The diffusion of platinum, vanadium, and manganese in the Ni3Al phase was investigated under high pressure (figures 21 and 22). Platinum atoms occupied cubic face-centred sites (α) in the L12 structure. Vanadium atoms occupied cubic corner-sites (β). Manganese atoms occupied both sites. The results could be described by:

Mn:     D(m2/s) = 5.9 x 10-1exp[-377(kJ/mol)/RT]

Pt:     D(m2/s) = 7.8 x 10-4exp[-323(kJ/mol)/RT]

V:     D(m2/s) = 3.1 x 10-1exp[-459(kJ/mol)/RT]

The ratios of activation volume, for the diffusion of the atoms, to the molar volume of the Ni3Al phase were 0.75 for Pt, 0.97 to 1.08 for V and 1.01 to 1.03 for Mn. These values meant that the diffusion of platinum was mediated by single vacancies, that of vanadium by divacancies or other complex mechanisms and that of manganese occurred via single vacancies plus other mechanisms.

Diffusion of Platinum, Vanadium and Manganese in Ni3Al Phase under High Pressure. Yamane, T., Hisayuki, K., Yoshida, H., Minamino, Y., Araki, H., Hirao, K.: Journal of Materials Science, 1999, 34[8], 1835-8

Figure 21

Diffusivity of Mn, Pt and V in Ni3Al as a function of pressure

White circles: Mn, white squares: V, black squares: Pt,

white triangles, Pt, black triangles: V. Solid lines: 1573K, dotted lines: 1523K