Microalloying of Sc, Ni, and Ce in an advanced Al-Zn-Mg-Cu alloy
- PDF / 1,219,303 Bytes
- 8 Pages / 612 x 792 pts (letter) Page_size
- 70 Downloads / 195 Views
I. INTRODUCTION
THE characteristics that make aluminum a widely used structural material are cost effectiveness, high strength, low density, recyclability, and workability. Moreover, aluminum has been used in aerospace structures for more than 70 years.[1] Recent advances in aluminum alloy/temper development are maintaining aluminum alloys as the materials of choice for future commercial aircraft structures, where there is a need to meet cost and weight-requirement objectives. To address short-term needs while maintaining cost effectiveness, research has also been focused on improvements in traditional ingot-based 2xxx and 7xxx series aluminum alloys and new heat-treatment tempers; examples include the 7150, 7055, and 2524 alloys and the T77 temper. Compared to the higher-cost Al-Li alloys and powder metallurgy (PM) aluminum alloys, materials advances made using the ingot approach tend to be incremental, but provide more cost-effective enhancement of materials performance. That is the main reason why the new super-high-strength ingot metallurgy (IM) 7150 and 7055 alloys have gained wide application in some newly developed aircraft; examples include the C-17, MD-11, and B777, while the use of AlLi alloys and rapidly solidified/PM aluminum alloys in aerospace remains rather limited.[2] To replace the traditional 7xxx Al alloys, such as the USA 7075, Russian B95, and the Chinese LC4 and LC9 alloys (similar to the B95 and 7075 alloys, respectively), which were widely used in Chinese airplanes, the Beijing Institute of Aeronautical Materials has recently developed a new super-high-strength IM/Al-Zn-Mg-Cu alloy (C912). The tensile strength and compressive strength of the C912 alloy are higher than those of the traditional 7xxx aluminum alloys, such as the 7075 and 7178 alloys, and are similar to the YI-LEI WU, Senior Engineer, and CHENGGONG LI, Professor, are with the Beijing Institute of Aeronautical Materials, Beijing 100095, People’s Republic of China. F.H. (SAM) FROES, Director and Professor, and ALEX ALVAREZ, Postdoctoral Research Associate, are with the Institute of Materials and Advanced Processing, University of Idaho, Moscow, ID 838443026. Manuscript submitted April 6, 1998. METALLURGICAL AND MATERIALS TRANSACTIONS A
new Alcoa aluminum alloy 7055 and the Russian alloy B96, which have the highest strengths of the commercial IM/AlZn-Mg-Cu alloys. Aluminum alloys of the 7075 type (Al-Zn-Mg-Cu) are widely used in airframe structures; they provide very high strength and stiffness, but are prone to stress corrosion cracking (SCC), particularly when aged to the near-peak-strength T6 condition.[2,3] Their resistance to SCC can be increased by overaging to the T73 temper, but with a loss of strength. For example, the yield strength of 7075-T73 is about 10 to 15 pct lower than that of 7075-T6.[3] To achieve the objective of obtaining a superior alloy, microalloying elements were added to improve the mechanical and corrosion properties of the C912 alloy. Microalloying technology was originally developed for microalloyed
Data Loading...
