Effect of silicon additions on the oxidation of a Ni-6Â at.%Al alloy at 1273Â K

The oxidation of four Ni-xSi-6Al alloys (x = 0, 2, 4 and 6 at.%) has been studied at 1273 K under 0.1 MPa O2. Silicon exerts the third-element effect by reducing the critical Al content needed for the transition from its internal to its external oxidation with respect to Ni-Al alloys. This result is interpreted by extending to ternary alloys Wagner's criterion for the same transition in binary alloys.