The influence of pure La, pure Ce, (La+Ce) mischmetal on the dendritical arm space(LDAS) of ZL105 alloy in cylinderical casting was studied. The effects of adding amount of (La+ Ce) mischmetal on LDAs and ultimate te...The influence of pure La, pure Ce, (La+Ce) mischmetal on the dendritical arm space(LDAS) of ZL105 alloy in cylinderical casting was studied. The effects of adding amount of (La+ Ce) mischmetal on LDAs and ultimate tensile strength(b) were investigated, and the relationship between b and LDAS was founded. (La+Ce) mischmetal has stronger ability to refine LDAs than pure La or pure Ce. The proper adding amounts of it is 0.15% (mass fraction). LDAs has a remarkable effect on ah of casting, which can be predicted by the regression equation obtained in this work.展开更多
Based on the resin bonded sand casting process, the effects of chill processes on the secondary dendrite arm spacing(SDAS) and densification of Al-Si-Mg alloy were studied. The influences of the chill thickness and ef...Based on the resin bonded sand casting process, the effects of chill processes on the secondary dendrite arm spacing(SDAS) and densification of Al-Si-Mg alloy were studied. The influences of the chill thickness and effective distance of chill operating on the SDAS were researched; and the effect of chill heat capacity on SDAS was investigated. The result reveals that, SDAS decreases with increasing the thickness of chill but the effect of chill is finite. The effective distance of chill operating for the chill with different thickness were obtained, and the functional relations among modulus, length of castings and thickness of chill were discussed, and the synthetical network chart of the relation among them was plotted. The relationship between local solidification rate and SDAS was defined by means of quadratic polynomial regression.展开更多
The as-cast Mg-8Li-3Al-0.5Mn-xSr（LAM830-xSr, x=0-1.0） alloys were designed and prepared in a vacuum induction furnace under controlled argon atmosphere. The alloys were then processed by hot extrusion, and their mic...The as-cast Mg-8Li-3Al-0.5Mn-xSr（LAM830-xSr, x=0-1.0） alloys were designed and prepared in a vacuum induction furnace under controlled argon atmosphere. The alloys were then processed by hot extrusion, and their microstructural evolution and mechanical properties were analyzed. Results indicate that the LAM830 alloy mainly consists of α-Mg, β-Li, Al2Mn3, and LiMgAl2 phases. Sr addition results in the precipitation of Al-Sr. Moreover, Sr addition results in a fact that the secondary dendrite arm spacing（DAS） of the primary α-Mg phase is obvious refined. Microstructure of the investigated alloys is further refined as a result of the hot extrusion treatment. The content and morphology of the secondary phases have important effects on the mechanical properties of the alloys. The as-extruded LAM830-0.5Sr alloy exhibits an optimal elongation of 22.43% and as-extruded LAM830-0.75 Sr alloy shows an optimal tensile strength of 265.46 MPa.展开更多
The objective of the work is focused on predictions of microsegregation,solidification speed,dendritic arm spacings and dendrite morphology by phase-field model.The numerical results were compared with experimental da...The objective of the work is focused on predictions of microsegregation,solidification speed,dendritic arm spacings and dendrite morphology by phase-field model.The numerical results were compared with experimental data.The experimental values for cooling rates and effective partition coefficient were adopted during calculations.The results of microsegregation through phase-field model show excellent agreement with the experimental data.Such excellent agreement is because cooling rates,effective partition coefficient and back-diffusion of solute are considered in the model.For solidification speed,the calculation results show good agreement with the experimental data.Tertiary dendritic arm spacing calculated with phase-field model is compared with experimental data.The results show good agreement between them.The dendrite arm spacing varies with position because high cooling rates are responsible for the refinement effect on microstructure.Finally,two-dimensional simulation produced a dendrite that is similar to that found in the experiment.展开更多
For Al-11.6%Si alloy,the influence of the addition of Sr on the morphology of the dendrite α phase was investigated,and the characteristic parameters of the dendrite α phase,the primary dendrite spacing and the seco...For Al-11.6%Si alloy,the influence of the addition of Sr on the morphology of the dendrite α phase was investigated,and the characteristic parameters of the dendrite α phase,the primary dendrite spacing and the secondary dendr ite arm spacing,were also measured. The addition of strontium promotes the colu mnar dendrite growth and leads to a decrease of both the primary dendrite spacin g and secondary dendrite arm spacing with the increase of the content of stronti um in the modified near-eutectic Al-Si alloys. It is thought that the addition of Sr leads to a reduction of the solid-liquid interfacial energy of the dendr ite α phase,consequently resulting in a decrease of the growth undercoolin g of dendrite tips. And hence,the nucleation of the equiaxed grains in the liqu id in front of the columnar dendrite tips is restrained,thus the addition of st rontium in Al-Si alloys promotes the growth of the columnar dendrites. The redu ction of the solid-liquid interfacial energy also leads to the decreases in the primary dendrite spacing and the secondary dendrite arm spacing.展开更多
文摘The influence of pure La, pure Ce, (La+Ce) mischmetal on the dendritical arm space(LDAS) of ZL105 alloy in cylinderical casting was studied. The effects of adding amount of (La+ Ce) mischmetal on LDAs and ultimate tensile strength(b) were investigated, and the relationship between b and LDAS was founded. (La+Ce) mischmetal has stronger ability to refine LDAs than pure La or pure Ce. The proper adding amounts of it is 0.15% (mass fraction). LDAs has a remarkable effect on ah of casting, which can be predicted by the regression equation obtained in this work.
