Study on nanocrystallization and amorphization in Fe–Cr–Mo–B–P–Si–C system during mechanical alloying

Mechanism of Mechanically Induced Nanocrystallization of Amorphous FINEMET Ribbons During Milling

“…Prolonging the milling time to 45 minutes causes, the peaks of the crystalline phases become sharper and shift to lower angles indicating more dissolved atoms in Fe lattice. [7,15] The morphology of the powders after different milling periods is shown in Figure 2. It is clear that the particle size distributions become more homogeneous and the particle shapes more regular with increasing milling time.…”

“…By substituting these parameters in Eq. [7] and considering the average value for elastic energy, DG(T, P) * could be expressed as DGðT; PÞ Ã ¼ 10:4929  10 8 À3613 þ P  1000ðÀ2:16Þ ½ 2 kJ=mol:…”

“…During milling of the crystalline materials, the internal energy of system increases continuously due to the introduction of significant volume fraction of structural defects such as disordered grain boundaries, vacancies, and dislocations making amorphization more prone to occur. [5][6][7] Suryanarayana et al [6] have stated two conditions needed to be satisfied for the formation of an amorphous phase: first, the large negative heat of mixing in the amorphous state which provides the thermodynamic driving force for the occurrence of the reaction and second, different diffusion coefficient of the primary constituents into each other and also in the amorphous phase. [6] Although solid state amorphization of FINEMETtype alloys has been extensively studied by many researchers, [7][8][9][10][11] very few investigations have been reported which explore the opposite; the crystallization transformation of amorphous FINEMET ribbons induced by mechanical milling.…”

“…[5][6][7] Suryanarayana et al [6] have stated two conditions needed to be satisfied for the formation of an amorphous phase: first, the large negative heat of mixing in the amorphous state which provides the thermodynamic driving force for the occurrence of the reaction and second, different diffusion coefficient of the primary constituents into each other and also in the amorphous phase. [6] Although solid state amorphization of FINEMETtype alloys has been extensively studied by many researchers, [7][8][9][10][11] very few investigations have been reported which explore the opposite; the crystallization transformation of amorphous FINEMET ribbons induced by mechanical milling. While the effect of the temperature increase during mechanical milling has been considered in some reports, [12,13] the effects of the high local pressure generated by the impacts (estimated in the range of 2 to 6 GPa [14] ) on the crystallization of amorphous FINEMET alloys have not been studied yet.…”

Microstructural characterization and amorphous phase formation in Co40Fe22Ta8B30 powders produced by mechanical alloying

“…Their excellent properties are attributed to the absence of the atomic long range order and crystalline defects like dislocations and grain boundaries [1][2][3][4][5].…”