Dense Fe-Al-Cr coatings with approximately 50 μm in thickness are successfully prepared on the 1045 carbon steel substrates via a laser cladding process. Proper Cr content(5 at% Cr) will lead to decrease in the melti...Dense Fe-Al-Cr coatings with approximately 50 μm in thickness are successfully prepared on the 1045 carbon steel substrates via a laser cladding process. Proper Cr content(5 at% Cr) will lead to decrease in the melting point, and improves the viscosity of the liquid and the nucleation rate of the molten pool, leading to refining grains of the solidification structure. As a result, the Fe-29 Al-5 Cr laser cladding layer exhibits the best hardness, plasticity properties, and wear resistance at 400 °C. Excessive Cr for the Fe-29 Al-7.5 Cr coating leads to the formation of Cr2 Al in the grain boundaries and thermal vacancies during the solidification process, resulting in inferior mechanical properties and poor tribological behavior.展开更多
Sapphire, belonging to hexagonal crystal system, is typically anisotropic which makes it direction-sensitive. To research the effects of growth directions on properties of sapphire, c-[0001] seed（c-sapphire） and a-[...Sapphire, belonging to hexagonal crystal system, is typically anisotropic which makes it direction-sensitive. To research the effects of growth directions on properties of sapphire, c-[0001] seed（c-sapphire） and a-[11-20] seed（a-sapphire） were used to prepare sapphire by edge-defined film-fed growth（EFG） method. The samples were analyzed through lattice integrity, dislocation and corrosion performance by double-crystal XRD, OM, AFM, SEM and EDX. It was shown that the lattice integrities of two growth-direction crystals were both well due to the small FWHM values. While the average densities of dislocation in c-sapphire and a-sapphire were 9.2×103 and 3.9×103 cm-2 respectively, the energy of dislocation in c-sapphire was lower than that in a-sapphire. During Strong Phosphoric Acid（SPA） etching, the surface of c-sapphire basically kept smooth but in a-sapphire there were many point-like corrosion pits where aluminum and oxygen atoms lost by 2：1. Our work means that it will be promising for growing c-[0001] seed sapphire by EFG if aided by parameter optimization.展开更多
基金Funded by National Natural Science Foundation of China(No.51371097)Six Talent Peaks(2015)Project of Jiangsu Province(No.YPC16005-PT)the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘Dense Fe-Al-Cr coatings with approximately 50 μm in thickness are successfully prepared on the 1045 carbon steel substrates via a laser cladding process. Proper Cr content(5 at% Cr) will lead to decrease in the melting point, and improves the viscosity of the liquid and the nucleation rate of the molten pool, leading to refining grains of the solidification structure. As a result, the Fe-29 Al-5 Cr laser cladding layer exhibits the best hardness, plasticity properties, and wear resistance at 400 °C. Excessive Cr for the Fe-29 Al-7.5 Cr coating leads to the formation of Cr2 Al in the grain boundaries and thermal vacancies during the solidification process, resulting in inferior mechanical properties and poor tribological behavior.
基金supported by Open Fund of Key Laboratory of Material Preparation and Protection for Harsh Environment(Nanjing University of Aeronautics and Astronautics)Ministry of Industry and Information Technology(56XCA17006)the Innovation Fund of NUAA(Nanjing University of Aeronautics and Astronautics)(kfjj20180602)。
基金Funded by the Special Fund of Jiangsu Province for the Transformation of Scientific and Technological Achievements(No.BA2012049)the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘Sapphire, belonging to hexagonal crystal system, is typically anisotropic which makes it direction-sensitive. To research the effects of growth directions on properties of sapphire, c-[0001] seed（c-sapphire） and a-[11-20] seed（a-sapphire） were used to prepare sapphire by edge-defined film-fed growth（EFG） method. The samples were analyzed through lattice integrity, dislocation and corrosion performance by double-crystal XRD, OM, AFM, SEM and EDX. It was shown that the lattice integrities of two growth-direction crystals were both well due to the small FWHM values. While the average densities of dislocation in c-sapphire and a-sapphire were 9.2×103 and 3.9×103 cm-2 respectively, the energy of dislocation in c-sapphire was lower than that in a-sapphire. During Strong Phosphoric Acid（SPA） etching, the surface of c-sapphire basically kept smooth but in a-sapphire there were many point-like corrosion pits where aluminum and oxygen atoms lost by 2：1. Our work means that it will be promising for growing c-[0001] seed sapphire by EFG if aided by parameter optimization.
基金National Natural Science Foundation of China(51975286)Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX18_0272)+1 种基金Opening Project of Jiangsu Key Laboratory of Advanced Metallic MaterialsPriority Academic Program Development of Jiangsu Higher Education Institution。
