The microstructure of Al-Fe-V-Si-Nd alloy prepared by rapid solidification (RS) processing was studied by X-ray diffraction (XRD), transmission electron microscopy (TEM) and high resolution electron microscopy (HREM)....The microstructure of Al-Fe-V-Si-Nd alloy prepared by rapid solidification (RS) processing was studied by X-ray diffraction (XRD), transmission electron microscopy (TEM) and high resolution electron microscopy (HREM). The phase selection of the alloy during solidification and the nucleation behavior of Al8Fe4Nd phase were analyzed within the framework of time-dependent nucleation theory. The incubation time for Al8Fe4Nd phase was found shorter and the nucleation rate higher than those of α-Al. The results indicate the nucleation of Al8Fe4Nd phase is heterogeneous and the dispersoids of Al8Fe4Nd form as primary particles from the liquid, which is consistent with experimental observation.展开更多
Microstructure evolution of rare earth rich phase of rapidly-solidified (RS) TiAl based alloys was investigated. The two rapid-solidification techniques employed are melt-spinning technique (MS) and Hammer-and-Anvil t...Microstructure evolution of rare earth rich phase of rapidly-solidified (RS) TiAl based alloys was investigated. The two rapid-solidification techniques employed are melt-spinning technique (MS) and Hammer-and-Anvil technique (HB). MS ribbons and HA foils were obtained in the experiment. The results demonstrate that with the increasing of cooling rates of TiAl based alloys great changes are taken place in the microstructures of rare earth rich phase, from scattering mainly on grain boundaries of as-cast ingot to distributing homogeneously as very fine fibers or powders (nanometer grade) on the matrix. The fine paralleling second phase fibers in the HA foils are considered to be connected with gamma/alpha (2) lamellar colonies. Selected area electronic diffraction (SAED) patterns of the rare earth rich phase is in accordance with that of intermetallic AlCe.展开更多
Iron-based amorphous alloys have attracted technological and scientific interests due to their excellent soft magnetic properties. The typical nanocrystalline alloy with the composition of Fe73.5Cu1Nb3Si13.5B9 known a...Iron-based amorphous alloys have attracted technological and scientific interests due to their excellent soft magnetic properties. The typical nanocrystalline alloy with the composition of Fe73.5Cu1Nb3Si13.5B9 known as FINEMENT has been studied for structural properties analysis. Recently, it is found that after proper annealing the amorphous alloy like Fe73.5Cu1Nb3Si13.5B9 has a transition to the nanocrystalline state, thus exhibiting good magnetic properties. The alloy in the form of ribbon of 10 mm width and 25mm thickness with the composition of Fe73.5Cu1Nb3Si13.5B9 was prepared by rapid quenching method. The prepared ribbon sample has been annealed for 30 min in a controlled way in the temperature range 490℃ - 680℃. By analyzing X-ray diffraction (XRD) patterns, various structural parameters such as lattice parameters, grain size and silicon content of the nanocrystalline Fe(Si) grains, crystallization behavior and nanocrystalline phase formation have been investigated. In the nanocrystalline state, Cu helps the nucleation of α-Fe(Si) grains while Nb controls their growth, Si and B has been used as glass forming materials. Thus on the residual amorphous, the nanometric Fe(Si) grains develops. From broadening of fundamental peaks, the optimum grain size has been determined in the range of 7 - 23 nm.展开更多
Compositional dependences on microstructures and martensitic transformation behaviors in（Cu_（0.5）Zr_（0.5））_（100-x）Zn_x（x=1.5,2.5,4.5,7.0,10.0,and 14.0at.%）alloys were investigated.It was found that CuZr mart...Compositional dependences on microstructures and martensitic transformation behaviors in（Cu_（0.5）Zr_（0.5））_（100-x）Zn_x（x=1.5,2.5,4.5,7.0,10.0,and 14.0at.%）alloys were investigated.It was found that CuZr martensites were present in the present alloys.With increasing Zn content,the volume fractions of CuZr martensitic crystals and B2 CuZr phase gradually decrease and increase,respectively.With the addition of high Zn contents（i.e.,7.0,10.0,and 14.0at.%）,the matrix proves to be eutectic.Thermal analysis results show that the initial martensitic transformation temperature（M_s）decreases from（412±5）K to（329±5）K as the Zn content increases from 1.5at.% to14.0at.%.The values of Msof Cu-Zr-Zn shape memory alloys are inversely proportional to the number and concentrations of valence electrons（i.e.,e_v/a and c_v）,respectively,implying that the martensitic transformation in CuZrZn alloys could be of electronic nature.展开更多
基金The financial supports from the National Science Foundation of China (Grant No 59771020) Post-doctoral Foundation of China.
