Aluminum-matrix boron carbide (B4Cp/Al) is a kind of neutron absorbing material widely used in nuclear spent fuel storage. In order to improve the tensile property of B4Cp/Al composites, a new type of nano-Al2O3 parti...Aluminum-matrix boron carbide (B4Cp/Al) is a kind of neutron absorbing material widely used in nuclear spent fuel storage. In order to improve the tensile property of B4Cp/Al composites, a new type of nano-Al2O3 particle (Al2O3np) reinforced B4Cp/Al + Al2O3np composites were prepared by powder metallurgy method. The Monte Carlo particle transport program (MCNP) was used to determine the influence of Al2O3np on the thermal neutron absorptivity of composites. The universal material testing machine and scanning electron microscope (SEM) were used to study the mechanical properties, microstructure and fracture morphology of B4Cp/Al composites. The results indicated that the neutron absorption properties of B4Cp/Al composites were not affected by the addition of nano-Al2O3 particles in the range of 1 wt%-15 wt%. The addition of Al2O3np can obviously reduce the grain size of B4Cp/Al matrix metals thus improve the tensile strength of the composites. The addition threshold of Al2O3np is about 2.5 wt%. Both B4Cp and Al2O3np change the fracture characteristics of the composites from toughness to brittleness, and the latter is more important.展开更多
Mg-based alloys are potential candidate materials for a fabrication of lightweight boron carbide based composites through a reactive melt infiltration approach. In this paper, the effect of a mechanical purification o...Mg-based alloys are potential candidate materials for a fabrication of lightweight boron carbide based composites through a reactive melt infiltration approach. In this paper, the effect of a mechanical purification of molten AZ91 alloy’s surface on its wettability with polycrystalline B_(4)C is experimentally evaluated for the first time. For this purpose, sessile drop experiments were performed under the same operating conditions(700℃/5 min;Ar atmosphere), by using both the classical contact heating(CH) and the improved capillary purification(CP) procedure. It was found that the evolution of contact angle values was strongly influenced by the applied procedure. In particular, by using the classical CH procedure, the presence of a native oxide layer on the metal surface hinders the observations of melting process, resulting in a misleading conclusion that the system is non-wettable. Contrarily, during the wetting test performed by applying the CP procedure, the surface oxide layer was mechanically removed by squeezing the molten AZ91 alloy through a capillary. Accordingly, the oxide-free AZ91 drop with a regular and spherical shape was successfully obtained and dispensed on the B_(4)C substrate. A reliable contact angle value of θ =83° was measured at the AZ91/B_(4)C triple line at 700 ℃, which in turn proves that B_(4)C is wetted by the liquid AZ91 alloy. In contradiction to the literature, these good wetting conditions were assisted by a non-reactive wetting mechanism occurring at the AZ91/B_(4)C interface. To succeed in the fabrication of AZ91/B_(4)C composites by liquid metal infiltration, such experimental observations make it reasonable to expect a spontaneous infiltration process exclusively driven by capillarity, which in turn increases the efficiency of the process by the absence of reaction products that could be a potentially detrimental factor.展开更多
B4Cp/6061Al composites have become important structural and functional materials and can be fabricated by powder metallurgy and subsequent hot rolling. In this work, the effects of the hot-pressing temperature on micr...B4Cp/6061Al composites have become important structural and functional materials and can be fabricated by powder metallurgy and subsequent hot rolling. In this work, the effects of the hot-pressing temperature on microstructures and mechanical behaviors of the B4Cp/6061Al composites were investigated. The results showed that compared with the T4 heat treated B4Cp/6061Al composite hot pressed at 560℃, the yield strength and failure strain of the composites hot pressed at 580℃ were increased to 235 MPa and 18.4%, respectively. This was associated with the interface bonding strength between the B4C particles and the matrix. However, the reaction products, identified to be MgAl2O4 phases, were detected in the composites hot pressed at 600℃. The formation of the MgAl2O4 phases resulted in the Mg depletion, thus reducing the yield strength to 203.5 MPa after the T4 heat treatment due to the effect of the solid solution strengthening being weakened. In addition, the variation of hardness and electrical conductivity was mainly related to the Mg content in the matrix. Based on the as-rolled microstructures observed by SEM, SR-μCT and fracture surfaces, the deformation schematic diagram was depicted to reflect the tensile deformation process of the composites.展开更多
基金Funded by Natural National Science Foundation of China(NSFC)(No.11305149)National High-Tech R&D Program(863 Program)(No.2013AA030704)。
文摘Aluminum-matrix boron carbide (B4Cp/Al) is a kind of neutron absorbing material widely used in nuclear spent fuel storage. In order to improve the tensile property of B4Cp/Al composites, a new type of nano-Al2O3 particle (Al2O3np) reinforced B4Cp/Al + Al2O3np composites were prepared by powder metallurgy method. The Monte Carlo particle transport program (MCNP) was used to determine the influence of Al2O3np on the thermal neutron absorptivity of composites. The universal material testing machine and scanning electron microscope (SEM) were used to study the mechanical properties, microstructure and fracture morphology of B4Cp/Al composites. The results indicated that the neutron absorption properties of B4Cp/Al composites were not affected by the addition of nano-Al2O3 particles in the range of 1 wt%-15 wt%. The addition of Al2O3np can obviously reduce the grain size of B4Cp/Al matrix metals thus improve the tensile strength of the composites. The addition threshold of Al2O3np is about 2.5 wt%. Both B4Cp and Al2O3np change the fracture characteristics of the composites from toughness to brittleness, and the latter is more important.
