The evolution of the microstructure and morphology of Cu55Ni45 and Cu60Ni40 alloys under varying degrees of undercooling was investigated through molten glass purification and cyclic superheating technology.By increas...The evolution of the microstructure and morphology of Cu55Ni45 and Cu60Ni40 alloys under varying degrees of undercooling was investigated through molten glass purification and cyclic superheating technology.By increasing the Cu content,the effect of Cu on the evolution of the microstructure and morphology of the Cu-Ni alloy during undercooling was studied.The mechanism of grain refinement at different degrees of undercooling and the effect of Cu content on its solidification behaviour were investigated.The solidification behaviour of Cu55Ni45 and Cu60Ni40 alloys was investigated using infrared thermometry and high-speed photography.The results indicate that both Cu55Ni45 and Cu60Ni40 alloy melts undergo only one recalescence during rapid solidification.The degree of recalescence increases approximately linearly with increasing undercooling.The solidification front of the alloy melts undergoes a transition process from a small-angle plane to a sharp front and then to a smooth arc.However,the growth of the subcooled melt is constrained to a narrow range,facilitating the formation of a coarse dendritic crystal morphology in the Cu-Ni alloy.At large undercooling,the stress breakdown of the directionally growing dendrites is primarily caused by thermal diffusion.The strain remaining in the dendritic fragments provides the driving force for recrystallisation of the tissue to occur,which in turn refines the tissue.展开更多
By applying the rapid solidification technique of deep undercooling,Cu65Ni35 and Cu60Ni40 alloys achieved maximum undercoolings of 284 and 222 K,respectively.Microstructural images captured reveal grain refinement in ...By applying the rapid solidification technique of deep undercooling,Cu65Ni35 and Cu60Ni40 alloys achieved maximum undercoolings of 284 and 222 K,respectively.Microstructural images captured reveal grain refinement in both alloys across both large and small undercooling ranges.High-speed photography was used to analyze the relationship between solidification front morphology and undercooling,showing that dendrite remelting and fragmentation caused grain refinement under small undercooling,while stress-induced recrystallization is responsible under large undercooling.Microhardness testing further demonstrates a sudden drop in microhardness near the critical undercooling point,providing evidence for grain refinement due to recrystallization in large undercooling tissues.展开更多
The undercooling and solidification of 150 μm and 185 μm droplets of Sn 5%Pb alloy prepared by the uniform droplet spray (UDS) process have been investigated. The enthalpy of the droplet has been measured by non adi...The undercooling and solidification of 150 μm and 185 μm droplets of Sn 5%Pb alloy prepared by the uniform droplet spray (UDS) process have been investigated. The enthalpy of the droplet has been measured by non adiabatic calorimetric method as a function of the flight distance. A droplet solidification simulation model has been used to compare with the experimental data. The results show that the enthalpy released by the droplets in the calorimeter is 11.88 J/g and 22.29 J/g less than the simulated values up to a certain flight distance at 0.485 m and 0.460 m for 150 μm and 185 μm droplets respectively, but agrees with the expected values at larger distance. The nucleation of the droplets takes place at the distance where the experimental and simulated enthalpy values agree. The droplets quenched before nucleation solidify into metastable supersaturated solid solution and have large undercooling. The formation of the metastable structure in the droplets has been verified metallographically and by calculations based on a thermodynamic model.展开更多
Undercoolings up to 397 K(0.283 T_E)have been obtained for Ni-32.5% Sn eutectic alloy melted by superheating-cooling cycles and denucleating with inorganic glasses.The predomi- nant dissipation of heat for highly unde...Undercoolings up to 397 K(0.283 T_E)have been obtained for Ni-32.5% Sn eutectic alloy melted by superheating-cooling cycles and denucleating with inorganic glasses.The predomi- nant dissipation of heat for highly undercooled alloy melt is through radiation.An approxi- mate method is consequently derived to calculate its mean specific heat from measured cooling curves.With the aid of high speed cinematography,it is revealed that the surface or interface heterogeneous nucleation takes place in preference to homogeneous nucleation even though the undercooling has exceeded 0.2 T_E.展开更多
