Study on Hot Working, Quenching Sensitivity and Stress Corrosion Cracking Resistance of High Strength Aerospace Aa7000 Series (Al-Zn-Mg-Cu) Alloy

Project Details


In 1936, Sumitomo Metal Ltd. developed a thin plate called "extra super duralumin" which was resistant to stress corrosion cracking(SCC), and was later used on a zero-type fighter aircraft. This is the first time 7000 series (AlZnMgCu) high-strength aluminum alloy (HS-7000) be practical. Since then, in order to meet the application of aerospace structure and components, 7000 series (AlZnMgCu) alloys with higher specific strength, processability, weldability , and SCC resistance have been developed. However, three problems in the manufacturing and using of high strength aerospace Al alloy of 7000 (HS-7000) series, namely (1) low hot working rate (extrusion speed <0.8mm / s), (2) inability to perform on-line heat treatment; and (3) resistant to stress corrosion cracking(SCC); The Al industry and academia are all hope to overcome these problems. In our pre-research found that the low hot working rate was caused by the lower working temperature than (<450 °C). The alloys will be partially melted at the grain boundary, if the working temperature is greater than 450 ° C, resulting in the fragility and the cracking. The reason for the inable to perform on-line solution treatment is due to the high quenching sensitivity of the alloy. When the alloy has high quenching sensitivity, the alloy will not form a supersaturated solid solution, resulting in a decrease in the strength of the alloy. It is necessary to reduce the quenching sensitivity of the alloy, so that a supersaturated solid solution can be obtained at a lower quenching rate. Therefore, this study attempts to alloy design principles, with a variety of enhanced precipitation heat treatment (such as T6, T76, RRA, etc.), by theoretical to explore these two problems, anti-stress corrosion and achieve development to meet the criteria aerospace materials (AMS) specification.As mentioned above, based on the process of the HS-7000 AlZnMgCu series (especially 7075) alloy, a three-year research plan is planned to investigate: (I)high hot working temperatures causing overheating of the HS-7000 series alloys, (II)Quenching sensitivity, and (III)resistance to stress corrosion, can fully present the practical characteristics of this high-strength aluminum alloy. The3-year plan is:1st year: Effect of alloying and heat treatments on working temperature (ie: solution temperature) of wrought HS-7000 alloys2nd year: Effect of alloying and heat treatments on quenching sensitivity of wrought HS-7000 alloys (ie: resulting in inable to quench on-line)3rd year: Developed a wrought HS-7000 experimental alloy that can be deformed at high speed, on-line quenched, and SCC resistant. Based on the practical value and process troubles of the above- mentioned This study is expected to develop the wrought HS-7000 experimental alloy, which can be used to establish its application information for aluminum academia and industry to provide the valuable references.
Effective start/end date1/08/2031/07/21

UN Sustainable Development Goals

In 2015, UN member states agreed to 17 global Sustainable Development Goals (SDGs) to end poverty, protect the planet and ensure prosperity for all. This project contributes towards the following SDG(s):

  • SDG 9 - Industry, Innovation, and Infrastructure
  • SDG 12 - Responsible Consumption and Production
  • SDG 17 - Partnerships for the Goals


  • Al-Zn-Mg-Cu alloy
  • hot working rate
  • processing temperature
  • quench sensitivity
  • stress corrosion


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