文摘The microstructure of Al-Fe-V-Si-Nd alloy prepared by rapid solidification (RS) processing was studied by X-ray diffraction (XRD), transmission electron microscopy (TEM) and high resolution electron microscopy (HREM). The phase selection of the alloy during solidification and the nucleation behavior of Al8Fe4Nd phase were analyzed within the framework of time-dependent nucleation theory. The incubation time for Al8Fe4Nd phase was found shorter and the nucleation rate higher than those of α-Al. The results indicate the nucleation of Al8Fe4Nd phase is heterogeneous and the dispersoids of Al8Fe4Nd form as primary particles from the liquid, which is consistent with experimental observation.
文摘Microstructure evolution of rare earth rich phase of rapidly-solidified (RS) TiAl based alloys was investigated. The two rapid-solidification techniques employed are melt-spinning technique (MS) and Hammer-and-Anvil technique (HB). MS ribbons and HA foils were obtained in the experiment. The results demonstrate that with the increasing of cooling rates of TiAl based alloys great changes are taken place in the microstructures of rare earth rich phase, from scattering mainly on grain boundaries of as-cast ingot to distributing homogeneously as very fine fibers or powders (nanometer grade) on the matrix. The fine paralleling second phase fibers in the HA foils are considered to be connected with gamma/alpha (2) lamellar colonies. Selected area electronic diffraction (SAED) patterns of the rare earth rich phase is in accordance with that of intermetallic AlCe.
文摘Iron-based amorphous alloys have attracted technological and scientific interests due to their excellent soft magnetic properties. The typical nanocrystalline alloy with the composition of Fe73.5Cu1Nb3Si13.5B9 known as FINEMENT has been studied for structural properties analysis. Recently, it is found that after proper annealing the amorphous alloy like Fe73.5Cu1Nb3Si13.5B9 has a transition to the nanocrystalline state, thus exhibiting good magnetic properties. The alloy in the form of ribbon of 10 mm width and 25mm thickness with the composition of Fe73.5Cu1Nb3Si13.5B9 was prepared by rapid quenching method. The prepared ribbon sample has been annealed for 30 min in a controlled way in the temperature range 490℃ - 680℃. By analyzing X-ray diffraction (XRD) patterns, various structural parameters such as lattice parameters, grain size and silicon content of the nanocrystalline Fe(Si) grains, crystallization behavior and nanocrystalline phase formation have been investigated. In the nanocrystalline state, Cu helps the nucleation of α-Fe(Si) grains while Nb controls their growth, Si and B has been used as glass forming materials. Thus on the residual amorphous, the nanometric Fe(Si) grains develops. From broadening of fundamental peaks, the optimum grain size has been determined in the range of 7 - 23 nm.
基金Item Sponsored by National Natural Science Foundation of China(51501103)Fundamental Research Funds for the Central Universities on Northwestern Polytechnical University of China(GEKY1008)
文摘Compositional dependences on microstructures and martensitic transformation behaviors in（Cu_（0.5）Zr_（0.5））_（100-x）Zn_x（x=1.5,2.5,4.5,7.0,10.0,and 14.0at.%）alloys were investigated.It was found that CuZr martensites were present in the present alloys.With increasing Zn content,the volume fractions of CuZr martensitic crystals and B2 CuZr phase gradually decrease and increase,respectively.With the addition of high Zn contents（i.e.,7.0,10.0,and 14.0at.%）,the matrix proves to be eutectic.Thermal analysis results show that the initial martensitic transformation temperature（M_s）decreases from（412±5）K to（329±5）K as the Zn content increases from 1.5at.% to14.0at.%.The values of Msof Cu-Zr-Zn shape memory alloys are inversely proportional to the number and concentrations of valence electrons（i.e.,e_v/a and c_v）,respectively,implying that the martensitic transformation in CuZrZn alloys could be of electronic nature.
基金Project (50271054) supported by the National Natural Science Foundation of ChinaProject (20070700003) supported by the Doctorate Programs Foundation of Ministry of Education of China+1 种基金Project (102102210031) supported by the Science and Technologies Foundation of Henan Province,ChinaProject (2010A430008) supported by the Natural Science Foundation of Henan Educational Committee of China
基金financially supported by the National Natural Science Foundation of China (No.51804010)the 2020 Yuyou Talent Training Plan Project of North China University of Technology,China (No.214051360020XN212/014)the R&D Program of Beijing Municipal Education Commission,China (No.KM201910009007)。
