Structural Transformations in Co₈₇B₁₃ and Ni₈₇B₁₃ Alloys during Ball Milling and Influence of Stacking Faults in FCC Co on Amorphous Phase Formation

摘要

A solid state interaction in Co₈₇B₁₃ and Ni₈₇B₁₃ mixtures by high energy ball milling was studied. The methods of XRD and DTA calorimetry analyses were used. It has been established that the formation of Co (B) and Ni (B) solid solutions takes place on the base of fcc structure of both metals. The interaction of B with Co develops in accordance to ??hcp ?Cofcc transformation. Fcc solid solutions Co (B) and Ni (B) can be characterized as interstitial solutions or as mixed-type solutions of substition-interstition. During prolonged milling of Co (B), stacking faults in its lattice are formed, concentration of which goes up to 12.5%. The probability of stacking faults formation in Ni (B) is one order lower. The high defectiveness of Co (B) promotes the amorphous phase formation and the full transformation of Co₈₇B₁₃ alloy into amorphous state is observed after 4200 min of milling. Crystallization of amorphous alloy during heating takes place at temperature above 490 °C, and herewith fcc supersaturated solid solution Co (B) is formed again and the cobalt boride excretion is not observed. Co (B) fcc solid solution formed as a result of mechanical alloying (MA) has decomposed with the Co₂ (C₁₆) tetragonal phase formation at temperature above 560 °C.