The hot tearing susceptibility（HTS） of Al-Zn-Mg-Cu alloy semi-solid rheo-die castings was evaluated by the semi-quantitative evaluation method. The fracture morphology and the distribution of cross-section pores were analyzed under different intensification pressures. The results reveal that the H

TS

of the alloy is decreased firstly and then increased with the increase of intensification pressure

and presents the smallest H

TS

value of 15 when the intensification pressure is 87 MPa. With 94 MPa

the H

TS

has the highest value of 27. The pores inside the samples have a strong influence on hot tearing

which is the origination of the hot tearing initiation. The intergranular separation caused by insufficient shrinkage during solidification is the main cause of pores

and the porosity of castings can be effectively reduced by increasing intensification pressures. However

the higher intensification pressure will exert an impact on the solidifying casting

leading to crack and increase of hot tearing.