基金the financial support given by the National Science Centre (NCN) in Poland,under the project MINIATURA 2, No. 2018/02/X/ST8/03044 in2019–2020。
文摘Mg-based alloys are potential candidate materials for a fabrication of lightweight boron carbide based composites through a reactive melt infiltration approach. In this paper, the effect of a mechanical purification of molten AZ91 alloy’s surface on its wettability with polycrystalline B_(4)C is experimentally evaluated for the first time. For this purpose, sessile drop experiments were performed under the same operating conditions(700℃/5 min;Ar atmosphere), by using both the classical contact heating(CH) and the improved capillary purification(CP) procedure. It was found that the evolution of contact angle values was strongly influenced by the applied procedure. In particular, by using the classical CH procedure, the presence of a native oxide layer on the metal surface hinders the observations of melting process, resulting in a misleading conclusion that the system is non-wettable. Contrarily, during the wetting test performed by applying the CP procedure, the surface oxide layer was mechanically removed by squeezing the molten AZ91 alloy through a capillary. Accordingly, the oxide-free AZ91 drop with a regular and spherical shape was successfully obtained and dispensed on the B_(4)C substrate. A reliable contact angle value of θ =83° was measured at the AZ91/B_(4)C triple line at 700 ℃, which in turn proves that B_(4)C is wetted by the liquid AZ91 alloy. In contradiction to the literature, these good wetting conditions were assisted by a non-reactive wetting mechanism occurring at the AZ91/B_(4)C interface. To succeed in the fabrication of AZ91/B_(4)C composites by liquid metal infiltration, such experimental observations make it reasonable to expect a spontaneous infiltration process exclusively driven by capillarity, which in turn increases the efficiency of the process by the absence of reaction products that could be a potentially detrimental factor.
基金financial support of National Key Research and Development Program of China (No. 2017YFA0403803)the National Natural Science Foundation of China (Nos.51525401, 51774065, 51601028, 51690163)+1 种基金Dalian Support Plan for Innovation of High-level Talents (Top and Leading Talents, 2015R013)fundamental research funds for the central universities (Nos. DUT18RC(3)042, DUT17RC(3)108)
文摘B4Cp/6061Al composites have become important structural and functional materials and can be fabricated by powder metallurgy and subsequent hot rolling. In this work, the effects of the hot-pressing temperature on microstructures and mechanical behaviors of the B4Cp/6061Al composites were investigated. The results showed that compared with the T4 heat treated B4Cp/6061Al composite hot pressed at 560℃, the yield strength and failure strain of the composites hot pressed at 580℃ were increased to 235 MPa and 18.4%, respectively. This was associated with the interface bonding strength between the B4C particles and the matrix. However, the reaction products, identified to be MgAl2O4 phases, were detected in the composites hot pressed at 600℃. The formation of the MgAl2O4 phases resulted in the Mg depletion, thus reducing the yield strength to 203.5 MPa after the T4 heat treatment due to the effect of the solid solution strengthening being weakened. In addition, the variation of hardness and electrical conductivity was mainly related to the Mg content in the matrix. Based on the as-rolled microstructures observed by SEM, SR-μCT and fracture surfaces, the deformation schematic diagram was depicted to reflect the tensile deformation process of the composites.