For the first time, the undercooling of a magnetostrictive material a near peritectic Tb 0.27 Dy 0.73 Fe 1.90 alloy was realized by vacuum electromagnetic levitation melting and 60 K undercooling was obt...For the first time, the undercooling of a magnetostrictive material a near peritectic Tb 0.27 Dy 0.73 Fe 1.90 alloy was realized by vacuum electromagnetic levitation melting and 60 K undercooling was obtained. There is one recalescence behavior during solidification of the undercooled melt,which can attribute to the priority precipitation of REFe 2 phase instead of REFe 3 phase, due to preferential nucleation and higher crystal growth rate of REFe 2 phase and the suppression of peritectic reaction. According to the crystal structural characteristics of REFe 2 and REFe 3, REFe 2 is a Laves phase intermetallics with MgCu 2 type structure, which has similar polytetrahedral structure with short range ordered structure in undercooled melt and has lower potential barrier for nucleation than that of REFe 3,which lead to the preferential nucleation of REFe 2 phase directly from the undercooled melt. Also, the similarity of structures between REFe 2 phase and undercooled melt leads to higher crystal growth rate of REFe 2 phase than that of REFe 3.展开更多
The paper presents some results of the investigation on effects of the fourth component(Ti,C,Sb or Cu)and undercooling on the morphology,size and forming process of primary Mg-Zn-Y icosahedral quasicrystal phase(I-pha...The paper presents some results of the investigation on effects of the fourth component(Ti,C,Sb or Cu)and undercooling on the morphology,size and forming process of primary Mg-Zn-Y icosahedral quasicrystal phase(I-phase)under normal casting conditions.The result shows that the addition of certain amount of fourth component can transform I-phase morphology from petal-like to spherical.However,I-phase will grow up to petal-like if superfluous addition of the fourth component applied.It is also found that the solidified morphology of I-phase depends on the stability of spherical I-phase during the subsequent growth,and critical radius of maintaining the spherical I-phase interface relatively stable.Further,mini-sized spherical I-phase can be produced with high content of the fourth component by undercooling.Such findings are beneficial for industrializing Mgbased quasicrystals.展开更多
Undercooling solidification under a magnetic field(UMF)is an effective way to tailor the microstructure and properties of Co-based alloys.In this study,by attributing to the UMF treatment,the strength−ductility trade-...Undercooling solidification under a magnetic field(UMF)is an effective way to tailor the microstructure and properties of Co-based alloys.In this study,by attributing to the UMF treatment,the strength−ductility trade-off dilemma in GH605 superalloy is successfully overcome.The UMF treatment can effectively refine the grains and increase the solid solubility,leading to the high yield strength.The main deformation mechanism in the as-forged alloy is dislocation slipping.By contrast,multiple deformation mechanisms,including stacking faults,twining,dislocation slipping,and their strong interactions are activated in the UMF-treated sample during compression deformation,which enhances the strength and ductility simultaneously.In addition,the precipitation of hard Laves phases along the grain boundaries can be obtained after UMF treatment,hindering crack propagation during compression deformation.展开更多
The effect of the gradient content of Co element on the solidification process of Cu-based alloy under deep under cooling conditions was explored.The non-equilibrium solidification structure of the under cooled alloy ...The effect of the gradient content of Co element on the solidification process of Cu-based alloy under deep under cooling conditions was explored.The non-equilibrium solidification structure of the under cooled alloy samples were analyzed.It is found that the rapidly solidified alloy has undergone twice grain refinement during the undercooling process.Characterization and significance of the maximum undercooling refinement structure of Cu60Ni35Co5 at T=253 K were analyzed.High-density defects were observed,such as dislocations,stacking faults networks,and twinning structures.The standard FCC diffraction pattern represents