Supersonic Speeds Shatter Metal Strength Rules

Groundbreaking Cornell research upends 70-year-old metallurgy principles

Apr. 11, 2026 at 7:05am

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A bold, abstract painting in soft colors depicting intricate geometric shapes, waveforms, and spirals, conceptually representing the complex scientific forces at play in the study of metal deformation at supersonic speeds.Groundbreaking research challenges long-held assumptions about metal strength, revealing how extreme speeds can shatter the rules of material science.Wheatland Today

Contrary to long-held beliefs, new research from Cornell University has found that when metals are deformed at supersonic speeds, smaller grains actually make them softer, not stronger. This discovery could revolutionize the design of everything from bulletproof vests to spacecraft.

Why it matters

The study challenges the Hall-Petch effect, a foundational principle of metallurgy since the 1950s. If the findings hold true, it could force a major rethinking of how engineers approach material design and manufacturing for high-impact applications.

The details

Led by assistant professor Mostafa Hassani and doctoral student Laura Wu, the Cornell team used laser-induced microprojectile impact testing to propel microscopic particles at metal samples faster than the speed of sound. Surprisingly, their results showed that larger-grained copper samples proved harder and more impact-resistant than smaller-grained ones, contradicting the Hall-Petch effect. The researchers attribute this to a phenomenon called dislocation-phonon drag, where defects in the metal interact with vibrating atoms at ultra-high speeds, weakening smaller grains.

  • The study was published on January 9, 2026 in Physical Review Letters.
  • The research was supported by the National Science Foundation and the Army Research Office.

The players

Mostafa Hassani

An assistant professor at Cornell University who led the research team.

Laura Wu

A doctoral student at Cornell University who co-authored the study.

Physical Review Letters

The scientific journal that published the groundbreaking research.

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What they’re saying

“We expected a straightforward confirmation. Instead, we uncovered something entirely unexpected.”

— Mostafa Hassani, Assistant Professor, Cornell University

“We were stunned. We double-checked everything, but the data was clear.”

— Laura Wu, Doctoral Student, Cornell University

What’s next

The researchers plan to further test their findings on other metals and alloys to determine if the reversal of the Hall-Petch effect is truly universal under extreme conditions.

The takeaway

This research not only rewrites textbooks, but also opens up new possibilities for designing materials that can withstand extreme impacts, from lightweight armor to debris-resistant spacecraft. The potential applications are vast, especially in the field of additive manufacturing.