Abstract:In order to study the hot fractures in relation to the semi-solid processing, the tensile tests of an extruded 7075 aluminum alloy which is based on Al-Zn-Mg-Cu system were carried out in the high temperature solid and semi-solid states at different strain rates. The results show that the tensile behavior can be divided into three regimes with increasing the liquid fraction. The alloy first behaves in a ductile character, and as the temperature increases, the fracture mechanism changes from ductile to brittle which is determined by both of liquid and solid, and lastly the fracture mechanism is brittle which is totally dominated by liquid. At strain rates of 1×10^-4, 1×10^-3 and 1×10^-2 s^-1, the brittle temperature ranges are 515-526, 519-550 and 540-580 °C, respectively. Two equations which are critical for tensile behavior are proposed.

Key words: Al-Zn-Mg-Cu alloy; mechanical behavior; semi-solid processing; fracture