基金Project(0621000700) supported by the Innovation Fund for Outstanding Scholar of Henan Province, China
文摘Based on the resin bonded sand casting process, the effects of chill processes on the secondary dendrite arm spacing(SDAS) and densification of Al-Si-Mg alloy were studied. The influences of the chill thickness and effective distance of chill operating on the SDAS were researched; and the effect of chill heat capacity on SDAS was investigated. The result reveals that, SDAS decreases with increasing the thickness of chill but the effect of chill is finite. The effective distance of chill operating for the chill with different thickness were obtained, and the functional relations among modulus, length of castings and thickness of chill were discussed, and the synthetical network chart of the relation among them was plotted. The relationship between local solidification rate and SDAS was defined by means of quadratic polynomial regression.
基金Project(2007CB613702)supported by the National Basic Research Program of ChinaProject(2008BB4323)supported by the Natural Science Foundation of Chongqing Science and Technology Commission,ChinaProject(2010DFR50010)supported by the International Scientific and Technological Cooperation Projects,China
文摘The as-cast Mg-8Li-3Al-0.5Mn-xSr（LAM830-xSr, x=0-1.0） alloys were designed and prepared in a vacuum induction furnace under controlled argon atmosphere. The alloys were then processed by hot extrusion, and their microstructural evolution and mechanical properties were analyzed. Results indicate that the LAM830 alloy mainly consists of α-Mg, β-Li, Al2Mn3, and LiMgAl2 phases. Sr addition results in the precipitation of Al-Sr. Moreover, Sr addition results in a fact that the secondary dendrite arm spacing（DAS） of the primary α-Mg phase is obvious refined. Microstructure of the investigated alloys is further refined as a result of the hot extrusion treatment. The content and morphology of the secondary phases have important effects on the mechanical properties of the alloys. The as-extruded LAM830-0.5Sr alloy exhibits an optimal elongation of 22.43% and as-extruded LAM830-0.75 Sr alloy shows an optimal tensile strength of 265.46 MPa.
基金FAPERJ(Fundacao de Amparo a Pesquisa do Estado do Rio de Janeiro,APQ#1:E-26/010.001942/2019)CNPq(Conselho Nacional de Desenvolvimento Cientifico e Tecnologico)for their financial support。
文摘The objective of the work is focused on predictions of microsegregation,solidification speed,dendritic arm spacings and dendrite morphology by phase-field model.The numerical results were compared with experimental data.The experimental values for cooling rates and effective partition coefficient were adopted during calculations.The results of microsegregation through phase-field model show excellent agreement with the experimental data.Such excellent agreement is because cooling rates,effective partition coefficient and back-diffusion of solute are considered in the model.For solidification speed,the calculation results show good agreement with the experimental data.Tertiary dendritic arm spacing calculated with phase-field model is compared with experimental data.The results show good agreement between them.The dendrite arm spacing varies with position because high cooling rates are responsible for the refinement effect on microstructure.Finally,two-dimensional simulation produced a dendrite that is similar to that found in the experiment.
文摘For Al-11.6%Si alloy,the influence of the addition of Sr on the morphology of the dendrite α phase was investigated,and the characteristic parameters of the dendrite α phase,the primary dendrite spacing and the secondary dendr ite arm spacing,were also measured. The addition of strontium promotes the colu mnar dendrite growth and leads to a decrease of both the primary dendrite spacin g and secondary dendrite arm spacing with the increase of the content of stronti um in the modified near-eutectic Al-Si alloys. It is thought that the addition of Sr leads to a reduction of the solid-liquid interfacial energy of the dendr ite α phase,consequently resulting in a decrease of the growth undercoolin g of dendrite tips. And hence,the nucleation of the equiaxed grains in the liqu id in front of the columnar dendrite tips is restrained,thus the addition of st rontium in Al-Si alloys promotes the growth of the columnar dendrites. The redu ction of the solid-liquid interfacial energy also leads to the decreases in the primary dendrite spacing and the secondary dendrite arm spacing.
