Molecular Dynamics Study Of Al₂Cu/Al Interface In Al-Cu Alloys

Precipitation-hardening mechanisms have been widely applied for the development of high strength and ductile metal-based alloys.Al-based structural alloys that contain Al-based intermetallic precipitates are potential candidates for structural applications at ambient and elevated temperatures because of their lightweight,four times lower density as compared to steel.Through refining the characteristic dimension and distribution of intermetallic precipitates,the ductilit y and strength of Al-based composites can be significantly improved at room temperature.A high volume fraction of thin intermetallic reinforcements can be realized with the help of either rapid solidification with alloying additions or severe plastic deformation?SPD?techniques.However,SPD often leads to destabilization of intermetallic phase,such as the formation of non-equilibrium solid solutions,disordering or amorphization in intermetallic phase.Understanding characters of dislocations and their interactions and roles in mechanical behaviors is essential for developing and advancing the application of Al-based structural alloys in industry.The plate-like shape of Al₂Cu phase particles necessitates a detailed understanding of the interface structure,which governs the structural applications of Al-Cu alloys.In this research,MD simulations are reported for demonstrating a strong dependence of the dislocation structure on the termination at the Al₂Cu/Al heterointerface.Different termination at interfaces exhibit distinct nearest neighbor arrangements,leading to variations in surface across the interface that ultimately dictate the dislocation structure.Among the four possible terminations at Al₂Cu?110?plane,two of them are stable in Al₂Cu/Al heterointerface and the networks of dislocations with different Burgers vectors characterize the feature of these two interfaces.These networks in turn influence the overall mechanical response at the heterointerface.To date,the observed correlation between the interface structure and the termination at the interface has not been recognized for Al-Cu alloys,and offers novel avenues for fine-tuning metal-intermetallic eutectic composites with enhanced properties.Further study of Al₂Cu/Al interface is provided,including interface structure,shear response,quench response,dislocation nucleation at interface,as well as Interface evolution associated with absorption to interstitials at the node of misfit dislocations.MD results show that interface has low shear resistance associated with the gliding of interface misfit dislocations,and nucleation of lattice dislocations is dominated by interface dislocations.Plastic co-deformation is observed when multiple dislocations pile up at interface,which facilitate localized shear in Al₂Cu.The knowledge of slip systems,interface structure and properties,and plastic deformation modes is the essential fundamentals for understanding mechanical behaviors and developing materials modeling tools at high length scales.The creation of vacancies associated with the relatively easy dislocation climb could account for structural instability of Al₂Cu.