Manufacturing The Novel Heat-sink And Structural Materials For Nuclear Fusion Reactors By Adjusting Nano-scale Precipitates

With the increasing demand for energy,as well as the more and more serious environmental problems caused by traditional energy,the development of clean nuclear fusion energy has attracted widespread attentions.The problem of materials has always been a problem that limits the development of fusion reactors,and many current materials can no longer meet the requirements of the next-generation of fusion reactors.For heat-sink materials and structural materials in fusion reactors,insufficient high-temperature structural stability is a major obstacle to their applications.In this paper,several candidate materials that are expected to be used in the next-generation fusion reactors are selected as the research objects,and the role of nano-precipitation phase regulation in micro-crystalline CuCrZr alloy,nano-crystalline Cu-Ta alloy and CoCrFeNi high-entropy alloy is studied respectively.The purpose of nano-precipitated phase regulation is:(1)improve the stability of the precipitated phase itself;(2)regulate the size distribution of the precipitated phase as a gradient distribution.Precipitation phase regulation is achieved by adding trace alloying elements.This article provides certain research ideas and reference significance for the research and development of novel fusion reactor materials.The novel CuCrZrFeTiY alloy for heat-sink materials in divertor is designed and prepared by arc melting,and the microstructure and properties of the alloy are characterized and analyzed.The alloy is treated by solid solution,cold rolling,and aging.The peak aging temperature of the alloy is identified as 500?,at which the tensile strength of the alloy is 541 MPa,and the electrical conductivity is 82%IACS.Long-term annealing experiments exhibit that the alloy has extremely high thermal stability at 450?,and the alloy can maintain high strength even after annealing at 500? for 72 h.The high thermal stability of the novel alloy is mainly contributed to two reasons.One is the high fraction of low-?CSL grain boundaries with low energy existed in the matrix,which forms during the deformation process due to the lowering of the stacking-fault energy(SFE)by the addition of Fe,Ti and Y.Another one is the two kinds of high-density precipitates with bimodal size distribution detected in the matrix,which effectively pinning the dialocations and grain boundaries.After?3 dpa ion irradiation,stacking fault tetrahedrons with an average size of 5 nm and dislocation loops with an average size of 3.5 nm are observed in the alloy.In the current development of the novel heat-sink materials,Cu-10Ta(at.%)alloy has obvious performance advantages.However,the high manufracturing cost limits its wide applications owning to the high content of Ta(24 wt.%).In the present work,the Cu-0.6Ta-0.6Cr and Cu-0.6Ta alloys are prepared by mechanical alloying(MA)and spark plasma sintering(SPS),and the microstructure,tensile properties,softening temperature,and thermal stability of the alloys are characterized.Microstructure analysis indicates that the addition of Cr element not only refines the size of the nano-particles,but also transforms the chemical composition of the nano-particles from Ta to Cr2Ta.The softening temperature of the Cu-0.6Ta-0.6Cr alloy is as high as 1050?(0.97Tm),and the alloy can still maintain 81%of its initial hardness after annealing at 900? for 600 h,while the Cu-0.6Ta alloy can only retain 62%of the initial hardness after annealing at 900?for 300 h.The thermal stability of the Cu-0.6Ta-0.6Cr alloy is highly improved by the addition of Cr.The yield strength of the Cu-0.6Ta-0.6Cr alloy is 481 MPa and the elongation is 14.2%.The yield strength of the Cu-0.6Ta alloy is 331 MPa and the elongation is 13.2%.The addition of Cr improves the strength of the alloy without reducing the ductility of the alloy.Yield behavior exists in the Cu-Ta-Cr alloy while no yield behavior occurs in the Cu-Ta alloy,which is ascribed to the pinning effect of dislocations provided by dislocation locks in the alloy.CoCrFeNi high-entropy alloy is considered as candidate structural materials for fusion reactors due to their corrosion resistance,high plasticity,high radiation resistance,etc.In this paper,the oxide dispersion strengthened CoCrFeNi high-entropy alloy was prepared by MA and SPS methods,and the influences of the introduction of oxides on the structure and properties of the alloy are studied.0.32 vol.%Y2Hf2O7 particles with an average diameter of 6.9 nm are successfully introduced into the matrix,and coherent interfaces are formed between the oxide particles and the matrix.The introduction of oxides refines the grain size and the size of Cr7C3 and Cr2O3 in the matrix,and simultaneously improves the hardness,tensile strength,electrical conductivity and corrosion resistance of the alloy.This work provides an effective way to improve the performance of high-entropy alloys by introducing nano-scale features.