To harvest and reuse low-temperature waste heat, we propose and realize an emergent concept—barocaloric thermal batteries based on the large inverse barocaloric effect of ammonium thiocyanate (NH ₄ SCN). Thermal charging is initialized upon pressurization through an order-to-disorder phase transition, and the discharging of 43 J g ⁻¹ takes place at depressurization, which is 11 times more than the input mechanical energy. The thermodynamic equilibrium nature of the pressure-restrained heat-carrying phase guarantees stable long-duration storage. The barocaloric thermal batteries reinforced by their solid microscopic mechanism are expected to substantially advance the ability to take advantage of waste heat.

Compared with traditional alloys, high-entropy alloys have better mechanical properties and corrosion resistance. However, their mechanical properties and microstructural evolution behavior are unclear due to their complex composition. Machine learning has powerful data processing and analysis capabilities, that provides technical advantages for in-depth study of the mechanical properties of high-entropy alloys. Thus, we combined machine learning and molecular dynamics to predict the mechanical properties of FeNiCrCoCu high-entropy alloys. The optimal multiple linear regression machine learning algorithm predicts that the optimal composition is Fe₃₃Ni₃₂Cr₁₁Co₁₁Cu₁₃ high-entropy alloy, with a tensile strength of 28.25 GPa. Furthermore, molecular dynamics is used to verify the predicted mechanical properties of high-entropy alloys, and it is found that the error between the tensile strength predicted by machine learning and the tensile strength obtained by molecular dynamics simulation is within 0.5%. Moreover, the tensile-compression asymmetry of Fe₃₃Ni₃₂Cr₁₁Co₁₁Cu₁₃ high-entropy alloy increased with the increase of temperature and Cu content and the decrease of Fe content. This is due to the increase in stress caused by twinning during compression and the decrease in stress due to dislocation slip during stretching. Interestingly, high-entropy alloy coatings reduce the tensile-compression asymmetry of nickel; this is attributed to the reduced influence of dislocations and twinning at the interface between the high-entropy alloy and the nickel matrix.

Nickel-based single crystal alloys have excellent mechanical properties due to its unique two-phase structure and interface. Therefore, molecular dynamics methods were used to simulate nanoindentation and microstructural evolution. We found the indenter reaction force and hardness of the Ni₃Al phase is the largest. The pop-in event in Ni₃Al phase is more obvious than that in the Ni phase and Ni/Ni₃Al phase. Because lots of dislocations in the Ni₃Al phase break through the barrier of the interface and cut into the Ni phase, while dislocations in the Ni phase only slip inside the Ni phase. Moreover, we found that the position of the starting point of the adhesion force recovery is mainly related to the elastic recovery of the material. The stronger the elastic recovery of the phase, the smaller the depth value corresponding to the starting point of the recovery. We further studied the variation of potential energy with indentation depth and found that the change of wave trough of the load–displacement (P–h) curve is related to stacking fault energy. This study has important theoretical guiding significance for the in-depth understanding and engineering application of the mechanical properties of nickel-based single crystal alloys.

The primary purpose of this paper is to study intergranular and transgranular crack propagation behavior at the grain boundary (GB) of Ni/Ni₃Al by Molecular Dynamics (MD) simulation. Cracks are loaded in tension mode I. The stress–strain curves, the changes of dislocation network, the crack propagation speeds and the changes of interfacial energy are compared with those of two models. The results show that the yield stress of the intergranular crack model is greater than that of the transgranular crack model. It is found that the intergranular crack propagation does not extend along the GB, but the crack extends into the γ′ phase. In addition, the transgranular crack extends at an angle of 45° and the dislocation moves on the slip system {11} [01]. The transgranular crack model breaks completely under a small strain. Moreover, the tranagranular crack propagation results from deformation damage of the model, and its propagation mechanism is shear rupture along the slip plane. The intergranular crack initiates propagation at the most dense position of the slip bands.