Deformation fingerprints will help researchers identify and design better metallic materials – ScienceDaily

Engineers can now capture and predict the strength of metallic materials subjected to bicycle loading, or fatigue strength, in a matter of hours — not the months or years that current methods take.

In a new study, researchers from the University of Illinois at Urbana-Champaign report that automated high-resolution electron imaging can capture nanoscale deformation events that lead to metal failure and breakage at the origin of metal failure. The new method helps scientists quickly predict the stress strength of any alloy, and design new materials for engineering systems exposed to repeated loading for medical, transportation, safety, energy and environmental applications.

The results of the study, which was led by materials science and engineering professors Jean-Charles Stenville and Marie Charpani, were published in the journal Sciences.

Stress on metals and alloys — such as the repeated bending of a metal paperclip that causes it to break — is the root cause of failure in many engineering systems, Steenville said. Determining the relationship between fatigue strength and microstructure is challenging because metallic materials display complex structures with features ranging from the nanometer to the centimeter scale.

“This multi-scale problem is a long-standing problem because we are trying to observe nanometer-sized scattered events that control the macroscopic properties and can only be captured by examining large regions with high resolution,” Charpani said. “The current method for determining fatigue strength in metals uses conventional mechanical tests that are expensive and time consuming and do not provide a clear picture of the root cause of failure.”

In the current study, the researchers found that the statistical investigation of nanoscale events that appear on a metal’s surface when it deforms can indicate the stress strength of metals. The team is the first to discover this relationship using autocorrelation of high-resolution digital images collected at a scanning electron microscope — a technique that collects and compares a series of images recorded during deformation, Stenville said. The researchers demonstrated this relationship on aluminum, cobalt, copper, iron, nickel, steel and refractory alloys used in a large variety of major engineering applications.

“What is remarkable is that the nanoscale deformation events that appear after one deformation cycle correlate with the fatigue strength that determines the life of the metallic part under a large number of cycles,” Steenville said. “Detecting this association is like accessing a unique deformation fingerprint that can help us quickly predict the fatigue life of metal parts.”

“Designing metal materials with higher tensile strength means materials that are safer, more flexible and more durable,” Charpani said. “This work has social, environmental and economic implications as it sheds light on the fine and nanoscale parameters for tuning materials with long life. I believe this work will set a new paradigm in alloy design.”

This study was conducted in collaboration with researchers from the University of California, Santa Barbara and the University of Poitiers, France.

The Department of Defense, Office of Naval Research, and Illinois Department of Materials Science and Engineering supported this research.

Story source:

Materials Introduction of University of Illinois at Urbana-Champaign, News Desk. Original by Louis Yuxolian. Note: Content can be modified according to style and length.

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