The processing control based on the formation of multilayers and the kinetics of a solid state amorphizing transformation by mechanical alloying(MA) of Co
85Zr
15 is proposed, from which one can optimize the conditions for an efficient and high quality production of amorphous powders using a rotating-arm reaction ball mill with a relatively high rotational speed(R) above 400 rev min
-1. For R=400 and 450 rev min
-1, the use of a higher flow rate of cooling water(C
w) above 830 ?? h
-1 leads to the occurence of a plateau of attrition tempeature, although it is short, prior to an exothermic reaction; this MA process is almost conducive to a two-stage amorphization with Johnson-Mehl-Avrami exponent(n) of n
1=1.4 and n
2=2.6. While, the MA with C
w<150 ?? h
-1 without the plateau shows an apparently single value of n=2.0; this process is denoted as a mixed stage amorphization which includes the formation of a crystalline solid solution. A rotational speed change method consisting of the ball milling by the end of the plateau using R=300 rev min
-1 and an exothermic reaction by MA using of 400<R<500 rev min
-1 leads to the two-stage amorphization even for a lower C
w of 20 ?? h
-1. With increasing R from 300 to 450 rev min
-1, the amorphization rate is found to decrease. The activation energy for the amorphization of Co
85Zr
15 by MA using R=400 rev min
-1 is derived as 2.0±0.5 eV; this value is slightly higher than 1.7 eV for with R=300 rev min
-1.
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