History of the Development of Extra Super Duralumin and Future Research Issues of Al-Zn-Mg Alloys.

Almost 85 years have passed since the development of Al-Zn-Mg-Cu Extra Super Duralumin in Japan in 1936. This alloy was developed by Dr. Igarashi in response to the Japanese Navy's order to Sumitomo to develop an alloy with tensile strength of 588 MPa (60 kg/mm²) or higher, exceeding Alcoa's super duralumin 24S. This alloy was then adopted for use in the Zero fighter. Based on this alloy, Alcoa's 75S was developed in 1943. This paper describes the history of the development of Extra Super Duralumin, starting with Duralumin. The paper also discusses the issues that are considered important for the future development of the aluminum alloys based on the historical review and our study. One is the relationship between quench sensitivity and age-hardening properties of AlZnMg alloys and the second is the occurrence of shear fracture in the Al-Zn-Mg-(Cu)-Zr alloys. This is the points to be noted in the development of high strength and high toughness Al-Zn-Mg-Cu alloys. [ABSTRACT FROM AUTHOR]