Question 1
Which of the following is TRUE concerning substitutional alloys?
◦ Titanium carbide is an example of a substitutional alloy.
◦ The metals forming a substitutional alloy must have very different electronegativities.
◦ The metals involved must have similar radii.
◦ One type of metal atom is inserted in between the metal atoms in the initial crystal structure of the other metal.
◦ The two metals must be miscible over the entire composition range.
Question 2
Why can't chromium and nickel form a miscible solid solution over the entire composition range?
◦ The lever rule says that these two metals can't coexist in an alloy.
◦ The octahedral holes in the chromium crystal are not large enough to accommodate the nickel.
◦ The tetrahedral holes in the nickel crystal are not large enough to accommodate the chromium.
◦ The two metals crystallize into different cubic structures in their pure forms.
◦ Chromium atoms can only fit inside tetrahedral holes, which are not present in the structure of pure nickel.
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