Substitutional alloys

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 If two metals are completely miscible with each· other they can form a continuous range of solid solutions. Examples include Cu/Ni, Cu/Au, K/Rb, K/Cs and Rb/Cs. In cases like these, one atom may replace another at random in the lattice. In the Cu/Au case at teftlperatures above 450°C a disordered structure exists (Figure 5.7c), but on slow cooling the more ordered superlattice may be formed (Figure 5.7d). Only a few metals form this type Of continuous solid solution1 and Hume Rothery has shown that for complete miscibility the following three rules should apply.



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