Influences of Zn

Mg and Cu on hot cracking behavior and microstructure of 7075 aluminum alloys were investigated by constrained rod casting（CRC）mold.The results demonstrate that hot cracking sensitivity（HCS）is firstly decreased

and then increased to reach the maximum value

and then decreased with increasing in the content of Zn.HCSminis 76.8when the Zn content is 5.44% and HCSmax reaches 141.6when the Zn content is 6.44%.HCSis decreased with Mg content increase

where HCSmin reaches 72 when the Mg content is 3.68%and HCSmaxis 107.2with 1.68% Mg content.HCSis firstly increased and then decreased with Cu content increase.HCSminis 72 when the Cu content is 1.80% and HCSmaxis 101 when the Cu content is 1.50%.The fracture mode of 7075 aluminum alloys is characterized by intergranular fracture.Cracks are propagated along the low melting eutectic microstructure at the grain boundaries.Hot cracking resistance is well with little eutectic microstructure

and hot cracking resistance is worse with a higher eutectic microstructures in condition of solidification shrinkage with poor feeding fed well.Hot cracking resistance is high with eutectic microstructures distributed along crain boundary to be beneficial for feeding.The as-cast microstructure of 7075 aluminum alloys mainly consist ofα-Al andη-MgZn2.