Processing Control for Solid State Amorphization of CoZr by Reaction Ball Milling (メカニカルアロイング・反応焼結における組織制御・磁性流体<特集>) -- (メカニカルアロイング)
スポンサーリンク
概要
- 論文の詳細を見る
The processing control based on the formation of multilayers and the kinetics of a solid state amorphizing transformation by mechanical alloying(MA) of Co<SUB>85</SUB>Zr<SUB>15</SUB> 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<SUP>-1</SUP>. For R=400 and 450 rev min<SUP>-1</SUP>, the use of a higher flow rate of cooling water(C<SUB>w</SUB>) above 830 ?? h<SUP>-1</SUP> 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<SUB>1</SUB>=1.4 and n<SUB>2</SUB>=2.6. While, the MA with C<SUB>w</SUB><150 ?? h<SUP>-1</SUP> 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<SUP>-1</SUP> and an exothermic reaction by MA using of 400<R<500 rev min<SUP>-1</SUP> leads to the two-stage amorphization even for a lower C<SUB>w</SUB> of 20 ?? h<SUP>-1</SUP>. With increasing R from 300 to 450 rev min<SUP>-1</SUP>, the amorphization rate is found to decrease. The activation energy for the amorphization of Co<SUB>85</SUB>Zr<SUB>15</SUB> by MA using R=400 rev min<SUP>-1</SUP> is derived as 2.0±0.5 eV; this value is slightly higher than 1.7 eV for with R=300 rev min<SUP>-1</SUP>.
- 社団法人 粉体粉末冶金協会の論文