An alloying element refers to a metal or nonmetallic element that is intentionally added or retained in the matrix metal to give the metal a certain property.

Impurity：Metal or non-metallic elements present in the metal but not intentionally added or retained.

The basic principles for grade nameing

1) The grade name of international four digits system can be directly quoted.

2) The wrought aluminum, aluminum,and aluminum alloy,which is not named as an international four-digit system grade,shall be a four-character gardename(but the experimental aluminum and aluminum alloy’s garde namde is  with prefix X plus four character).

3)In terms of the grade name of  aluminum alloy,the first, third and fourth digits of the four-character system are Arabic numerals,and the second is English capital letters(except C, I, L, N, O, P, Q, Z).The first digit of the grade name represents the group of aluminum and aluminum alloy.In addition to modified aluminum alloy,the aluminum alloy group maily defined by the main alloying elements(for instance 6XXX by Mg2Si).The second letter in the grade name indicates the modification of the original pure aluminum or aluminum alloy,and the last two digits are used to mark the different aluminum alloys in the same group or the purity of the aluminum.