Research On The Network-like Tungsten Skeleton Reinforced Copper Composite Material For Nuclear Fusion

The heat sink material of nuclear fusion divertor is applied in a comprehensive field environment of super heat flow impact,neutron impact and partial structural pressure,and it needs to have good thermal conductivity and strength.At present,the heat sink materials for divertors are mainly copper-chromium-zirconium alloy and oxide/carbide-reinforced copper alloy.However,due to the problem that thermal conductivity and strength cannot be improved synergistically,its further development is restricted.The tungsten-reinforced copper composite material prepared with the first wall material of the divertor—tungsten as the reinforcing phase,has both the high strength and stability,of tungsten and the high thermal conductivity of copper.However.copper-tungsten composite materials prepared by traditional processes have defects such as difficult structure control,heat conduction,and strength mismatch.To this end.this paper aims at the above problems,starting from the structure design of composite materials,and proposes a new idea of preparing network-shaped tungsten porous skeleton reinforced copper alloy by laser selective melting-infiltration process.The influence of tungsten-copper two-phase content,porous structure of tungsten skeleton and preparation process parameters on the structure,electrical,thermal properties,tensile mechanics and arc ablation properties of composite materials are systematically discussed and analyzed.On this basis.reveal the law of the influence of the networked tungsten skeleton on the properties of composite materials,clarify the strengthening mechanism of the tungsten skeleton reinforced copper-tungsten composite materials,and provide data support for the matching of thermal and mechanical properties of copper-tungsten heat sink materials for nuclear fusion divertors.Research content and results include:1.Based on Ansys finite element simulations,different hole shapes and porosity models are selected.Laser energy is 300 W,and the scanning speed is 450 mm.The selected area is melted and printed into squares with porosities of 68,85.5,71.6,82.1 and 73 Vol.%.A meshed tungsten skeleton with side and body diagonal.The crystal grains appear as equiaxed crystal morphology on the printing plane,and columnar crystal morphology perpendicular to the printing plane.The melt channels on the printing plane are overlapped in a zigzag shape,and the overlap rate of the melt channels is about 40%;perpendicular to the printing plane,the melt channels are superimposed with a "fish scale" appearance.2.The compression curve of the porous tungsten skeleton along the printing direction shows large plastic deformation after compression,the compression strength is 4-79 MPa,and the plastic deformation is not obvious along the curve perpendicular to the printing direction,the compression strength is 3-149 MPa,and the porosity 80%square skeleton has the highest strength.The drooping phenomenon in printing can increase the pressure bearing capacity of the tungsten skeleton along the direction perpendicular to the printing direction.The fracture mechanism is related to the compression direction.The skeletons of various specifications are compressed along the printing direction as quasi-cleavage fractures connected by tearing edges,and typical brittle fractures with cleavage facets perpendicular to the printing direction.3.The porous tungsten skeleton is kept at 1300℃ in H2 atmosphere for 90 minutes,and copper is infiltrated under pressure to prepare copper matrix composites with different content of network tungsten skeleton.The composites are free of impurities,no obvious defects in the micro interface,and uniform density.Above 97.4%.The electrical conductivity is 44.7～-80.3%IACS,and the room temperature thermal conductivity is 233.7～435.0 W/m-K.When the hole shape is square,the electrical conductivity and room temperature/high temperature thermal conductivity of the W-Cu90 Vol.%composite are the best,and the thermal conductivity is still as high as 375 W/m-K at 500℃.4.Conduct tensile tests on tungsten-reinforced copper composites with various pore structures perpendicular to the printing direction.The stress-strain curve has both plastic fracture characteristics and brittle fracture characteristics.The fracture process is divided into tungsten/tungsten fracture(the highest point of strength),tungsten/copper fracture(a stage where the stress drops sharply),and a copper/copper fracture stage(the plastic deformation stage).The fracture is a typical composite morphology of tungsten brittle fracture and copper ductile fracture.When the hole shape is square,it exhibits higher tensile strength,and the strength increases as the W content increases.The square hole W-Cu90 Vol.%composite has the best overall performance,with a tensile strength of 103 MPa and an elongation of 20.9%.5.The first electrical breakdown test of the network-shaped tungsten skeleton reinforced copper-based composite material shows that the breakdown occurs in the copper phase with low melting point and easy to escape,and the copper phase splashing occurs.The skeleton structure affects the ablation resistance of the composite material.After 100 breakdowns,the square hole W-Cu90 Vol.%composite material has shallow ablation pits(the mass loss is only 0.34 mg under 10 kV voltage),indicating that the composite material’s extremely high thermal conductivity and high melting point component tungsten It exerts a synergistic enhancement effect and improves the ablation resistance of the material.