A general framework for the mechanical response of metallic glasses during strain-rate-dependent uniaxial compression

Experimental data on compressive strength σ_max versus strain rate for metallic glasses undergoing uniaxial compression shows varying strain rate sensitivity. For some metallic glasses, σ_max decreases with increasing strain rate while for others, σ_max increases with increasing strain rate, and for certain alloys σ_max versus strain rate is nonmonotonic. To understand their strain rate sensitivity, we conduct molecular dynamics simulations of metallic glasses undergoing uniaxial compression at finite strain rates and coupled to heat baths with a range of temperatures T₀ and damping parameters b. In the T₀→0 and b→0 limits, we find that the compressive strength σ_max versus temperature T obeys a “chevron-shaped” scaling relation. In the low strain-rate regime, σ_max decreases linearly with increasing T, whereas σ_max grows as a power-law with decreasing T in the high strain-rate regime. For T₀>0, σ_max(T) deviates from the scaling curve at low strain rates, but σ_max(T) rejoins the scaling curve as the strain rate increases. Enhanced dissipation reduces compression-induced heating, which causes σ_max(T) to deviate from the b→0 scaling behavior for intermediate strain rates, but σ_max(T) converges to the high strain-rate power-law scaling behavior at sufficiently high strain rates. Determining σ_max(T) as a function of b and T₀ provides a general framework for explaining the strain rate sensitivity of metallic glasses under compression.