Temperature-dependent deformation of methane hydrate within phase boundary

Natural gas hydrates preserve a huge amount of methane, yet are highly sensitive to temperature fluctuations, especially under conditions close to the phase equilibrium boundary. The influence of temperature on bulk hydrate thermodynamic stability has been broadly quantified, whereas mechanical behavior, particularly at the microscale, has been rarely reported. we employed nanoindentation within the phase equilibrium boundary to investigate the mechanical response of methane hydrate, observing pronounced temperature-dependent stress relaxation during load-holding and significant energy dissipation during unloading. Molecular dynamic simulations of the nanoindentation process support these findings and reveal that stress-induced melting is the underlying mechanism for both the stress relaxation and energy dissipation. Further analysis of energy dissipation reveals that the mechanical behavior of methane hydrate is governed by competing mechanisms across different supercooling regimes. Under large supercooling (exceeding 37.72 K), deformation is predominantly elastoplasticity. Under the supercooling range of 0–37.72 K, the mechanical response is dominated by a mixed mechanism in which both stress-induced phase transition and elastoplasticity coexist. Notably, along the phase equilibrium boundary, deformation becomes entirely governed by phase transition with no elastoplasticity behavior. These findings highlight that across a wide range of temperatures within the phase equilibrium boundary, the mechanical behavior of methane hydrate is inevitably influenced by stress-induced melting, suggesting that mechanical loading under such conditions primarily promotes phase transition while also playing a key role in controlling mechanical deformation.