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ASU Researchers Discover Point on the Way Toward Crack-Resistant Metals

ASU Researchers Discover Point on the Way Toward Crack-Resistant Metals

Sometimes it’s only by looking at things on a smaller scale that scientists can solve the world’s biggest problems.

That’s the approach taken by Arizona State University professor Karl Sieradzki and his team, whose recent study has revealed important new information about the stress-corrosion cracks that form in metal alloy pipes used to transport water, fossil fuels and natural gas — and the alloys used in nuclear power plants and aerospace frameworks. These components are often subject to so-called “season cracking” that can threaten their integrity and present a serious engineering challenge.

The researchers used ultra-high-speed photography to observe how stress-corrosion fractures form in a silver/gold alloy. They found that cracks moved at around 200 meters per second, a speed that would be expected only in a brittle material such as glass. The result is particularly surprising, Sieradzki explained, because gold is one of the most malleable metals known to humans.

The findings shed light on other alloys commonly used in mission-critical applications, such as aluminum alloys (typically aluminum mixed with copper, magnesium, manganese, silicon, tin or zinc), brass (about 67% copper and 33% zinc, though lead may also be added in low concentrations), and stainless steel (steel with at least 10.5% chromium).

The research will likely have significant applications in both industry and public infrastructure, providing a guide for “designing alloys with different microstructures so that the materials are resistant to this type of cracking,” according to Sieradzki.

The research was funded by the Department of Energy’s Basic Energy Science program, and has been published in the prestigious journal Nature Materials under the title “Potential-dependent Dynamic Fracture of Nanoporous Gold” as of June 22. All of Sieradzki’s co-authors, Shaofeng Sun, Xiying Chen and Nilesh Badwe, are also associated with ASU’s materials science and engineering program, either being current graduate students or having earned their doctoral degrees there in the last few years.

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