Using Figure P8.40, explain what the phase diagram is showing when the overall alloy composition is A1–43wt% Ni (below 854°C). Why is there a vertical line at that point in the phase diagram? Verify that the formula for the compound is Al3Ni. What do you call such a compound?
Using Figure P8.40, explain what the phase diagram is showing when the overall alloy composition is Al–43wt% Ni (below 854°C). Why is there a vertical line at that point in the phase diagram. Verify that the formula for the compound is Al3Ni. What do you call such a compound.
Explanation of Solution
Express the number of moles in nickel.
Here, number of moles in nickel is
Express the number of moles in aluminum.
Here, number of moles in aluminum is
Express mole percentage of aluminum.
Express mole percentage of nickel.
Conclusion:
The phase diagram shown in Figure P8.40 is presenting the formation or development of an intermetallic compound between aluminum and nickel as Al–43wt% Ni indicates some substitution between them.
The vertical line at that composition signifies a stoichiometric behavior of the formed intermetallic compound.
Verification of formula:
To verfify the formula for the compound, let the mass of compound be
Write the atomic mass of nickel and aluminum as below:
Substitute
Substitute
Substitute
Substitute
For each nickel atom, there are 3 atoms of aluminum, hence the formula is
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Chapter 8 Solutions
Foundations of Materials Science and Engineering
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