Molecular dynamics study of the effect of alloying elements and imperfections on linear friction welding of Cu and Ni metals

There are many physical phenomena and properties associated with diffusion in linear friction welding (LFW) process. Many of these phenomena are not observable by known and conventional methods. The molecular dynamics (MD) is an advantageous and practical method to study the diffusion process and atomic behavior of welded materials. In the current research, we used MD simulations to model the LFW process between copper and nickel metals. The effect of defects in the structures and also the addition of alloying elements to the copper structure was also studied. Our findings revealed that the surface and subsurface imperfections in the copper structure were gradually eliminated in the friction stage. In contrast, these imperfections in nickel structure disappeared in the forging stage. Also, we showed that adding alloying elements to copper structure leads to an increase in the amount of the mean square displacement (MSD) of the atoms and the diffusion coefficient in copper.

Nanoscale Assembly of Copper Bearing-Sleeve via Cold-Welding: A Molecular Dynamics Study

A bearing is an important component in contemporary machinery and equipment, whose main function is to support the mechanical rotator, reduce the friction coefficient during its movement, and guarantee the turning accuracy. However, assembly of a nanoscale bearing and sleeve is a challenging process for micro-nano mechanical manufacturers. Hence, we show the cold-welding mechanism of a copper nanobearing-nanosleeve via molecular dynamic simulations. We demonstrate that it is feasible to assemble a bearing and sleeve at the nanoscale to form a stable mechanism. The effect of temperature in the range of 150 to 750 K is investigated. As the temperature rises, the mechanical strength and the weld stress of the welded structures markedly decrease, accompanied by the observation of increasing disorder magnitude. This comparison study is believed to facilitate future mechanical processing and structural nano-assembly of metallic elements for better mechanical performance.