The effectsof melt overheating degree on the undercooling degree and resultant solidification structures of Nd9Fe85-xTi4C2Bx（x=10, 12） glass-forming alloyswerestudied by differential thermal analysis combining with ...The effectsof melt overheating degree on the undercooling degree and resultant solidification structures of Nd9Fe85-xTi4C2Bx（x=10, 12） glass-forming alloyswerestudied by differential thermal analysis combining with solidification structure analysis. The results indicate that the undercooling degree of Nd9Fe85-xTi4C2Bx（x=10, 12） alloys significantly increaseswith the rise of melt overheating degree, and two overheating degree thresholds corresponding to the drastic increase of the mean undercooling degree are found for each of the alloys. The existence of two turning points of the mean undercooling degreescan be linked to the structure transitions inside the overheated melts, which result in the evident increase of volume fraction of amorphous phasein the solidified structures.展开更多
Various undercoolings 14-232 K of bulk K4169 superalloys were obtained by the method of molten glass fluxing combined with superheating cycling and the mechanical properties of undercooled K4169 with as-solidified sta...Various undercoolings 14-232 K of bulk K4169 superalloys were obtained by the method of molten glass fluxing combined with superheating cycling and the mechanical properties of undercooled K4169 with as-solidified state were tested. Microstructures and phases composition in undercooled bulk K4169 superalloy were identified by transmission electron microscope （TEM）, scanning electron microscope （SEM） and optical microscopy （OM）. The morphology of dendrites, grain size and intergranular phase all change with the increased undercooling. Meanwhile, the relationship between microstructure of undercooled K4169 superalloy and tensile properties was investigated. The experimental results show that the uniform distribution of Laves phase and the decrease of grain size and intergranular phase content are favorable for the improvement of mechanical properties. The maximum tensile strength and elongation obtained at undercooling of 232 K are 932.2 MPa and 6.5%, respectively.展开更多
This research investigated the combined effects of addition of Bi and Sb elements on the microstructure,thermal properties,ultimate tensile strength,ductility,and hardness of Sn−0.7Ag−0.5Cu(SAC0705)solder alloys.The r...This research investigated the combined effects of addition of Bi and Sb elements on the microstructure,thermal properties,ultimate tensile strength,ductility,and hardness of Sn−0.7Ag−0.5Cu(SAC0705)solder alloys.The results indicated that the addition of Bi and Sb significantly reduced the undercooling of solders,refined theβ-Sn phase and extended the eutectic areas of the solders.Moreover,the formation of SbSn and Bi phases in the solder matrix affected the mechanical properties of the solder.With the addition of 3 wt.%Bi and 3 wt.%Sb,the ultimate tensile strength and hardness of the SAC0705 base alloy increased from 31.26 MPa and 15.07 HV to 63.15 MPa and 23.68 HV,respectively.Ductility decreased due to grain boundary strengthening,solid solution strengthening,and precipitation strengthening effects,and the change in the fracture mechanism of the solder alloys.展开更多
The solid-state magnetic cooling(MC)method based on the magnetocaloric effect(MCE)is recognized as an environmentally friendly and high-energy-efficiency technology.The search or design of suitable magnetic materials ...The solid-state magnetic cooling(MC)method based on the magnetocaloric effect(MCE)is recognized as an environmentally friendly and high-energy-efficiency technology.The search or design of suitable magnetic materials with large MCEs is one of the main targets at present.In this work,we apply the chemical and hydrostatic pressures in the Ni_(35)Co_(15)Mn_(35-x)Fe_(x)Ti_(15) all-d-metal Heusler alloys and systematically investigate their crystal structures,phases,and magnetocaloric performances experimentally and theoretically.All the alloys are found to crystallize in an ordered B2-type structure at room temperature and the atoms of Fe are confirmed to all occupy at sites Mn(B).The total magnetic moments decrease gradually with increasing Fe content and decreasing of volume as well.The martensitic transformation temperature decreases with the increase of Fe content,whereas increases with increasing hydrostatic pressure.Moreover,obviously enhanced magnetocaloric performances can also be obtained by applied pressures.The maximum values of magnetic entropy change and refrigeration capacity are as high as 15.61(24.20)J(kg K)^(−1) and 109.91(347.26)J kg^(−1) withΔH=20(50)kOe,respectively.These magnetocaloric performances are superior to most of the recently reported famous materials,indicating the potential application for active MC.展开更多
基金Projects(51174121,51274125)supported by the National Natural Science Foundation of ChinaProject(2010R50016-30)supported by Zhejiang Province Science and Technology Innovation Team of Key Projects,ChinaProject supported by the K.C.Wong Magna Fund of Ningbo University,China
文摘The effectsof melt overheating degree on the undercooling degree and resultant solidification structures of Nd9Fe85-xTi4C2Bx（x=10, 12） glass-forming alloyswerestudied by differential thermal analysis combining with solidification structure analysis. The results indicate that the undercooling degree of Nd9Fe85-xTi4C2Bx（x=10, 12） alloys significantly increaseswith the rise of melt overheating degree, and two overheating degree thresholds corresponding to the drastic increase of the mean undercooling degree are found for each of the alloys. The existence of two turning points of the mean undercooling degreescan be linked to the structure transitions inside the overheated melts, which result in the evident increase of volume fraction of amorphous phasein the solidified structures.
