The segregation of impurity elements is known as an important factor leading to abnormal failure of large-scale key structural parts.The segregation degree

segregation position and segregation type of impurity elements such as P

Ca

Zn

Pb

Cu

Fe

Zr and Mn were analyzed for A356.2 aluminum alloy wheel hub by reverse squeeze casting.The results reveal that the rheological behavior of squeeze casting has an important influence on the segregation of impurity elements.Three kinds of interesting segregation are presented as follows:the"channel segregation"along the rheological feeding channel

the "zero rheological segregation" in the non-deformation zone

and the "specific gravity segregation" of calcium and copper.The degree of segregation of these impurity elements can be divided into four grades according to the segregation ratio from low to high.Zinc

plumbum and phosphorus belong to serious segregation elements with the segregation ratio higher than 0.3

which reaches grade 4

while calcium belongs to the heavy segregation element with the segregation ratio of 0.2～0.3

which is grade 3.Meanwhile

the impurity elements such as iron

copper

manganese

zirconium are all light segregation elements with the segregation ratio of 0.1～0.2

which is grade 1 or grade 2.The segregation position of impurity elements is controlled by solidification sequence

rheological state and spatial position.The central position（zero rheological zone）under punch or indenter and local hot spot positions of reverse filling are the accumulation area of k0<1 impurity elements.On the contrary

the farthest position of reverse filling is poor in impurity elements.