that it is still a single-phase structure.Based on the metallographic diagram,EBSD and TEM data analysis,it is illustrated that the occurrence of grain refinement under high undercooling is due to stress induced recrystallization.In addition,the laser cladding technology is used to coat Co-based alloy(Stellite12) coating on 304 stainless steel substrate;the microstructure of the coating cross-section was analyzed.It was found that the microstructure of the cross-section is presented as columnar crystals,planar crystals,and disordered growth direction,so that the coating has better hardness and wear resistance.By electrochemical corrosion of the substrate and coating,it can be seen that the Co and Cr elements present in the coating are more likely to form a dense passivation film,which improved the corrosion resistance of the coating.展开更多
Nd_9Fe_（85–x）Ti_4C_2B_x（x=10–15） magnetic alloys were investigated by differential thermal analysis and X-ray diffraction analysis. The results showed that with the B content increasing from 10 at.% to 15 at.%, ...Nd_9Fe_（85–x）Ti_4C_2B_x（x=10–15） magnetic alloys were investigated by differential thermal analysis and X-ray diffraction analysis. The results showed that with the B content increasing from 10 at.% to 15 at.%, the liquidus temperatures TL of the alloys decreased from 1498.5 to 1472.5 K; the solidus temperatures TS of them increased from 1353.2 to 1358.3 K; and the nucleation undercooling of the alloy melts cooled at the rate of 40 K/min decreased from 122.8 to 95.9 K, resulting in the solidification structures consisting of Nd_2Fe_（14）B, Fe_3B, α-Fe, Nd1.1Fe4B4 and TiC nanocrystallines. Furthermore, the Nd_9Fe_（85–x）Ti_4C_2B_x（x=11, 13, 15） bulk alloys in sheet form with the thickness of 0.7 mm were prepared by copper mold suction casting and their solidification characteristics and solidification structures under sub-rapidly cooling rate were investigated. The results showed that partially amorphous structures were obtained in the as-cast bulk alloys and the amount of amorphous decreased with the increase of the B content. By annealing the as-cast bulk alloys at 923 K for 10 min, the nanocomposite microstructures composed with Nd_2Fe_（14）B, Fe_3B and α-Fe nanocrystallines, which showed a single-phase hard magnetic behavior and enhanced magnetic properties, were achieved.展开更多
A new concept of undercooling heredity is developed to evaluate the undercooling ability in a non catalytic nucleation coated mould, where alloy melts were highly undercooled previously. Before the heredity experiment...A new concept of undercooling heredity is developed to evaluate the undercooling ability in a non catalytic nucleation coated mould, where alloy melts were highly undercooled previously. Before the heredity experiment a non catalytic nucleation composite glass lined coating (B F) was prepared on the inner surface of mould and the Cu 70 Ni 30 alloy was selected to perform undercooling experiment in the B F non catalytic coating mould. Its ratio of undercooling heredity was 0.76. The results prove that the B F coating is an ideal non catalytic media for purified Cu 70 Ni 30 alloy melts due to its small contact angle between the melt and coating layer. Considering that various microstructures form under different undercoolings, two critical undercoolings, Δ T 1 and Δ T 2, and their corresponding microstructures of Cu 70 Ni 30 alloy are well defined. Moreover, it is found that the manned trigging solidification in the non catalytic coating mould could be used to get directional undercooling dendrite structure while the melt undercooling is larger than the critical undercooling Δ T 2.展开更多
The rapid quenching and large undercooling phenomena and device working principle in the rapid solidification process are analyzed, and the working characteristics are presented in detail. The results show that these ...The rapid quenching and large undercooling phenomena and device working principle in the rapid solidification process are analyzed, and the working characteristics are presented in detail. The results show that these multistage device are ideal for making amorphous, quasicrystalline, microcrystalline and fine metallic powders.展开更多