基金Project(2011CB610406)supported by the National Basic Research Program of China
文摘Various undercoolings 14-232 K of bulk K4169 superalloys were obtained by the method of molten glass fluxing combined with superheating cycling and the mechanical properties of undercooled K4169 with as-solidified state were tested. Microstructures and phases composition in undercooled bulk K4169 superalloy were identified by transmission electron microscope （TEM）, scanning electron microscope （SEM） and optical microscopy （OM）. The morphology of dendrites, grain size and intergranular phase all change with the increased undercooling. Meanwhile, the relationship between microstructure of undercooled K4169 superalloy and tensile properties was investigated. The experimental results show that the uniform distribution of Laves phase and the decrease of grain size and intergranular phase content are favorable for the improvement of mechanical properties. The maximum tensile strength and elongation obtained at undercooling of 232 K are 932.2 MPa and 6.5%, respectively.
基金supported by the Division of Physical Science,Faculty of Science,Prince of Songkla University (PSU),Thailand
文摘This research investigated the combined effects of addition of Bi and Sb elements on the microstructure,thermal properties,ultimate tensile strength,ductility,and hardness of Sn−0.7Ag−0.5Cu(SAC0705)solder alloys.The results indicated that the addition of Bi and Sb significantly reduced the undercooling of solders,refined theβ-Sn phase and extended the eutectic areas of the solders.Moreover,the formation of SbSn and Bi phases in the solder matrix affected the mechanical properties of the solder.With the addition of 3 wt.%Bi and 3 wt.%Sb,the ultimate tensile strength and hardness of the SAC0705 base alloy increased from 31.26 MPa and 15.07 HV to 63.15 MPa and 23.68 HV,respectively.Ductility decreased due to grain boundary strengthening,solid solution strengthening,and precipitation strengthening effects,and the change in the fracture mechanism of the solder alloys.
基金supported by the National Natural Science Foundation of China(52001102 and 91963123)the Ten Thousand Talents Plan of Zhejiang Province of China(2018R52003)the Fundamental Research Funds for the Provincial University of Zhejiang(GK199900299012-022)。
文摘The solid-state magnetic cooling(MC)method based on the magnetocaloric effect(MCE)is recognized as an environmentally friendly and high-energy-efficiency technology.The search or design of suitable magnetic materials with large MCEs is one of the main targets at present.In this work,we apply the chemical and hydrostatic pressures in the Ni_(35)Co_(15)Mn_(35-x)Fe_(x)Ti_(15) all-d-metal Heusler alloys and systematically investigate their crystal structures,phases,and magnetocaloric performances experimentally and theoretically.All the alloys are found to crystallize in an ordered B2-type structure at room temperature and the atoms of Fe are confirmed to all occupy at sites Mn(B).The total magnetic moments decrease gradually with increasing Fe content and decreasing of volume as well.The martensitic transformation temperature decreases with the increase of Fe content,whereas increases with increasing hydrostatic pressure.Moreover,obviously enhanced magnetocaloric performances can also be obtained by applied pressures.The maximum values of magnetic entropy change and refrigeration capacity are as high as 15.61(24.20)J(kg K)^(−1) and 109.91(347.26)J kg^(−1) withΔH=20(50)kOe,respectively.These magnetocaloric performances are superior to most of the recently reported famous materials,indicating the potential application for active MC.
