Diffusion in Metals, Intermetallics, Silicides, Quasicrystals and Metallic Glasses
Ni- and Fe-diffusion in B2-ordered ternary intermetallic compounds.
Intermetallic compounds with a B2 ordered structure on the basis of binary Ni-Al or ternary (Ni,Fe)-Al alloys are
attractive materials for high-temperature application. It is known from literature that the addition of Fe to NiAl
improves the mechanical properties of binary NiAl. The composition
Ni40Fe10Al50reveals the largest creep resistance among the ternary B2
NiFeAl phases. This observation was suggested to correspond to a minimum in the self- diffusivity in this
compound. As direct tracer diffusion data were missing in this ternary system, we investigated Ni and also Fe
diffusion first of all in the mentioned ternary alloy and in alloys on a quasi-binary section with
Al = 50 at %, which lies completely in the B2 phase region of the NiFeAl ternary phase
diagram. The study of Ni and Fe diffusion as a function of the Fe content x in the
Ni50-xFexAl50 ternary alloys is very promising to yield valuable
information in view of similarities and differences in the defect structure and diffusion behaviour of the terminal
binary NiAl and FeAl alloys, which have already been investigated extensively. As a result, Ni diffusion and the
corresponding activation enthalpies show a significantly non-monotonous composition dependence. For the
alloy with 10 at % Fe no minimum in DNi was observed. Thus there is no direct
correlation between the creep resistivity and bulk diffusion. The dominating diffusion mechanism in all ternary
alloys corresponds with the tripledefect mechanism in agreement with other observations from literature.
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