High Strength Aluminium Alloys Extrusions - A Review of the Thermo-Mechanical-Process in High Performance Profile Manufacturing

Abstract

High strength aluminium alloys extrusions have successfully been applied for years in transportation industry. High strength alloys are normally understood to be alloys based on the Al-Mg-Zn system (7xxx) with addition of Cu in some cases and of course some micro structural controlling elements as Cr or Zr. The level of strength in the hardened condition (T6) is typical in the range from 320 to 500 MPa. The combination of strength and ductility of extrusions from the 7xxx series alloy gives several advantages in light weight construction and can contribute to lighter body and chassis in automotive. Significant improvements in extrusion speed are realized when the ratio Zn/Mg is increasing this means that alloys with high Zn and low Mg like 7108 and 7003 are favourable. Zr is the most promising element with respect to control the recrystallization phenomena. The fully understanding chemistry and the thermo-mechanical process route in profile based components manufacturing is concluded to be fundamental for high performance products.