The effect of addition temperature of MgO particles(MgOp)on their dispersion behavior and the efficiency of grain refinement in AZ31 Mg alloy was investigated.In addition,the grain refinement mechanism was systematica...The effect of addition temperature of MgO particles(MgOp)on their dispersion behavior and the efficiency of grain refinement in AZ31 Mg alloy was investigated.In addition,the grain refinement mechanism was systematically studied by microstructure characterization,thermodynamic calculation,and analysis of solidification curves.The results show that the grain size of AZ31 Mg alloy initially decreases and then increases as the MgOp addition temperature is increased from 720 to 810℃,exhibiting a minimum value of 136μm at 780℃.The improved grain refinement efficiency with increasing MgOp addition temperature can be attributed to the reduced Mg melt viscosity and enhanced wettability between MgOp and Mg melt.Furthermore,a corresponding physical model describing the solidification behavior and grain refinement mechanism was proposed.展开更多
Nucleation of dendritic primaryα（Al） phase with addition of element Ce and Sr in hypoeutectic Al-7%Si-Mg cast alloy was investigated by using differential scanning calorimetry （DSC） and scanning electron microsco...Nucleation of dendritic primaryα（Al） phase with addition of element Ce and Sr in hypoeutectic Al-7%Si-Mg cast alloy was investigated by using differential scanning calorimetry （DSC） and scanning electron microscopy. DSC results were used to calculate the activation energy and nucleation work of primaryα（Al） phase. The results show that the values of activation energy and nucleation work are decreased and the nucleation frequency is increased with the additions of Ce and Sr to the alloys. Moreover, the grain size of dendriticα（Al） phase is well refined, and the nucleation temperatures of primaryα（Al） dendrites are decreased with the additions of Ce and Sr. The effects of elements Ce and Sr additions on kinetic nucleation of primary α（Al） phases were also discussed in hypoeutectic Al-7%Si-Mg cast alloy.展开更多
In order to optimize the ductility of orthorhombic Ti2AlNb-based alloys sheet,Ti22Al27Nb sheet was treated by high density electropulsing（J max =6.80 7.09 kA/mm2,tp =110 μs） under ambient condition.Microstructures ...In order to optimize the ductility of orthorhombic Ti2AlNb-based alloys sheet,Ti22Al27Nb sheet was treated by high density electropulsing（J max =6.80 7.09 kA/mm2,tp =110 μs） under ambient condition.Microstructures were observed by SEM,and the tensile properties were also studied using uniaxial tension tests.The experimental results show that electropulsing can refine the microstructures of Ti22Al27Nb sheets.The specimen with the fine and homogeneous microstructures has good plasticity,and its elongation reaches 19.4%.The mechanism about the effect of electropulsing treatment on the microstructure of Ti22Al27Nb sheets was discussed.It was thought that the increase in nucleation rate during phase transformation and a very short treating time were regarded as the main reasons of producing smaller grains and increase in the plasticity by electropulsing.展开更多
Utilizing oxide inclusion to induce heterogeneous nucleation event is an available method to achieve grain refinement.In this study,Mg−Al binary alloys were refined by inoculation of in-situ oxidation process.Results ...Utilizing oxide inclusion to induce heterogeneous nucleation event is an available method to achieve grain refinement.In this study,Mg−Al binary alloys were refined by inoculation of in-situ oxidation process.Results show that MgO and MgAl_(2)O_(4) phases are primary oxide products for Mg−xAl alloys inoculated by in-situ oxidation.For pure Mg and Mg−1Al alloy,MgO is the only oxide product.MgAl_(2)O_(4) is another oxide product for Mg−xAl alloy as Al content increases to 3 wt.%.For Mg−3Al alloy,average grain size significantly decreases from 1135 to 237μm,with a high grain refining ratio of 79.1%.Both MgO and MgAl_(2)O_(4) possess nucleating potency forα-Mg grain.MgAl_(2)O_(4) exhibits a higher nucleating potency due to the lower misfit withα-Mg.The grain refinement of Mg−xAl alloys inoculated by in-situ oxidation process is attributed to heterogeneous nucleation events ofα-Mg grains on MgO or MgAl_(2)O_(4) particles.展开更多
A general expression for the relationship between induction periodand supersaturation was developed based on polynuclear approach.Different mechanism of primary nucleation in solution can beillustrated by the expressi...A general expression for the relationship between induction periodand supersaturation was developed based on polynuclear approach.Different mechanism of primary nucleation in solution can beillustrated by the expression. The results of induction perioddetermined by laser scattering method shows that the crystallizationof ciprofloxacin hydrochloride monohydrate in water/ethanol oraqueous solution is by the mechanism of primary nucleation followedby one-dimensional diffusion growth, and then on-dimensionalcontinuous or 'birth and spread' growth on crystal face. The growthmechanism on the crystal face is affected by temperature and solvent.展开更多
The effect of boron content on grain refinement of commercially pure aluminum by Al-5Ti-1B was quantitatively assessed.When the boron content is less than 0.03 wt.%,the refining performance of Al-5Ti-1B gradually is w...The effect of boron content on grain refinement of commercially pure aluminum by Al-5Ti-1B was quantitatively assessed.When the boron content is less than 0.03 wt.%,the refining performance of Al-5Ti-1B gradually is weakened as the boron content increases,which is attributed to the reaction of boron with the Al_(3)Ti interlayer on TiB_(2)and the consumption of solute Ti.On the contrary,when the boron content exceeds 0.03 wt.%,the refining performance of Al-5Ti-1B gradually recovers with increasing boron content,which is related to the formation of primary AlB_(2)particles that provide additional nucleant substrates.展开更多
基金the National Natural Science Foundation of China(No.51871155).
