Fig.1. SEM micrographs of Fe-40Al2O3 powders milled for different times
1.2. Structural analysis
Figure 2 shows the x-ray diffraction patterns of Fe /4OAl203milled mixtures for different milling times. All diffraction peaks are identified as either that of Fe or of Al2o3. The X-ray diffraction results clearly show the deformation effects of the milled material after mechanicalmilling. Exactly, in the beginning the increase of the peak widths signifies a reduction of the grain sizes for both Fe and Al2O3, and the displacement of peak signifies accumulation of heterogeneous strain in the materials [5].
But With increasing the milling time to 30 h the intensity of Al203 pick reduced in height due to the reduction of alumina particles and/or the low volume fraction of the Al203 phase
20 30 40 50 60 70 80 90
(012)
20h
15h
5h
Fe oh
Intensity (arb.units)
2θ (°)
30h
Fe Al2o3
(104) (110)
(113) (110)
(024) (116)
(200) (112)
(214)(300) (119) (211)
Fig. 2. XRD of Fe/40 Al2o3 powder nanocomposites produced after different milling times.
Figure3.Show the variation of crystallite size and lattice strain during milling time, the increase of lattice strain and the decrease of the crystallite size during the milling is due to the distortion effect caused by the dislocation in the crystal lattice. The severe plastic deformation provokes a distortion of lattice with a strong density of dislocations [6-9]
Fig. 3. Crystallite size and lattice strain of Fe/40 Al2o3 at different milling time.
0 5 10 15 20 25 30
0 2 4 6 8 10 12 14 16 18 20
Crystallite size Lattice strain
Milling time (h)
Crystallite size (nm)
0.35 0.40 0.45 0.50 0.55 0.60 0.65
Lattice strain (%)
•
Figure4. Show the variation residual stress during milling time, the increase residual stress during the milling is due to the sever deformation plastic effect caused by the mechanical milling.
0 5 10 15 20 25 30 35
80 100 120 140 160 180
Residual stress (Gpa)
milling time (h)
Fig. 4. Residual stress of Fe/40 Al2o3during milling time.
Conclusion
The incorporation of Al2o3 particle into the Fe alloy particles formed a complex composite structure. With increasing milling time, the Al2O3 matrix is always amorphous, the reduction of crystalline size and the increasing of residual stress can be obtained because of the severe plastic deformation during milling.
References
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