Study On The Interface Mechanical Properties Of Materials And Hydrogen Influence At The Nanoscale

In recent years,with significant demands for light-weighting as a means to reduce energy costs in vehicles and electrical equipment,advanced joining and welding technologies(e.g.,friction stir welding),have been developed and implemented,enabling the joining of lightweight materials(such as aluminum)with other materials with a range of thermophysical properties.The evolution of the microstructure near the composite interface during the joining process is quite complex.The interfaces typically contain microstructures with a certain amount of intermetallics,with higher hardness and strength than the base materials.However,the bond strength of the interface between pure metals and intermetallic compounds is usually lower than the strength of the base materials or compounds.With extensive research in this area,there is a recognition that it is crucial to improve the quality of the interface,reduce defects near the interface,and control the size and shape of the intermetallic phases in the interface region for the interface performance of composite materials.In addition,in response to the call for a low-carbon economy and reduced carbon emissions,hydrogen is being heavily promoted as a green energy source.However,the hydrogen embrittlement effect in materials can lead to a significant decline in mechanical properties,presenting a serious hazard to the safe use of hydrogen.Hydrogen embrittlement occurs due to the diffusion of hydrogen atoms within the material and their interaction with micro-and nanostructures.Interfaces within materials can be used as hydrogen trapping sites to adsorb hydrogen atoms and prevent them from diffusing to vulnerable areas,leading to premature material failure.Therefore,understanding the interaction between hydrogen and interfaces has important implications for designing hydrogen-resistant materials.The interfacial region is often at the nanoscale,it is difficult to directly characterize it using experiments.Moreover,the results obtained from experiments are often a combination of various micro-nano structural effects,making it difficult to quantitatively describe a single structure.The application of molecular dynamics methods allows for the observation of the continuous evolution process of the interfacial microstructure under stress loading,establishing a connection between "composition-structure-performance",and enabling the optimization of actual production processes for the improvement of interfacial mechanical properties through simulation results.Based on this method,this paper studied the composite interfaces of aluminum-copper and phase boundaries/crystal boundaries in steel in a hydrogen environment.The K-Means clustering algorithm was used to combine multi-scale computational results to construct the interfacial metal compound.The effects of annealing temperature on the evolution of the microstructures of aluminum-copper interfaces were evaluated,and the interfacial strength of the aluminum-copper composite array was characterized.The study found that the failure of the aluminum-copper interface occurred on the aluminum-rich side of the interface,and increasing the annealing temperature reduced the defect density and inhibited the generation of nanovoids,thereby improving the interfacial strength.Through simulations of hydrogen adsorption on different pearlite interlayer spacings,it was found that structures with smaller spacings adsorb relatively more hydrogen atoms.The internal grain boundary rotation angle also affects the amount of hydrogen adsorption and exhibits different fracture modes.By constructing different precipitation phase structures to form coherent/incoherent interfaces in steel,it was found that the interfaces capture hydrogen the most strongly.Under different precipitation spacings and hydrogen concentrations,face-centered cubic precipitates formed in the incoherent interface exhibit less hydrogen embrittlement sensitivity.The critical concentration for precipitate capturing hydrogen was determined,and the structure remained stable after capturing hydrogen within this range.Meanwhile,changes in the interaction mechanism between dislocation precipitates were observed under different hydrogen concentrations.