文摘The effect of addition temperature of MgO particles(MgOp)on their dispersion behavior and the efficiency of grain refinement in AZ31 Mg alloy was investigated.In addition,the grain refinement mechanism was systematically studied by microstructure characterization,thermodynamic calculation,and analysis of solidification curves.The results show that the grain size of AZ31 Mg alloy initially decreases and then increases as the MgOp addition temperature is increased from 720 to 810℃,exhibiting a minimum value of 136μm at 780℃.The improved grain refinement efficiency with increasing MgOp addition temperature can be attributed to the reduced Mg melt viscosity and enhanced wettability between MgOp and Mg melt.Furthermore,a corresponding physical model describing the solidification behavior and grain refinement mechanism was proposed.
基金Project (42-QP-009) support by Research Fund of the State Key Laboratory of Solidification Processing,ChinaProject (B08040) supported by the Program of Introducing Talents of Discipline to Universities ("111"Project),China
文摘Nucleation of dendritic primaryα（Al） phase with addition of element Ce and Sr in hypoeutectic Al-7%Si-Mg cast alloy was investigated by using differential scanning calorimetry （DSC） and scanning electron microscopy. DSC results were used to calculate the activation energy and nucleation work of primaryα（Al） phase. The results show that the values of activation energy and nucleation work are decreased and the nucleation frequency is increased with the additions of Ce and Sr to the alloys. Moreover, the grain size of dendriticα（Al） phase is well refined, and the nucleation temperatures of primaryα（Al） dendrites are decreased with the additions of Ce and Sr. The effects of elements Ce and Sr additions on kinetic nucleation of primary α（Al） phases were also discussed in hypoeutectic Al-7%Si-Mg cast alloy.
基金Project(50875061) supported by the National Natural Science Foundation of ChinaProject(20092302110016) supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘In order to optimize the ductility of orthorhombic Ti2AlNb-based alloys sheet,Ti22Al27Nb sheet was treated by high density electropulsing（J max =6.80 7.09 kA/mm2,tp =110 μs） under ambient condition.Microstructures were observed by SEM,and the tensile properties were also studied using uniaxial tension tests.The experimental results show that electropulsing can refine the microstructures of Ti22Al27Nb sheets.The specimen with the fine and homogeneous microstructures has good plasticity,and its elongation reaches 19.4%.The mechanism about the effect of electropulsing treatment on the microstructure of Ti22Al27Nb sheets was discussed.It was thought that the increase in nucleation rate during phase transformation and a very short treating time were regarded as the main reasons of producing smaller grains and increase in the plasticity by electropulsing.
基金supported by the National Natural Science Foundation of China(No.51871100).
文摘Utilizing oxide inclusion to induce heterogeneous nucleation event is an available method to achieve grain refinement.In this study,Mg−Al binary alloys were refined by inoculation of in-situ oxidation process.Results show that MgO and MgAl_(2)O_(4) phases are primary oxide products for Mg−xAl alloys inoculated by in-situ oxidation.For pure Mg and Mg−1Al alloy,MgO is the only oxide product.MgAl_(2)O_(4) is another oxide product for Mg−xAl alloy as Al content increases to 3 wt.%.For Mg−3Al alloy,average grain size significantly decreases from 1135 to 237μm,with a high grain refining ratio of 79.1%.Both MgO and MgAl_(2)O_(4) possess nucleating potency forα-Mg grain.MgAl_(2)O_(4) exhibits a higher nucleating potency due to the lower misfit withα-Mg.The grain refinement of Mg−xAl alloys inoculated by in-situ oxidation process is attributed to heterogeneous nucleation events ofα-Mg grains on MgO or MgAl_(2)O_(4) particles.
文摘A general expression for the relationship between induction periodand supersaturation was developed based on polynuclear approach.Different mechanism of primary nucleation in solution can beillustrated by the expression. The results of induction perioddetermined by laser scattering method shows that the crystallizationof ciprofloxacin hydrochloride monohydrate in water/ethanol oraqueous solution is by the mechanism of primary nucleation followedby one-dimensional diffusion growth, and then on-dimensionalcontinuous or 'birth and spread' growth on crystal face. The growthmechanism on the crystal face is affected by temperature and solvent.
基金the financial supports from the National Natural Science Foundation of China(Nos.U1832183,52090042,51821001)。
文摘The effect of boron content on grain refinement of commercially pure aluminum by Al-5Ti-1B was quantitatively assessed.When the boron content is less than 0.03 wt.%,the refining performance of Al-5Ti-1B gradually is weakened as the boron content increases,which is attributed to the reaction of boron with the Al_(3)Ti interlayer on TiB_(2)and the consumption of solute Ti.On the contrary,when the boron content exceeds 0.03 wt.%,the refining performance of Al-5Ti-1B gradually recovers with increasing boron content,which is related to the formation of primary AlB_(2)particles that provide additional nucleant substrates.
