CrCoNi CCA

Ultrasonic hardening

This medium-entropy alloy exhibits abnormal ultrasonic hardening, unlike softening in ordinary metals, due to synergistic dislocation multiplication and ordering transitions, offering a new route to tailor mechanical properties.

Xia, Yuanhang · Ma, Xinran · Zhu, Te · Zhao, Pu · Xingzhong, Cao · Chen, Y. · Yan, Jiuchun · Ngan, Alfonso H.W.

Journal of Materials Science and Technology 2026

Specifications

Ultrasonic hardening

{'zh': '52', 'en': '52'} %

Large Cr₂O₃ precipitate size

{'zh': '2.37', 'en': '2.37'} μm

Ultrasonic amplitude (when ordering contribution surpasses Taylor hardening)

{'zh': '11', 'en': '11'} μm

Advantages

Ultrasound hardens

In CrCoNi, increasing ultrasonic amplitude causes dislocation multiplication rather than annihilation, leading to work hardening, opposite to the softening mechanism in ordinary metals.

Forms ordered phases

Ultrasound vibrations trigger disordering-ordering transitions from short- to long-range ordering, producing L1₂ and Cr₂O₃ nano-precipitates and large Cr₂O₃ precipitates that further promote hardening.

Ordering surpasses Taylor hardening

Quantitative analysis shows that at an ultrasound amplitude of 11 μm, the contribution of ordering to hardening surpasses Taylor hardening, revealing the dominant strengthening mechanism.

Applications

• high-entropy alloy components：Directly used as high-entropy alloy components under extreme loads, exploiting ultrasonic hardening to enhance service performance.
• ultrasound-assisted forming：In ultrasound-assisted forming, leverage the abnormal hardening response for localized strengthening or property control.
• extreme-load structural parts：Fabricate structural parts for extreme loads, with ultrasound treatment to enhance deformation resistance.
• mechanical property tailoring：Provide a novel pathway to tailor mechanical properties via ultrasound, enabling precise control of hardening.