Papers by Keyword: W/Cu

Abstract: A W/Cu system functionally graded material (FGM), which may be used as plasma facing component for fusion reactors, was prepared by inserting W-Cu layers with gradient composition between tungsten and copper alloy plates. W-Cu gradient layers were hot-press sintered from W-Cu powder mixtures added with zinc powder as the sintering aid, whose relative density increased with sintering temperature, reaching a value higher than 96% at 850°C. XRD and SEM measurements showed that the sintered W-Cu gradient layers were the mechanical mixtures of W and Cu. A wholly dense W/Cu system FGM was then obtained at 850°C by hot-press, whose composition and structure changed gradually. The finite element method (FEM) calculation showed that the residual stresses in the W/Cu FGM were effectively reduced as compared with the directly-bonded W/Cu joint.

Abstract: Tungsten has been decided as the plasma facing material (PFM) for some high heat flux regions of the divertor in the International Thermo-Nuclear Experimental Reactors (ITER). In this paper, our efforts concentrated on the functionally gradient W/Cu coating fabricated on the oxygen free copper by atmosphere plasma spraying under the inert gases protection. The functionally gradient W/Cu coatings were designed to relieve the thermal stress during the spraying processes. For comparison, the tungsten coatings were also deposited directly onto the copper substrates by the same technology. XRD, SEM and EDS were applied to identify the phases, morphologies and compositions of these coatings. Tensile tests were performed to measure the bonding strength between the coatings and the substrates. Furthermore, water quenching and high heat loading experiments using a pulse laser beam were also carried out to estimate the thermal shock properties of these coatings.

Abstract: Copper reinforced by tungsten particles has high potential applications in the fields of electronics and electric contacts where high strength accompanied with good electrical conductivity is required. The effects of different scaling parameters (deformed volume, tungsten volume fraction and the tungsten particle size) affect the force needed for the machining of the W/Cu particle reinforced composites. W/Cu composites with different weight percentages of tungsten (80, 70 and 60 wt.%) were tested under compression loading. Different sizes of the compression specimens were tested; the specimen diameter DS was varied to be 1, 2, 4, 6 and 8 mm. The effect of the tungsten particle size was varied to be 10 and 30-m. The compression tests were done at strain rates of 0.1s-1. The experiments were carried out within a temperature range from 20 °C to 800°C. The mechanically tested specimens were metallographically investigated to determine the degree of deformation of the tungsten particles in different specimen geometries. A clear dependence of the flow stress on the volume of the deformed specimens and the tungsten volume fraction was found. This size effects were more obvious with increase of the tungsten volume fraction at lower temperatures. The metallographic investigation was helped to understand the observed size effect of the composites in relation to the volume fraction and the specimen size

Abstract: W/Cu functionally gradient materials (FGMs) are fabricated by a novel process—multi-billet extrusion (MBE). Different W/Cu superfine powders made by mechanical alloying (MA) are used to improve the sinterability of W/Cu compacts. Good quality of three-layer W/Cu extrudes are obtained after confirming the extrusion parameters and the type and the content of binder during extrusion process. The green products are pressureless sintered at the temperature range of 1100-1300 oC for 1 h. W/Cu FGMs with relatively high density and high homogeneous microstructure are attained after sintering at 1200 oC for 1 h. The mechanisms for the enhance of sinterability and improvement of density of the mechanical alloyed (MAed) W-Cu powder products have been discussed. X-ray diffraction and scanning electron microscope are used to identify and observe phase constitution and microstructure, respectively.