A comprehensive petrographic observation contributes to classification of various textures in welded tuffs into two types, the textures in plastic fragments and the ones in rigid fragments. A detailed petrographic stu...A comprehensive petrographic observation contributes to classification of various textures in welded tuffs into two types, the textures in plastic fragments and the ones in rigid fragments. A detailed petrographic study of the textures in plastic fragments leads to suggestion that thesetextures are not a type of devitrification textures. and also that they were formed not by devitrification but by undercooling crystallization. This viewpoint is supported by results of undercooling crystallization experiments. The petrographic characteristics of these textures are satisfactorily demonstrated by the undercooling crystallization theory.展开更多
The effects of a high magnetic field on the evolution of the single-phase interface and the liquid-solid interface energy in Al-Cu alloy were investigated experimentally.It is found that the application of the magneti...The effects of a high magnetic field on the evolution of the single-phase interface and the liquid-solid interface energy in Al-Cu alloy were investigated experimentally.It is found that the application of the magnetic field has a significant promotion effect on the migration of liquid droplets,accelerating the formation of the single-phase interface.This should be attributed to the thermoelectric(TE)magnetic convection in the droplets which has enhanced the diffusion and increased the migration speed of liquid droplets.Further,the effect of the high magnetic field on the solid-liquid interface energy is analyzed by an improved grain boundary groove(GBG)method.The average solid-liquid interface energy of theα-Al/Al-Cu and Al2Cu/Al-Cu systems increases and decreases with the increase of the magnetic field,respectively.The above experiment results are well explained based on the formation and interaction of the magnetic dipole at the solid-liquid interface.Moreover,experimental results reveal that the magnetic-field-induced interface energy increases and decreases the nucleation undercooling of the Al-30wt.%Cu alloy and Al-35wt.%Cu alloy,respectively.By studying the effect of the magnetic-field-induced interface energy on the nucleation undercooling,the understanding of the interface energy-induced nucleation undercooling deepens.展开更多
Poly （butylene succinatc-co-terephthalate） （PBST） copolycsters were prepared by polycondensation. The crystallization behavior of the as-prepared copolyesters was investigated by depolarized light intensity （DLI...Poly （butylene succinatc-co-terephthalate） （PBST） copolycsters were prepared by polycondensation. The crystallization behavior of the as-prepared copolyesters was investigated by depolarized light intensity （DLI） at high undercoolings. According to Avrami equation, the exponent n, independent of the crystallization temperature, is at a range of 2. 5 to 3. 4, which probably corresponds to the heterogeneous mucleation and a 3-dimensional spherulitic growth. The maximum crystallization rate, very useful to polymer processing, was found at about 90℃ based on the half-crystallization time t1/2 analysis.展开更多
基金Funded by the Basic Research Project in Shanxi Province(No.202103021224183)the 2024 Science and Technology PlanProject of Jiaozuo City,Henan Province(No.2024410001)。
文摘The evolution of the microstructure and morphology of Cu55Ni45 and Cu60Ni40 alloys under varying degrees of undercooling was investigated through molten glass purification and cyclic superheating technology.By increasing the Cu content,the effect of Cu on the evolution of the microstructure and morphology of the Cu-Ni alloy during undercooling was studied.The mechanism of grain refinement at different degrees of undercooling and the effect of Cu content on its solidification behaviour were investigated.The solidification behaviour of Cu55Ni45 and Cu60Ni40 alloys was investigated using infrared thermometry and high-speed photography.The results indicate that both Cu55Ni45 and Cu60Ni40 alloy melts undergo only one recalescence during rapid solidification.The degree of recalescence increases approximately linearly with increasing undercooling.The solidification front of the alloy melts undergoes a transition process from a small-angle plane to a sharp front and then to a smooth arc.However,the growth of the subcooled melt is constrained to a narrow range,facilitating the formation of a coarse dendritic crystal morphology in the Cu-Ni alloy.At large undercooling,the stress breakdown of the directionally growing dendrites is primarily caused by thermal diffusion.The strain remaining in the dendritic fragments provides the driving force for recrystallisation of the tissue to occur,which in turn refines the tissue.
