March 30, 2020 report
Using chemical boundary engineering to create steel that is strong and flexible without high carbon content
A team of researchers from China, Germany, Japan and the Netherlands has found a way to use chemical boundary engineering to create steel that is strong and flexible without the need for high carbon content. In their paper published in the journal Science Advances, the group describes their technique and how well it worked when tested.
The researchers note that their work was based on the need for lighter high-strength steels for use in transportation and other infrastructure projects. They further note that most high-strength steel, particularly that with ultimate tensile strength, requires a high level of carbon or other expensive elements. In this new effort, the researchers demonstrated that chemical boundary engineering can be used to make high-strength steel without the need for adding carbon or other elements.
Chemical boundary engineering is a technique whereby very small defects in the microstructure of a material, such as steel, lead to the creation of sharp chemical gradients. When used with steel, the result is alternating grains of martensite and austenite, which makes the steel lighter than it would be otherwise. Prior research has shown that creating tiny defects in steel could be used to produce a less expensive hardy steel, but doing so tended to result in damage when it was exposed to strain or heat.
To get around previous problems with using chemical boundary engineering, the researchers used a technique that generated chemical boundaries between austenite grain domains that alternated with small amounts of manganese. Their process involved cold rolling low carbon steel and then subjecting it to a standard austenite reversion treatment for two hours. The steel was then heated to a single-phase austenite region and cooled to ambient temperature. During the cooling stage, the metal settled into different phases until reaching its final state. The team tested their technique by creating samples using chemical boundary engineering and others using the standard technique. They found that their new technique resulted in steel that was stronger without any loss in flexibility compared to the standard method. They also found that testing showed the steel created using the new technique had a strength level beyond 2.0 GPa.
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