New Low-Cost Steel Is As Strong As Titanium

 Materials  

Steel is still the predominate choice for many structural applications, however the material suffers from relatively low strength-to-weight ratios. Adding aluminum to steel typically makes it lighter, but extremely brittle. Now researchers have developed a new alloy that allows for the addition of aluminum, without the brittleness.

Hank Reardon, one of the pivotal characters in Ayn Rand's Atlas Shrugged invents a new allow of steel that is stronger, lighter, and cheaper than steel.  Now, researchers in Korea have developed  new form of steel that has the potential to revolutionize the world; although this time, it’s not fiction.

For innumerable uses, steel is still the workhorse material. The researchers at Pohang University of Science and Technology in South Korea have reported what they're calling one of the greatest steel leaps forward of the last few decades: flexible, ultra-strong, lightweight steel.

This new metal has a strength to-weight ratio that matches even our best titanium alloys, however at one tenth the price, and can be made on a small scale with the tools already in place to produce automotive grade steel.

The new material "is 13 percent less dense compared with typical steel, and has almost the same strength-to-weight ratio compared to titanium alloys."

According to Hansoo Kim, the researcher that led the team, "Because of its lightness, our steel may find many applications in automotive and aircraft manufacturing."

The development has been published in Nature.

The key to creating this new super-steel was overcoming a challenge that had hampered materials scientists for years. In the 1970's, researchers discovered that adding aluminum to the mix when creating steel can make an incredibly strong and lightweight metal, but this new steel was unavoidably brittle. You'd have to exert lots of force to reach the limit of its strength, but once you did, the steel would break rather than bend.

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When making the aluminum-steel alloy, they were periodically melding atoms of aluminum and iron together to form a strong, crystalline structure called B2. These veins and pieces of B2 were solid but brittle.

"My original idea was that if I could somehow induce the formation of these B2 crystals, I might be able to disperse them in the steel," he says. The researchers ascertained that if little B2 crystals were forced to separate from each other, then the surrounding composite would protect them from chipping.

Kim and partners invested years formulating and adjusting a technique for high temperature treating and rolling the steel to control when and where B2 crystals formed. The group additionally found that including a small amount of nickel offered much more control over B2 arrangement, as nickel impeded the crystal structure until much higher temperatures.

Kim's group has produced the new metal on a small scale. At the same time before it can be mass-delivered, specialists must stand up to a precarious generation issue.

Presently, steelmakers utilize a silicate layer to cover and ensure large batch steel production runs from oxidation with the air and other contamination in a foundry. This type of silicate can't be used for Kim's steel on the grounds that it tends to react with the cooling aluminum.

For now a few more technical hurdles remain before the team's new steel can reach its full potential. The effort will be justified though: the new material "is 13 percent less dense compared with typical steel, and has almost the same strength-to-weight ratio compared to titanium alloys," according to Kim.

The researchers have already teamed with POSCO, one of the biggest steel makers in the world to see if the new kind of steel can be mass produced.


SOURCE  Popular Mechanics

By 33rd Square

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