The challenge of achieving both hardness and ductility in metals has long been a major focus of technological development. Recently, Korean researchers at Korea University have developed a new technology for ultra-high-strength maraging medium-entropy alloys through identifying a novel mechanism that enables dynamic phase transformation of precipitates.

In designing ultra-high-strength alloys, two typical strengthening methods are utilized. The first method involves rapidly cooling the metal to create a hard microstructure, called Martensite, following high-temperature maintenance, while the second method involves precipitating elements that exist in a supersaturated state due to rapid cooling through appropriate heat treatment to create particles. While these methods are effective in increasing strength, they reduce ductility and lead to decreased resistance to extreme loads. Maraging alloys exhibit both of these strengthening mechanisms, making them extremely hard and tough, but the trade-off between strength and ductility remains a challenge even with precise alloy design and traditional strengthening mechanisms.

To address this issue and achieve high ductility while maintaining ultra-high strength up to 2 gigapascals, the research team used high-entropy alloys with high degrees of freedom in element type and content selection. They explored a method of increasing ductility while maintaining high strength by using intermetallic compounds that induce dynamic structural changes during the metal deformation process as precipitates. The team used advanced alloy design methods, including first-principles calculations and thermodynamic simulations, to theoretically identify intermetallic compounds that undergo dynamic phase transformation as precipitates. They were then able to experimentally confirm the new mechanism.

Prof. Sohn noted, "This study suggests that enhancing strength using precipitation particles in the development of ultra-high-strength structural materials does not necessarily require a significant sacrifice in ductility. The proposed method is expected to be utilized for specific purposes in fields such as aerospace, space, defense, and power generation, where extreme environments and severe loads are endured and gradually increasing strength is demanded."

The precipitation behaviors and dynamic phase transformations enabling outstanding mechanical performance

[Reference] Chung et al. (2023) “Doubled strength and ductility via maraging effect and dynamic precipitate transformation in ultrastrong medium-entropy alloy”

Nature Communications, https://doi.org/10.1038/s41467-023-35863-z 

[Main Author] Hyung Chung(Korea University), Won Seok Choi(SK Innovation), Seok Su Sohn(Korea University)

* Contact : Professor Seok Su Sohn (sssohn@korea.ac.kr)