基金Funded by the Basic Research Project in Shanxi Province(No.202103021224183)the 2024 Science and Technology Plan Project of Jiaozuo City,Henan Province(No.2024410001)。
文摘By applying the rapid solidification technique of deep undercooling,Cu65Ni35 and Cu60Ni40 alloys achieved maximum undercoolings of 284 and 222 K,respectively.Microstructural images captured reveal grain refinement in both alloys across both large and small undercooling ranges.High-speed photography was used to analyze the relationship between solidification front morphology and undercooling,showing that dendrite remelting and fragmentation caused grain refinement under small undercooling,while stress-induced recrystallization is responsible under large undercooling.Microhardness testing further demonstrates a sudden drop in microhardness near the critical undercooling point,providing evidence for grain refinement due to recrystallization in large undercooling tissues.
文摘The undercooling and solidification of 150 μm and 185 μm droplets of Sn 5%Pb alloy prepared by the uniform droplet spray (UDS) process have been investigated. The enthalpy of the droplet has been measured by non adiabatic calorimetric method as a function of the flight distance. A droplet solidification simulation model has been used to compare with the experimental data. The results show that the enthalpy released by the droplets in the calorimeter is 11.88 J/g and 22.29 J/g less than the simulated values up to a certain flight distance at 0.485 m and 0.460 m for 150 μm and 185 μm droplets respectively, but agrees with the expected values at larger distance. The nucleation of the droplets takes place at the distance where the experimental and simulated enthalpy values agree. The droplets quenched before nucleation solidify into metastable supersaturated solid solution and have large undercooling. The formation of the metastable structure in the droplets has been verified metallographically and by calculations based on a thermodynamic model.
文摘Undercoolings up to 397 K(0.283 T_E)have been obtained for Ni-32.5% Sn eutectic alloy melted by superheating-cooling cycles and denucleating with inorganic glasses.The predomi- nant dissipation of heat for highly undercooled alloy melt is through radiation.An approxi- mate method is consequently derived to calculate its mean specific heat from measured cooling curves.With the aid of high speed cinematography,it is revealed that the surface or interface heterogeneous nucleation takes place in preference to homogeneous nucleation even though the undercooling has exceeded 0.2 T_E.
文摘For the first time, the undercooling of a magnetostrictive material a near peritectic Tb 0.27 Dy 0.73 Fe 1.90 alloy was realized by vacuum electromagnetic levitation melting and 60 K undercooling was obtained. There is one recalescence behavior during solidification of the undercooled melt,which can attribute to the priority precipitation of REFe 2 phase instead of REFe 3 phase, due to preferential nucleation and higher crystal growth rate of REFe 2 phase and the suppression of peritectic reaction. According to the crystal structural characteristics of REFe 2 and REFe 3, REFe 2 is a Laves phase intermetallics with MgCu 2 type structure, which has similar polytetrahedral structure with short range ordered structure in undercooled melt and has lower potential barrier for nucleation than that of REFe 3,which lead to the preferential nucleation of REFe 2 phase directly from the undercooled melt. Also, the similarity of structures between REFe 2 phase and undercooled melt leads to higher crystal growth rate of REFe 2 phase than that of REFe 3.
基金supported by the Natural Science Fund of Hebei Province(E2008000045)Doctoral Science Foundation of Hebei University of Technology
文摘The paper presents some results of the investigation on effects of the fourth component(Ti,C,Sb or Cu)and undercooling on the morphology,size and forming process of primary Mg-Zn-Y icosahedral quasicrystal phase(I-phase)under normal casting conditions.The result shows that the addition of certain amount of fourth component can transform I-phase morphology from petal-like to spherical.However,I-phase will grow up to petal-like if superfluous addition of the fourth component applied.It is also found that the solidified morphology of I-phase depends on the stability of spherical I-phase during the subsequent growth,and critical radius of maintaining the spherical I-phase interface relatively stable.Further,mini-sized spherical I-phase can be produced with high content of the fourth component by undercooling.Such findings are beneficial for industrializing Mgbased quasicrystals.
