Study on the healing mechanism of nanograin boundary cracks in Al, W, and Ti
Study on the healing mechanism of nanograin boundary cracks in Al, W, and Ti
components must operate in environments with high temper-atures,stresses,irradiation,andhydrogen concentrations[1-6]andmaydevelopnanocracks.Therefore,theirsafeopera-tionrequiresanunderstanding of thestabilizationbehaviorofthesenanocracks athigh temperatures.Alalloyshavea smallthermal neutron absorption cross-section,excellent plasticity,favorable thermal conductivity,and machinability,and arewidelyappliedinnuclearreactorcladdingshells andpressurevessels [1,2].The best candidate metal for the first wall isWowingtoitshighmeltingpoint,high-temperaturestrength.high thermal conductivity, and resistance to irradiation dam-age [3,4].However, the harsh,high-temperature,high-stress,and highly corrosive environment inside reactors requires Aland W alloys with exceptional stability and strength.Al-thoughTiis commonlyused tostore nuclearwaste,itis sus-ceptible to grain boundary (GB)embrittlement [5].In thisstudy, Al, W, and Ti alloys were investigated to understandTi with microstructures that resist deformation,cracking,andfailure (e.g., crack initiation,propagation, and extension)have been successfully developed [1-5]. However, few stud-ing.For example,stress-driven GB migration,which mayoriginate from inhomogeneous stresses,is widely observed innanocrystallinemetals;thisGBmigration canpromotecrackhealing [6].If localized compressive stresses drive crackhealing at the GBs, then concentrated tensile stresses near theGBs may damage the structure inthis vicinity;that is,crackhealing requires a stable structure that can store additionalenergy[4, 5]. The GB crack healing is closely related to GBmigration;therefore,the stability and characteristics of thismigration should be investigated.The complementary pro-cessofhigh-temperature-drivenmicrostructuralevolution canalso promote GB crack healing; the disappearance of GB mi-crocracksisdrivenbyatomicdiffusion after atomsbreakGBcrackbonds athigh temperatures[6-9].However,an accuratemechanical model of alloy crack migration at high tempera-tureshas notyetbeen developed.Todate.design strategiesfor self-healing materials have only been proposed for poly-mers and composites [10].
Metals in advanced nuclear reactors, such as W, often experience microcracks. However, the synergistic effects of high temperature, stress, and specialized structures can improve the self-healing ability of these metals.Microcrack healing is closely related to crack surface conditions. The order and disorder degree of crack surfaceatoms may affect crack stability. In this study, first-principles calculations, ab initio molecular dynamics, andsurface thermodynamic theory were used to investigate the stability of grain boundary (GB) cracks at 0, 293, and373 K. We compared the energy densities, crack attraction energies, and atomic diffusion behaviors of cracksurfaces at P 3GBs with those at P 5GBs. Adsorption on the nanocrack surface determines the critical nanocrack width. It was found that Al P 3(111) nanocracks heal at high temperatures, and this healing behavior isclosely related to the crack surface energy. Meanwhile, the GB cracks of W heal in an orderly manner at 573 and1203 K. BY contrast, the GB cracks of Ti remain unhealed. Finally, a high-temperature nanocrack expansionmodel was developed and used to predict crack behavior under applied stress at different temperatures
Jun Hui 1, Xiao-Yong Zhang,Jia-Peng Chen, Bin Chen,Min Liu, and Biao Wang
冶金技术核反应堆工程
Keywords:GrainboundaryNanocrackSurfacethermodynamictheory
Grain boundary Nanocrack Surface thermodynamic theory
Jun Hui 1, Xiao-Yong Zhang,Jia-Peng Chen, Bin Chen,Min Liu, and Biao Wang.Study on the healing mechanism of nanograin boundary cracks in Al, W, and Ti[EB/OL].(2025-02-03)[2025-08-02].https://chinaxiv.org/abs/202502.00043.点此复制
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