The Effect of Cooling Rate on the Microstructure and Mechanical Properties of Al-Zn-Mg-Ca Alloy

7XXX aluminum alloy is widely applied to transportation and construction fields due to its high mechanical properties and low density. However, during the preparation process, the stress concentration caused by the defects such as shrinkage cavities derived from the wide solidification range will lead to the premature failure of the alloy. This study replaced Cu in 7XXX alloy with the addition of insoluble element Ca to control the thermal cracking in the casting process, and concluded the effect of casting cooling rate on the microstructure of Al-Zn-Mg-Ca. The contribution of various strengthening mechanisms was quantitatively calculated to analyze the relationship between the casting process and the enhancement of mechanical properties of the alloy. The tensile strength of the ingot obtained by water cooling is 200 MPa higher than that of the ingot obtained by air and furnace cooling. The reason for the improvement in the tensile property is that rapid cooling process promotes the solidification of α-Al and Al₄Ca, and the large amount of solid solution of alloy elements in the base phase. It is also confirmed that the refined secondary phase is the main reason for the performance improvement through the calculation of the strengthening contribution. This study provides an important reference strategy for the preparation of 7XXX aluminum alloys without pressure forging, in order to prevent the thermal cracking and improve the mechanical properties.