Structure And Conductivity Of Cu-Ni-Mo Alloys Designed By The Cluster Model

As one of the most important metallic materials, Cu alloys are widely used for their excellent properties. However, Cu has low strength (230-300MPa), which has limited the application of Cu alloys. Variety of methods can improve the strength of Cu alloys, but all of these will cause decrease of conductivity. To improve the strength of copper alloys as far as possible under precondition of maintaining high conductivity, has been one of the most important topics for material science and research.In order to acquire the combination of high strength and high conductivity, composition design and multi-component alloying are employed. However, a vital problem needs to be solved is how to control the alloy structure in multi-component systems while composition design is undertaken. For example, lots of elements are immiscible with Cu, alloying always cause destabilization of the solid solution, which make it difficult to regulate the structure and conductivity performance of Cu alloys accurately. It is significant to explore the connection of composition, structure and property and establish a thorough theory of composition design.Aiming at alloying indissoluble element Mo in to Cu matrix, a cluster-plus-glue-atom model was adopted. By adding Ni, which is miscible both with Mo and Cu, the structure model was established, which was1Mo atom and12Ni atoms formed an Mo-centered and Ni-surrounded cube-octahedron cluster MoiNi12and distribute in the Cu matrix. Alloys with nominal composition [Moy/y+12Ni12/y+12]xCu100-x were designed and prepared. The structure and properties analysis results showed that:as Mo/Ni=1/12, Mo and Ni would form into Mo1Ni12, and dissolve in the Cu matrix completely. With increasing of the content of alloying elements x, lattice constants of the alloys showed a linear decrease, while the resistivity showed a linear increase. With the change of Mo/Ni, Mo and Ni will dissolve into Cu matrix completely as y≤1. Contrarily, there would be precipitates of Mo in the Cu matrix as y>1. A precise computational formula for resistivity of Cu-Ni-Mo alloys with rich-Cu (≥95at.%) was established as:p=1.80+1.21xNi+1.08xC+0.086xMo, the variables in the formula expressed the atomic percentage of Ni and MoiNi12clusters, as well as precipitated Mo, respectively.The present work demonstrated that using cluster model to design compositions was effective for adding insoluble Mo into Cu alloy in a wide composition region; and achieving quantitative control of the structure and properties of the alloys.