Transient oxidation of Single-Crystal β-NiAl

The Physical and Mechanical Metallurgy of NiAl

“…The oxidation resistance of NiAI alloys is due to the easy formation and slow growth rate of protective Al 2O3 scales. At low temperatures, y-Al 2O3 is the commonly observed oxide (Doychak, Smialek, and Mitchell 1989;Brumm and Grabke 1992). At temperatures near 1200 K, O-Al 2O3 appears to be the predominant oxide in mature scales, but at higher temperatures, a-Al 2O3 is formed (Rybicki and Smialek 1989).…”

“…Several studies have concentrated on the mechanisms of oxidation in NiAI in terms of mass transport phenomenon. Examination of tracer diffusion data (Young and DeWit 1986) and scale morphologies (Doychak, Smialek, and Mitchell 1989) indicates that the transition oxides grow primarily by outward cation diffusion. At higher temperatures, the mature a-Al203 oxide also grows initially by outward Al diffusion (Prescott et al 1992) with the contribution of inward oxygen transport increasing during later stages of oxidation because of a strong influence from short circuit diffusion paths (Jedlinski and Borchardt 1991;Nicolas-Chaubet, Huntz, and Millot 1991).…”

Al2O3scale development on iron aluminides

“…On -NiAl, Doychak et al [2] studied the oxidation of (001), (012), (011) and (111) single crystals containing 0.1wt% Zr using plan-view TEM specimens. The major oxide On all alloy orientations, the scale formed epitaxially, whereas the degree of preferred orientation decreased with oxidation time.…”

Strains in Thermally Growing Alumina Films Measured In-Situ Using Synchrotron X-Rays

“…When an Al 2 O 3 forming alloy is oxidized, a transition alumina film generally develops first, and it later transforms to the thermally most stable α-Al 2 O 3 . These transition aluminas have been identified to be either the θ [13][14][15][16] or the γ phase [17][18][19]. They grow 1-2 orders of magnitude faster than α-Al 2 O 3 [14,20], and the growth is dominated by aluminum outward transport [21].…”