The 6351 wrought aluminum alloy and K2TiF6-CaF2-LiCl components were selected as raw materials to fabricate in situ Al3Ti particulate reinforced aluminum alloy at 720℃via direct melt reaction method with electromagne...The 6351 wrought aluminum alloy and K2TiF6-CaF2-LiCl components were selected as raw materials to fabricate in situ Al3Ti particulate reinforced aluminum alloy at 720℃via direct melt reaction method with electromagnetic stirring(EMS).CaF2 and LiCl acted as fluxes to lower the reaction temperature of the system.It is shown that the electromagnetic stirring and fluxes accelerate the emulsion process of K2TiF6.Optical microscopy,scanning electron microscopy,transmission electron microscopy and energy dispersive spectrum were utilized to analyze the microstructure and components of composites.Compared to composites fabricated without EMS and fluxes,the sizes of endogenetic Al3Ti are refined from 10-15μm to 2-4μm,which are often accompanied with silicon element.The morphology of Al3Ti or Al3TiSi0.22 exhibits triangle,quadrilateral and other clumpy patterns. Because of the Ca elements from CaF2,the sizes of Mg2Si decrease from 8-10μm to 1-2μm due to the formation of Ca2Si.展开更多
B4C particulate-reinforced 6061A1 composite was fabricated by powder metallurgy method. The as-rolled composite possesses high tensile strength which is comparable to that of the peak-aged 6061A1 alloy. More important...B4C particulate-reinforced 6061A1 composite was fabricated by powder metallurgy method. The as-rolled composite possesses high tensile strength which is comparable to that of the peak-aged 6061A1 alloy. More importantly, the microstructures and mechanical properties are thermally stable during long-term holding at elevated temperature (400℃). The microstructual contributions to the strength of the composite were discussed. Transmission electron microscopy (TEM) analysis indicates that the in-situ formed reinforcement Mg(Al)B2, as products of the interfacial reactions between B4C and the aluminum matrix, show not only good resistance to thermal coarsening but also strong pinning effect to the grain boundaries in the alloy matrix.展开更多
In cooling process of Fe-Cr-Al alloy oxidized at 1 300 ℃, the effect of cooling speed and exposure time on oxide spalled area fraction and successive variety of the spalled region were studied by investigating evolve...In cooling process of Fe-Cr-Al alloy oxidized at 1 300 ℃, the effect of cooling speed and exposure time on oxide spalled area fraction and successive variety of the spalled region were studied by investigating evolvement of the thermally grown oxide using in-situ CCD monitoring technique. The results showed that oxide spallation can be restrained by controlling cooling speed and the critical temperature drop of spallation initiation which is closely related to the oxide thickness or exposure time, and the spallation process of a little region may be described in more detail as two routes： from the oxide/substrate interface micro-decohesion, micro-buckles, buckle spreading, buckle crack to spallation and from the interface micro-decohesion, micro-buckles, buckle crack and spallation to the residual oxide decohesion and spallation.展开更多
基金Project(2007AA03Z548)supported by the National High-Tech Research and Development Program of ChinaProject(207038)supported by the Key Program of Ministry of Education of China+3 种基金Project(06-D-021)supported by the Talents Peak in Six Key Fields of Jiangsu Province in ChinaProject(07JDG084)supported by the Technical Enablement Foundation for the Super Special Talents of Jiangsu UniversityProject(20071108)supported by the Technical Enablement Foundation of Ministry of Education for the Returned ScholarsProject(20060299006)supported by the PhD Programs Foundation of Ministry of Education of China
文摘The 6351 wrought aluminum alloy and K2TiF6-CaF2-LiCl components were selected as raw materials to fabricate in situ Al3Ti particulate reinforced aluminum alloy at 720℃via direct melt reaction method with electromagnetic stirring(EMS).CaF2 and LiCl acted as fluxes to lower the reaction temperature of the system.It is shown that the electromagnetic stirring and fluxes accelerate the emulsion process of K2TiF6.Optical microscopy,scanning electron microscopy,transmission electron microscopy and energy dispersive spectrum were utilized to analyze the microstructure and components of composites.Compared to composites fabricated without EMS and fluxes,the sizes of endogenetic Al3Ti are refined from 10-15μm to 2-4μm,which are often accompanied with silicon element.The morphology of Al3Ti or Al3TiSi0.22 exhibits triangle,quadrilateral and other clumpy patterns. Because of the Ca elements from CaF2,the sizes of Mg2Si decrease from 8-10μm to 1-2μm due to the formation of Ca2Si.
基金supported by the National Natural Science Foundation of China (grant numbers U1508216, 51501195, 51771194, 51771201)Liaoning Province (20180551101)+1 种基金the Innovation Fund of IMR (2017-PY10)S.J.Z acknowledges ‘Thousand Youth Talents Plan’ of China
文摘B4C particulate-reinforced 6061A1 composite was fabricated by powder metallurgy method. The as-rolled composite possesses high tensile strength which is comparable to that of the peak-aged 6061A1 alloy. More importantly, the microstructures and mechanical properties are thermally stable during long-term holding at elevated temperature (400℃). The microstructual contributions to the strength of the composite were discussed. Transmission electron microscopy (TEM) analysis indicates that the in-situ formed reinforcement Mg(Al)B2, as products of the interfacial reactions between B4C and the aluminum matrix, show not only good resistance to thermal coarsening but also strong pinning effect to the grain boundaries in the alloy matrix.
基金Item Sponsored by the Scientific Research Foundation for the Returned Overseas Chinese Scholars
文摘In cooling process of Fe-Cr-Al alloy oxidized at 1 300 ℃, the effect of cooling speed and exposure time on oxide spalled area fraction and successive variety of the spalled region were studied by investigating evolvement of the thermally grown oxide using in-situ CCD monitoring technique. The results showed that oxide spallation can be restrained by controlling cooling speed and the critical temperature drop of spallation initiation which is closely related to the oxide thickness or exposure time, and the spallation process of a little region may be described in more detail as two routes： from the oxide/substrate interface micro-decohesion, micro-buckles, buckle spreading, buckle crack to spallation and from the interface micro-decohesion, micro-buckles, buckle crack and spallation to the residual oxide decohesion and spallation.
