Super Steel For Aerospace And Defense Applications

Scientists from Hong Kong, Beijing and Taiwan have developed a low-cost ‘super steel’ that overcomes the strength-ductility trade off in conventional metallic materials.

AsianScientist (Sept. 4, 2017) – In a study published in the journal Science, scientists from Hong Kong, Beijing and Taiwan have developed a straightforward and inexpensive method to create strong and ductile ‘super steel.’

Aerospace and defence applications require metallic materials with ultra-high strength. However, in some high-loading structural applications, metallic materials must be ductile and have a high toughness to facilitate the precise forming of structural components and to avoid the catastrophic failure of components during service.

Unfortunately, increasing the toughness of the metallic material often leads to a decrease in ductility, which is known as the strength-ductility trade-off. For example, ceramics and amorphous materials have negligible ductility, although they have great hardness and ultra-high strength.

The ability to simultaneously increase both strength and ductility of metallic materials using conventional industrial processing routes is a major challenge for scientists and engineers. In particular, it is very difficult to further improve the ductility of metallic materials when their yield strength is beyond two gigapascals (GPa).

In this study, a team led by Dr. Huang Mingxin from the University of Hong Kong (HKU) developed a Super Steel, also called deformed and partitioned steel (D&P Steel), which addressed the strength-ductility trade-off.

Huang’s group first proposed the deformation mechanism, suggesting that the high dislocation density improves both strength and ductility simultaneously. Dr Luo Haiwen’s group from the University of Science and Technology Beijing then successfully introduced high mobile dislocation density into the steel, and Dr. Yen Hung-wei’s group from the National Taiwan University performed the advanced microstructure characterization.

The chemical composition of D&P steel belongs to the family of medium-manganese steel, containing 10 percent manganese, 0.47 percent carbon, 2 percent aluminum, 0.7 percent vanadium (mass percent), and the remaining of the material consists of iron. The ‘super steel’ has an unprecedented yield strength of 2.2 GPa and uniform elongation of 16 percent.

In addition to its strength and ductility, the material cost of this ‘super steel’ is just one-fifth that of the steel used in current aerospace and defense applications, and it is developed using conventional industrial processing routes, including warm rolling, cold rolling and annealing. This is different from the development of other metallic materials where the fabrication processes involve complex processes and special equipment which are difficult to scale-up. Therefore, it is expected that D&P steel has great potential for industrial mass production.


The article can be found at: He et al. (2017) High Dislocation Density–induced Large Ductility in Deformed and Partitioned Steels.

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Source: University of Hong Kong.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

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