关键词: Al-Zn-Mg-Cu合金, 压扭成形, 微观组织, 抗拉强度, 断裂方式

Abstract: Compression and torsion composite forming was used to process an aluminum cup shell. Optical microscope, tensile test and scanning electron microscope were used to study the effects of processing parameters on microstructure, mechanical properties and fracture modes of Al-Zn-Mg-Cu alloy cup shells. The results show that the optimum temperature for processing cup shells is as 400℃ and the microstructure is composed of fine equiaxed grains. Moreover, the tensile strength increases to 430MPa and the strength improves 49.8%. When the deformation temperature is over 300℃,the fracture mode of Al-Zn-Mg-Cu alloy deformed by compression and torsion is of ductile fracture. However, when the deformation temperature is below 300℃,the fracture mode is of brittle fracture. The torsion turns of Al-Zn-Mg-Cu cup shell forming may not be too large(less than 5 turns). When the torsion turn is less than 5 turns, the fracture mode of Al-Zn-Mg-Cu alloy is of ductile fracture. In addition, with the torsion turns increasing, the numbers of dimples on the microscopic fracture surface increase and the depths of dimples are larger. When the torsion turn is more than 5 turns, the fracture mode presents a certain degree of brittle fracture.

Key words: Al-Zn-Mg-Cu alloy, compression and torsion forming, microstructure, tensile strength, fracture mode