| The thermal stability for the amorphous (Fe_(l-x)Co_x)_(80)B_(20) alloys has been studied systematically through DTA, X-ray diffraction pattern and the electrical resistance change response to temperature and time variations. The results obtained are as follows; 1) The crystallization temperature of amorphous (Fe_(l-x)Co_x)_(80)B_(20) alloy is independent of the concentration of Co and it is about 710˚K. 2) The crystallization process of amorphous (Fe_(l-x)Co_x)_(80)B_(20) alloy occurs in two steps; In the composition range of 0.1≤x≤0.5, amorphous (Fe_(l-x)Co_x)_(80)B_(20)→α phase (Fe, Co; bcc)＋Fe₃B(bct) →α phase (Fe, Co; bcc)＋Fe₂B(fct)＋Co₂B(fct), and in the composition of x = 0.6 amorphous (Fe_(l-x)Co_x)_(80)B_(20)→α phase (Fe, Co; bcc) ＋Fe₃B(bct)＋Co₃B(fct) →αphase (Fe, Co; bcc)＋Fe₂B(fct)＋Co₂B(fct), and in the composition of x = 0.7 amorphous (Fe_(l-x)Co_x)_(80)B_(20)→αphase (Fe, Co; bcc) ＋Co₃B(fco)→αphase (Fe, Co; bcc)＋Fe₂B(fct)＋Co₂B(fct) 3) The crystallization of amorphous (Fe_(l-x)Co_x)_(80)B_(20) is the diffusion-controlled nucleation and growth process, and the crystallization activation energy of amorphous (Fe_(l-x)Co_x)_(80)B_(20) alloy is independent of the composition of Co and it is about 70㎉/mole. |
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