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The deformation modes of single crystal NiAl deformed in compression in the range 77 to 1000 O K were found to be dependent on orientation and temperature. The preferred slip direction was confirmed as (OOl), but this may be constrained geometrically to allow kinking, or slip in (111) or (011) directions, depending on temperature. When (001) slip occurred, the slip plane was invariably { 110) at 77 O K but was dependent on orientation a t higher temperatures. The slip planes were also sensitive to temperature when slip occurred in other directions. The von Mises criterion for polycrystalline ductility can be satisfied by combinations of the observed slip systems.On trouvb que le mode de dbformation de monocristaux NiAl, deformbs par compression entre 77 et 1000 O K depend de l'orientation ainsi que de la tempbrature. On confirme que la direction pdferentielle de gliasement est

Fig. 14. Distortion in cupnous oxide at the CuO-Cu,O interface after oxidation at 940 OC for 2 hrs. Replica X 4100 {Etched lightly in FeCl, + HCl solution and Au-Pd shadowed) Courtesy of Pergamon Press has been used to estimate the effect of various elements at a concentration of about 0.4 wt 010 on the adherence of scales on iron (13, 14). The results fall into four groups; those that form mixed oxide scales with wiistite either spalled or were weakly adherent; those on the more noble metal alloys were nearly comparable with pure iron, but copper and tin had a detrimental effect. Scales containing As, Sb and P were weakly adherent but left a thin adherent scale layer on the metal surface. Cobalt and niobium had no effect. Surface enrichment in the subscale layer was very noticeable in certain cases, particularly with As. This effect has been reported by Vodopivec and his colle-agues (15, 16) and could be very significant considering the ubiquitous nature of this element. I t is probably responsible for the thin ,,white" layers with low carbon content seen in early hammer-welded iron artifacts.