基金the fund of National Key Laboratory for Precision Hot Processing of Metals,China(No.6142909200104)State Key Laboratory of Solidification Processing(NPU),China(No.2022-TS-08)National Training Program of Innovation and Entrepreneurship for Undergraduates.We thank Dr.ZHENG from ZKKF(Beijing)Science&Technology Company for supporting the characterization of the materials.
文摘Undercooling solidification under a magnetic field(UMF)is an effective way to tailor the microstructure and properties of Co-based alloys.In this study,by attributing to the UMF treatment,the strength−ductility trade-off dilemma in GH605 superalloy is successfully overcome.The UMF treatment can effectively refine the grains and increase the solid solubility,leading to the high yield strength.The main deformation mechanism in the as-forged alloy is dislocation slipping.By contrast,multiple deformation mechanisms,including stacking faults,twining,dislocation slipping,and their strong interactions are activated in the UMF-treated sample during compression deformation,which enhances the strength and ductility simultaneously.In addition,the precipitation of hard Laves phases along the grain boundaries can be obtained after UMF treatment,hindering crack propagation during compression deformation.
基金Funded by the Basic Research Projects in Shanxi Province(No.202103021224183)。
文摘The effect of the gradient content of Co element on the solidification process of Cu-based alloy under deep under cooling conditions was explored.The non-equilibrium solidification structure of the under cooled alloy samples were analyzed.It is found that the rapidly solidified alloy has undergone twice grain refinement during the undercooling process.Characterization and significance of the maximum undercooling refinement structure of Cu60Ni35Co5 at T=253 K were analyzed.High-density defects were observed,such as dislocations,stacking faults networks,and twinning structures.The standard FCC diffraction pattern represents that it is still a single-phase structure.Based on the metallographic diagram,EBSD and TEM data analysis,it is illustrated that the occurrence of grain refinement under high undercooling is due to stress induced recrystallization.In addition,the laser cladding technology is used to coat Co-based alloy(Stellite12) coating on 304 stainless steel substrate;the microstructure of the coating cross-section was analyzed.It was found that the microstructure of the cross-section is presented as columnar crystals,planar crystals,and disordered growth direction,so that the coating has better hardness and wear resistance.By electrochemical corrosion of the substrate and coating,it can be seen that the Co and Cr elements present in the coating are more likely to form a dense passivation film,which improved the corrosion resistance of the coating.
基金Project supported by National Natural Science Foundation of China(51174121,51274125)Zhejiang Province Science and Technology Innovation Team of Key Projects(2010R50016-30)
文摘Nd_9Fe_（85–x）Ti_4C_2B_x（x=10–15） magnetic alloys were investigated by differential thermal analysis and X-ray diffraction analysis. The results showed that with the B content increasing from 10 at.% to 15 at.%, the liquidus temperatures TL of the alloys decreased from 1498.5 to 1472.5 K; the solidus temperatures TS of them increased from 1353.2 to 1358.3 K; and the nucleation undercooling of the alloy melts cooled at the rate of 40 K/min decreased from 122.8 to 95.9 K, resulting in the solidification structures consisting of Nd_2Fe_（14）B, Fe_3B, α-Fe, Nd1.1Fe4B4 and TiC nanocrystallines. Furthermore, the Nd_9Fe_（85–x）Ti_4C_2B_x（x=11, 13, 15） bulk alloys in sheet form with the thickness of 0.7 mm were prepared by copper mold suction casting and their solidification characteristics and solidification structures under sub-rapidly cooling rate were investigated. The results showed that partially amorphous structures were obtained in the as-cast bulk alloys and the amount of amorphous decreased with the increase of the B content. By annealing the as-cast bulk alloys at 923 K for 10 min, the nanocomposite microstructures composed with Nd_2Fe_（14）B, Fe_3B and α-Fe nanocrystallines, which showed a single-phase hard magnetic behavior and enhanced magnetic properties, were achieved.
