Solid-state diffusion reaction was studied at 838 to 898K by using bulk diffusion couples. It was found that ZrAl3 formed in the diffusion zone in all of the couples, with a planar morphology. A second layer of Zr2Al3 also formed in the diffusion zone, at and above 873K. The formation of ZrAl3 as the first phase was explained on the basis of the modified effective heat of formation model. The driving forces for the formation of Zr2Al3 and ZrAl2 at the Zr/ZrAl3 interface were evaluated. The appearance of Zr2Al3, in preference to ZrAl2, at higher temperatures was attributed to the higher driving force for its formation at the Zr/ZrAl3 interface. The temperature dependence of the growth of the ZrAl3 phase layer was determined. The activation energy for the growth of ZrAl3 was 188.2kJ/mol, and the pre-exponential factor was 2.9 x 104m/s1/2.

Intermetallics in the Zr–Al Diffusion Zone. A.Laik, K.Bhanumurthy, G.B.Kale: Intermetallics, 2004, 12[1], 69-74