The lever rule is a tool used to determine weight percentages of each phase of a binary equilibrium phase diagram. It is used to determine the percent weight of liquid and solid phases for a given binary composition and temperature that is between the liquidus and solidus.
In an alloy with two phases, α and β, which themselves contain two elements, A and B, the lever rule states that the weight percentage of the α phase is
where
- a is the weight percentage of element B in the α phase
- b is the weight percentage of element B in the β phase
- c is the weight percentage of element B in the entire alloy
all at some fixed temperature.
Read more about Lever Rule: Derivation
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