文摘A new concept of undercooling heredity is developed to evaluate the undercooling ability in a non catalytic nucleation coated mould, where alloy melts were highly undercooled previously. Before the heredity experiment a non catalytic nucleation composite glass lined coating (B F) was prepared on the inner surface of mould and the Cu 70 Ni 30 alloy was selected to perform undercooling experiment in the B F non catalytic coating mould. Its ratio of undercooling heredity was 0.76. The results prove that the B F coating is an ideal non catalytic media for purified Cu 70 Ni 30 alloy melts due to its small contact angle between the melt and coating layer. Considering that various microstructures form under different undercoolings, two critical undercoolings, Δ T 1 and Δ T 2, and their corresponding microstructures of Cu 70 Ni 30 alloy are well defined. Moreover, it is found that the manned trigging solidification in the non catalytic coating mould could be used to get directional undercooling dendrite structure while the melt undercooling is larger than the critical undercooling Δ T 2.
文摘The rapid quenching and large undercooling phenomena and device working principle in the rapid solidification process are analyzed, and the working characteristics are presented in detail. The results show that these multistage device are ideal for making amorphous, quasicrystalline, microcrystalline and fine metallic powders.
文摘A comprehensive petrographic observation contributes to classification of various textures in welded tuffs into two types, the textures in plastic fragments and the ones in rigid fragments. A detailed petrographic study of the textures in plastic fragments leads to suggestion that thesetextures are not a type of devitrification textures. and also that they were formed not by devitrification but by undercooling crystallization. This viewpoint is supported by results of undercooling crystallization experiments. The petrographic characteristics of these textures are satisfactorily demonstrated by the undercooling crystallization theory.
基金financed by the National Natural Science Foun-dation of China(Nos.51904183 and 52130204)the Inde-pendent Research and Development Project of State Key Labora-tory of Advanced Special Steel,Shanghai Key Laboratory of Ad-vanced Ferrometallurgy,Shanghai University(SKLASS 2021-Z07)the Science and Technology Commission of Shanghai Munic-ipality(Nos.19DZ2270200,20511107700).
文摘The effects of a high magnetic field on the evolution of the single-phase interface and the liquid-solid interface energy in Al-Cu alloy were investigated experimentally.It is found that the application of the magnetic field has a significant promotion effect on the migration of liquid droplets,accelerating the formation of the single-phase interface.This should be attributed to the thermoelectric(TE)magnetic convection in the droplets which has enhanced the diffusion and increased the migration speed of liquid droplets.Further,the effect of the high magnetic field on the solid-liquid interface energy is analyzed by an improved grain boundary groove(GBG)method.The average solid-liquid interface energy of theα-Al/Al-Cu and Al2Cu/Al-Cu systems increases and decreases with the increase of the magnetic field,respectively.The above experiment results are well explained based on the formation and interaction of the magnetic dipole at the solid-liquid interface.Moreover,experimental results reveal that the magnetic-field-induced interface energy increases and decreases the nucleation undercooling of the Al-30wt.%Cu alloy and Al-35wt.%Cu alloy,respectively.By studying the effect of the magnetic-field-induced interface energy on the nucleation undercooling,the understanding of the interface energy-induced nucleation undercooling deepens.
文摘Poly （butylene succinatc-co-terephthalate） （PBST） copolycsters were prepared by polycondensation. The crystallization behavior of the as-prepared copolyesters was investigated by depolarized light intensity （DLI） at high undercoolings. According to Avrami equation, the exponent n, independent of the crystallization temperature, is at a range of 2. 5 to 3. 4, which probably corresponds to the heterogeneous mucleation and a 3-dimensional spherulitic growth. The maximum crystallization rate, very useful to polymer processing, was found at about 90℃ based on the half-crystallization time t1/2 analysis.
