Zinc Equivalent Coefficient in Brass
The structure of complex brass can be calculated from the "zinc equivalent coefficient" of the elements added to the brass. Since a small amount of other alloying elements are added to the copper-zinc alloy, it is usually only to move the α/(α+β) phase region in the Cu-Zn state diagram to the left or right. Therefore, the structure of special brass is usually equivalent to the structure of ordinary brass which increases or decreases the zinc content. For example, the structure after adding 1% silicon to the Cu-Zn alloy corresponds to an alloy structure in which 10% zinc is added to the Cu-Zn alloy. Therefore, the "zinc equivalent" of silicon is 10. The "zinc equivalent coefficient" of silicon is the largest, and the α/(α+β) phase boundary in the Cu-Zn system is significantly shifted to the copper side, that is, the α phase region is strongly reduced. The "zinc equivalent coefficient" of nickel is a negative value, that is, the alpha phase region is enlarged.
The α phase and β phase in special brass are multi-component complex solid solution, and the strengthening effect is large, while the α and β phases in ordinary brass are simple Cu-Zn solid solution, and the strengthening effect is low. Although the zinc equivalent is equivalent, the properties of the multiple solid solution are not the same as those of the simple binary solid solution. Therefore, a small amount of multi-component strengthening is a way to improve the properties of the alloy.