EFFECT OF PREALLOYING OF METALLOID COMPONENTS ON AMORPHIZATION OF NI-SI-B POWDERS BY MECHANICAL ALLOYING

From experimental results for preparation of the Ni75Si8B17 alloy by mechanical alloying (MA) of different starting materials, using a high energy ball mill, including prealloyed materials such as Ni-B and Ni-Si alloys, it was shown that prealloying effects of metalloid components B and Si in starting materials used clearly appear during MA and in particular, employing boron in the form of Ni-B alloy markedly promotes solid-state reactions in milled powder products. The MA powders of Ni75Si8B17 prepared from a powder mixture of elemental nickel metal and M-B and Ni-Si alloys after 720 ks of milling showed a halo pattern characteristic of amorphous materials in X-ray diffraction. They also showed a sharp exothermic reaction in the thermogram of differential scanning calorimetry (DSC), which can be attributed to the crystallization of the amorphous phase formed in the MA powders. The crystallization enthalpy (-4.0 kJ/mol) and the crystallization temperature (770 K), measured by DSC, of the MA powders of Ni,,Si,B,, thus prepared were comparable to those of melt-quenched, amorphous ribbons of the same composition as the present system.