Model alloys

Fig.6. The B2(110) surface average (solid lines) and sub-lattice (dotted lines) concentrations of the segregant in AB model alloy as a function of reduced temperature calculated in the FCEM approximation for different segregation/order factors r (indicated near the plots). The difference in sub-lattice concentrations corresponds to the surface LRO parameter that vanishes at the surface transition temperature Tg that coincides with the bulk transition temperature T independently of r.

Fig.9. Surface Induced Order at the LI2(100) surface in AB3 model alloy calculated in the FCEM approximation for r=l. p= and 2 correspond to the first and second under-layer, respectively.

Figure 13.3 shows the calculated potential energy surfaces for the oxidation of a C atom and the attachment of a C atom to a carbon nucleation center (C-C bond formation) on the (111) surface of Ni and the (111) surface of a Sn/Ni model alloy. The carbon nucleation center was modeled as a chain of carbon atoms on Ni(lll) organized in the geometry corresponding to the lowest energy. The DFT calculations indicated that on Ni(lll) the potential energy surfaces associated with the C-C and C-0 bond formation are very similar to each other. On the other hand. Fig. 13.3 also shows that on the Sn/Ni model alloy the overall activation barrier for the oxidation of carbon atoms is much lower than the overall activation barrier... 

Liao, C.-M., and Wei, R. P., Galvanic Coupling of Model Alloys to Aluminum - A Foundation for Understanding Particle-Induced Pitting in Aluminum Alloys, Electrochimica Acta, 45 (1999), 881-888. 

Crystalline solids Ionic solids Molecular solids Atomic solids Electron sea model Alloy... 

Idrac, G. Mankowski, G. Thompson, P. Skeldon, C. Blanc, Y. Kihn, Galvanic corrosion of aluminum-copper model alloys, Electrochim. Acta 52 (2007) 7626—7633. 

Figure 98. Densification behavior of model alloys with 30 vol.-% binder with and without Ti addition (after [340]).

Tak] Takahashi, H., Ohnuki, S., Kinoshita, H., Nakahigashi, S., Effect of Alloying Elements on Phase Stabihty in Neutron-Irradiated Fe-Cr-Mn Model Alloys , J. Nucl. Mater., 629—632, 179-181 (1991) (Experimental, Phase Diagram, 13)... 

Bonl] Bonade, R., Spaetig, R, Schaeublin, R., Victoria, M., Plastic Flow of Martensitic Model Alloys , Mater. Sci. Eng. A, 387-389, 16-21 (2004) (Phase Relations, Experimental, Meehan. Prop., 18)... 

Fe or Ni ion irradiation with energies of a few MeV is mostly used for studies of radiation damage of RPV steels. Previous studies have provided information on the effects of Cu, Mn and other elements, carbides, dose rate and tensile stress on hardness, matrix damage evolution and solute cluster formation in model alloys and commercial steels (e.g. Fujii and Fukuya, 2005 Murakami et al., 2009). These data provide clear evidence of the effects of various metallurgical parameters on hardening and microstructural evolution in Fe-based alloys and RPV steels, although these data cannot be directly or quantitatively correlated to data from neutron-irradiated materials. 

Auger P, Pareige P, Akamatsu M and Van Deysen J-C (1994), Microstructural characterization of atom clusters in irradiated pressure vessel steels and model alloys , J Nucl Mater, 211,194-201. 

Watanabe H, Masaki S, Masubuchi S, Yoshida N and Dohi K (2013), Effects of Mn addition on dislocation loop formation in A533B and model alloys, J Nucl Mater, 436,268-275. 

Distribution of Cu atoms from simulated ECOPoSAP data from a Fe-0.25wt%Cu model alloy (20 x 20 x 50 nm sub-volume). In (a) well-defined clusters are clearly visible. In (b) the distribution of Cu atoms is not random, but it is difficult to discern individual clusters. 

PA studies on RPV steels are important because they have the potential to provide information on matrix defects. However, since interpretation of the data from complex commercial steels is difficult, many studies have focused on model alloys. In Section 9.11.1 we include a brief review of a selection of PA data from the literature, focusing first on model alloys and then on steels. It is shown that, in combination with post-irradiation annealing and other microstructural techniques, positron annihilation techniques can help elucidate the nature of the positron traps. 

Valo et found strong evidence for vacancy clusters in irradiated model alloys. They used both positron hfetime and PALA to study ternary alloys irradiated to 4.6 x lO n/cm. The lifetime measurements indicated... 

In addition to studying model alloys, Valo etalso examined various steels irradiated to a fluence of 2.5 x 10 n/cml In contrast to the model alloys, no evidence was found for vacancy clusters. No simple explanation for the difference in irradiation response was suggested however, it was postulated that higher alloying and impurity concentrations in the RPV model alloys may be important. 

The TTS model predictions and the IVAR Aa data plotted against the square root of fluence for a 0.4wt%Cu-1.25wt%Ni model alloy and an A302B steel containing 0.14wt%Cu and 0.2wt%Ni. ... 

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