Novel insights into interstitial atoms synergistically augmenting the mechanical characteristics of NiCo coating and interfacial strength with Cu substrate

Precisely delineating the intrinsic correlation between the mechanical properties of the coating bulk and interface is crucial for the fabrication and application of advanced coatings. In this investigation, we garnered insights into the synergistic enhancement mechanisms of interstitial atoms on the mechanical attributes of NiCobulk and NiCo/Cu interface, encompassing factors such as atomic bonding and electron distribution through first-principle calculations. The results showed that the incorporation of interstitial atoms is beneficial for augmenting Young's modulus of the NiCo alloy in the [111] direction while concurrently facilitating the conversion of weak ionic bonds into strong covalent interactions, which enhances the elastic properties, hardness, and tensile strength of the alloy. Moreover, the fortifying impact of the interstitial atoms on the NiCo-bulk was seamlessly translated into enhancements in NiCoX/Cu interface properties. Specifically, under external forces, the deformation of the interface was constrained by the NiCo-bulk. During tensile testing, interstitial atoms mitigated the impact of strain on the atomic bond lengths and charge density, ensuring sturdy local bonding at the interface and ultimately varying the degrees of improvement in interfacial tensile strength. Essentially, the amplification of the NiCo-bulk by interstitial atoms emerged as a pivotal factor that directly enhanced the mechanical properties of the NiCo/Cu interface.