Amorphous alloys surpass E/10 strength limit at extreme strain rates

Area of Science:

• Materials Science
• Mechanical Engineering
• Solid Mechanics

Background:

• Theoretical ideal strength of materials is predicted to be between E/30 and E/10 (Young's modulus).
• Experimental determination of ideal strength in metals has remained challenging.
• Amorphous alloys are of interest for their unique mechanical properties.

Purpose of the Study:

• To investigate the spall strength of Cu50Zr50 amorphous alloy at extreme strain rates.
• To determine if the ideal strength limit of E/10 can be exceeded experimentally.
• To elucidate the failure mechanisms governing material behavior under high strain rates.

Main Methods:

• Laser-induced shock experiments were employed to achieve strain rates exceeding 10^7 s^-1.
• Electron microscopy was used to analyze material microstructure and failure modes.
• Large-scale molecular dynamics simulations were conducted to complement experimental findings.

Main Results:

• Cu50Zr50 amorphous alloy demonstrated a record spall strength of 11.5 GPa, exceeding the E/10 limit (approximately E/6).
• The primary failure mechanism at extreme strain rates was identified as void nucleation and growth.
• A void kinetic model controlled by surface energy explained the observed rate dependence of material strength.

Conclusions:

• Amorphous alloys can achieve exceptionally high elastic limits, surpassing theoretical predictions.
• Understanding void dynamics is crucial for predicting material behavior at extreme strain rates.
• These findings advance the knowledge of mechanical properties in amorphous alloys under dynamic loading.