Fabication And Properties Of Tungsten-fibre-net Reinforced Tungsten Composites

With the development and application of nuclear fusion reactors,the plasma facing material must be have good toughness,high strength,high recrystallization temperature and excellent radiation resistance.Tungsten alloys are the most favored candidate for the plasma-facing material of nuclear fusion reactors.But pure tungsten has inherent embrittlement,such as low temperature embrittlement,recrystallization embrittlement and radiation embrittlement,which limits structural applications of the first wall plasma-facing materials.Therefore,improve the brittleness of tungsten based materials is one of the most problems.Tungsten fibre toughen pure tungsten by external toughening is considered one of the most effective methods.The strain energy is dissipated by pull-out,interface debonding,necking and frictional sliding at engineered fibre/matrix interface.So tungsten fibre can improve the brittleness of tungsten based materials.In this paper,we prepared tungsten/tungsten fibre composites by powder metallurgy,and studied the physical properties.The main results are as follow:1.The tungsten fibres were knitted into round network by hand-woven.The tungsten fibre nets with the diameter of 20mm or 60mm were tightly and not loosed,and the distance of fibre was several ten microns.The nets and tungsten powder were mixed,and ensure that all tungsten fibre arranged in the same direction.In the prepared samples,the diatence of fibre nets was 100-200?m.2.The W500/Wf100?W500/Wf150?W200/Wf100 composites were prepared by Spark Plasma Sintering,the mass fraction of tungsten fibre were 23.94%?17.4%and 22.3%,respectively.The tensile ductility occurred at 500? in W500/Wf100 composites,which 200? lower than pure tungsten,and the toughness was 22%.The tensile ductility was 21%in W500/Wf150 composites at 600? tested temperature,and the tensile strength was 410MPa.The matrix grain size in W200/Wf100 composites was nao-micro,which had high hardness and low temperature toughness.The Vickers hardness of matrix and fibre was 612 and 616 HV0.2,respectively.What's more,the composites show toughness at 250?,even lower than other two tungsten alloys.In W/Wf composites sintered by SPS,tungsten fibre nets were distributed evenly,and the fibre had a good touch with the matrix.The fibre was toughened pure tungsten by cracking,pull-out and necking.3.The W500/Wf150 composites were prepared by Hot Pressing Sintering,the mass fraction of tungsten fibre were 10.5%and the density of sample was 95.1%.The tensile strength was 420MPa when tested at 600?,and the enlongation was about 20%.In W/Wf Composites sintered by HP,tungsten fibre nets were distributed evenly,and the fibre had a good touch with the matrix.At the same time,the toughening behavior of fibre was the same with SPSed samples.4.The W500/Wf150 composites with 99.8%density were prepared by cold rolling.The tensile strength was 800MPa tested at 300?,and the tougheness occurred at 400?,200-300? lower than pure tungsten.The grains in the matrix were changed to spindle-shaped,and the aspect ratio of grains in fibre was 8.37.Cold rolling made high dislocation and defect density,lead to the proportion of grains with small misorientation angles(?<10°)in fibre,matrix of near the fibre and far away from the fibre were 31.5%,72.7%and 78.3%,respectively.