Relationship between composition, structure, and mechanical properties of a condensed composite of copper–tungsten system

Abstract

For a copper-tungsten microlayered composite material for electrical contact applications, which is prepared by electron-beam evaporation-condensation, the changes in its structure, conductivity, hardness, and mechanical properties in tension at room temperature and elevated temperatures are studied versus the tungsten content and heat treatment conditions. New morphological features of the condensed composite and the related changes in the material properties have been revealed. The conditions for the formation of structural defects and their influence on mechanical properties and fracture behavior of the material in tensile tests have been investigated. A relationship has been established between the tungsten content of the composite, its structure, strength, and hardness.Introduction. The present-day composite materials (CM) based on tungsten and copper were developed in the second half of the 20th century. These pseudoalloys which are usually prepared by powder metallurgy (PM) methods have been widely accepted for electrical, structural, and special applications. Despite a long-term experience of using these materials, the research efforts in this field are still pursued, which is due to an extension of technological potentialities for controlling the CM composition, dispersion, distribution of the refractory component inside the product, etc. [1][2][3][4][5][6][7]. Considering that electrical and thermal conductivities of tungsten are lower than those of pure copper, there arises the necessity to search for technological possibilities of producing combined products. In these products the Cu-W composite is used only for facing the contact components of electrical switchgear, which significantly changes the components' functionalities. The implementation of the combined product design presents some difficulties for the quality of the copper body/composite facing interface has to be thoroughly inspected. These difficulties as well as the necessity to separately prepare the facing and the contact component can be in some cases eliminated owing to the use of a technology with provides microlayer gradient composites.Fundamentally new possibilities for the production of these materials have arisen owing to the development of electron-bean units and the elaboration of a process of high-rate electron-beam evaporation of the CM components from separate water-cooled crucibles with subsequent layer-by-layer condensation of the mixed vapor flow onto a metal substrate [8][9][10][11][12]. The main and undeniable benefits offered by the electron-beam technology which provides new-generation electrical-contact composites based on copper and refractory metals are as follows:(i) the possibility of atomic-and molecular-level mixing of vapor flows of substances that have a limited mutual dissolubility and producing composite materials and coatings with a preset structure, chemical composition, physical-mechanical properties and performance, which cannot be achieved by any other available methods; 426 0039-2316/11/4304-0426 (ii) ...

Modern composite materials for switching and welding equipment. Information 2. Application of high-rate vacuum evaporation methods for manufacturing electric contacts and electrodes

“…Cu-(0.05-0.1)(Zr, Y)-W CM. Structure, physico-chemical, mechanical and service properties of composites with up to 50 % W content are described in detail in [47][48][49][50]. Cu-and W-based composite materials are traditionally used as high-current electric contacts in oil circuit-breakers.…”