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Kinetics of Phase Formation in Mechanically Alloying Ni-Al and Fe-Al Powder Systems
|Ludmila Paritskaya 2, V. V. Bogdanov 1
1. Karazin Kharkov National University, Department of Crystal Physics, Kharkov, Ukraine
Mechanically alloying (MA) Ni-Al multi-layered samples with alternating Ni and Al layers of tens nm thickness and Fe-Al powder systems composed of the spherical Fe particles of tens nm diameter inserted into matrix of fine-grained Fe-Al mixture were used for study the kinetics of intermetallic growth at temperatures 300-600oC. X-ray phase analysis, optical microscopy and SEM were applied for measurement of the volume fraction of new phases and average thickness of intermetallic layers. The kinetics of intermetallic growth was also studied in massive Ni-Al and Fe-Al diffusion couples. The diffusion characteristics for both the MA and massive objects were calculated from the growth kinetics. The phase formation in MA systems begins at much lower temperatures (300oC) compared to massive couples (550oC). Low pressures up to 0.5 kbar accelerated the phase formation in MA powder objects, increasing the phase volume fraction due to increase of phase nucleus density. The mechanism of low-temperature phase formation, based on interdiffusion of both sort atoms along interfaces, phase nucleation at interfaces and their subsequent displacement, is proposed and discussed. Accelerating effect of low pressure is caused by elimination of cavities and other discontinuities at interfaces and as a result the more active phase nucleation at more perfect interfaces.
Presentation: oral at E-MRS Fall Meeting 2004, Symposium I, by Ludmila Paritskaya
See On-line Journal of E-MRS Fall Meeting 2004
Submitted: 2004-04-29 06:58 Revised: 2009-06-08 12:55