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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. == Derivation == Suppose an alloy at an equilibrium temperature ''T'' consists of ''c'' wt% (weight percentage) of element B. Suppose also that at temperature ''T'' the alloy consists of two phases, α and β, for which the α consists of ''a'' wt% B, and β consists of ''b'' wt% B. Let the weight of the α phase in the alloy be so that the weight of the β phase is , where is the total weight of the alloy. By definition, then, the total weight of element B in the α phase is , while the total weight of element B in the β phase is . Together these two quantities sum to the total weight of element B in the alloy, which is given by . Therefore : By rearranging, one finds that : This final quantity is the weight percentage of the α phase in the alloy. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「lever rule」の詳細全文を読む スポンサード リンク
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