anda Copper 
Sd Taig 
Eh mig in 
Me tan 3 
‘b, 
Fig.2 Microstructure of hot pressed three layer (a) and six layer Cu-W gradient material (b) 
Electron beam tests on Cu-W gradient have been performed to investigate the effect of 
thermal shock induced surface modification. Materials have absorbed about 2,5MJ/m?, which is 
55% of deposited energy. In Tab 1. materials properties are summarized after exposing to electron 
beam. 
Tab.1 Properties of electron beam treated samples 
nique (a), and — : 5 _ 
Sample (FGM Ds | W-layer ''Thickness Percent of! Electrical | Thermal 
‘Type W particle preparation of W-layer damaged resistivity conductivity 
of 330MPa- (um) (mm) „area (Qm) |(WmK) | 
a of the Cu-W IA [6-layer |22 {HP (600MPa) ı 0,7 111,2 7,62*10° 10,939 ! 
ere at 1150°C, 'B |6-layer [12 [CP(1,13GPa) 10,7 10,1 8,41*10° [0,839 
jr gradient C 22 | HP(G00M Pa) $2 ‘18,9 1510 
» produced by D i 3-layer |12 CP(850Mpa) '2 | Total 15,7 4,58*10 
| damage eG 
WOCHEN *HP-hot pressing, CP-cold pressing 
Kal Plasma disruption caused the sudden evaporation of a thin layer of tungsten. However, most 
ad a of the ablated material would be re-deposited back to the surface [8]. The area of damaged region 
varied with the composite structure and properties of external W layer. Fig.3 shows surface 
WE modification of sample A and D, with maximal and minimal damaged area, respectively. In sample 
A damaged area is located in impact region only, without damaging of the outer region. In sample 
D spallation of the whole sample surface is observed. Due to formation of the liquid phase in W 
layer, the most critical erosion mechanism is associated with instabilities of the molten layer. 
Plasma pressure, and possibly gravitational forces may result in rapid extraction of the melted 
Co layer [9]. More information about interaction plasma-materials are presented in Fig.4. Obviously, 
on 20“ there exists a tendency for the formation of deep cracks perpendicular to the sample surface, which 
< amelie are oriented parallel to each other (Fig 4a). No cracks were observed in the interface region in all 
sd ph composite structures. Redeposition of solidified droplets of molten metal (Fig 4b) causes additional 
! Sen! porosity on the surface. Intergranular crack propagation was observed (Fig 4c). 
r. Yoo 3 Due to analogy between electrical and thermal diffusivity, thermal conductivity for all 
sample have been calculated by Wiedermann-Franz law. Investigation of thermal behavior of Cu-W 
graded material (Tab. 1), show that 6-layer samples have much better thermal conductivity. Smaller 
damaged surface area is the consequence of better thermal conductivity. Sample A has slightly 
higher values of thermal conductivity due to higher density of W layer (92% of theoretical density), 
compared to density of sample B (82% of theoretical density). 
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