DISORDERING AND AMORPHIZATION OF L12-TYPE ALLOYS BY MECHANICAL ATTRITION

X-ray diffraction patterns obtained during the grinding of Ni3Ge and Ni3Al alloys which at equilibrium exhibit the L1(2) ordered fcc structures show the emergence of a nanocrystalline structure and transformation to the disordered fcc form but little amorphization. Furthermore, the non-L1(2) Al2Pt alloy which also has a more strongly negative heat of mixing is easier to amorphize than the Ni3Ge and Ni3Al with L1(2) superstructure. This is in contrast to the Zr3Al Compound (also L1(2)-type) for which a short milling time is sufficient for obtaining complete amorphization. Variations in the aptitudes toward amorphization of the three L1(2)-type alloys under ball-milling conditions are attributed in part to the differences in the lattice stability terms of their disordered fcc phases.