The effects of a low frequency electromagnetic field and a low frequency electromagnetic vibration field applied during DC casting of AZ80 Mg on microstructures and alloying element distribution in ingots were investi...The effects of a low frequency electromagnetic field and a low frequency electromagnetic vibration field applied during DC casting of AZ80 Mg on microstructures and alloying element distribution in ingots were investigated.The experiments were performed both in absence and in the presence of the magnetic fields.In DC casting,the ingot exhibited coarse microstructure and severe segregation of Al.In the presence of solo low frequency alternating magnetic field,namely LFEC,the grains of the ingot was effectively refined and the segregation of Al was significantly decreased.In LFEVC,namely low frequency electromagnetic vibration casting,the ingot were significantly refined and the segregation was suppressed.With increasing the vibration intensities,the grain refinement and segregation suppression were increased.展开更多
The microstructures after casting and extruding, the mechanical properties and electrical conductivity after RRA treatment of conventional DC casting and low frequency electromagnetic casting （LFEC） 7075 aluminum al...The microstructures after casting and extruding, the mechanical properties and electrical conductivity after RRA treatment of conventional DC casting and low frequency electromagnetic casting （LFEC） 7075 aluminum alloy were investigated. The results showed that finer grains which distributed more homogeneously was obtained in LFEC ingots compared with those conventional DC ingots. The extruded bars of LFEC alloy kept its fine grain features of original as-cast structure. In the RRA treatment, with the extension of second aging time, the tensile strength and hardness of alloy decreased, but the electrical conductivity increased. Meanwhile, as the second aging temperature raised, the phase change rate in precipitation also increased. Under the same conditions, extruded bars of LFEC alloy had better performance than that of conventional DC cast alloy. The optimum RRA heat treatment process was 120 ℃/24 h＋180 ℃/30 min＋120 ℃/24 h. The LFEC extruded bars acquired tensile strength 676.64 MPa, hardness 198.18, and electrical conductivity 35.7% IACS respectively, which were higher than that in the T6 temper, indicating that a notable RRA response takes place in LFEC extruded bars, whose second-step retrogression time was 30 min, and it was suitable for mass production.展开更多
The microstructures of the magnesium billets could be improved markedly by low-frequency electro-magnetic casting (LFEC) processing. In fact, the low-frequency electromagnetic field (LFEF) also has favorite effect on ...The microstructures of the magnesium billets could be improved markedly by low-frequency electro-magnetic casting (LFEC) processing. In fact, the low-frequency electromagnetic field (LFEF) also has favorite effect on the surface quality of billet. However, few public reports on the surface quality of LFEC magnesium billets could be found. Therefore, a new crystallizer with a metal internal sleeve to-gether with a kind of lubricant was designed aiming at lowing surface turning quantity, and the effects of casting velocity, electromagnetic condition and lubrication on the surface quality of magnesium billets were investigated. The results indicate that LFEF together with the lubricate condition would be responsible for the surface quality of the billets, and the high surface quality billets could be achieved by optimizing the casting conditions.展开更多
In this study,the low frequency electromagnetic casting(LFEC) technology was adopted to fabricate 2195 Al-Li alloy.The microstructure and solid solubility of as-cast 2195 alloys,as well as the second phase precipitati...In this study,the low frequency electromagnetic casting(LFEC) technology was adopted to fabricate 2195 Al-Li alloy.The microstructure and solid solubility of as-cast 2195 alloys,as well as the second phase precipitation and tensile properties after aging,were investiagated and compared with the counterpart direct chill casting 2195 alloy.Our results indicate that LFEC can significantly improve the microstructure and metallurgical quality of as-cast alloy,and increase the number density of θ’(Al2Cu) and T1(Al2CuLi) phases during aging treatment due to the enhanced solubilities of alloying elements.The tensile properties of 2195 aged alloy cast by LFEC were hence improved evidently.展开更多
This work explores the microstructure of low frequency electromagnetic casting （LFEC） 7075 aluminum alloys and investigates the effect of heat treatment process on its mechanical properties via the mechanical proper...This work explores the microstructure of low frequency electromagnetic casting （LFEC） 7075 aluminum alloys and investigates the effect of heat treatment process on its mechanical properties via the mechanical properties test, X-ray diffraction and transmission electron microscopy. It was found that the grains of LFEC ingot were finer and more evenly distributed than that of the conventional direct chill cast （DC） ingots. The microstructure of LFEC ingot extruded kept their original as-cast struc- ture with small and fine grains. With the same extrusion ratio, the average grain diameters of LFEC and conventional DC extruded were about 10 and 20 #m, re- spectively. LFEC extruded also had a better aging property, since the regime of T6 treatment peak value aging was at 120 ~C for 24 h, the tensile strength and hardness （HV） of the LFEC extruded were 673.50 MPa and 194.62, respectively, which were all higher than those of the conventional DC extruded, indicating that the process regime can be applied in the industrial production.展开更多
The magnetic field interference was studied by numerical simulation and experimental examination during dual-ingot low-frequency electromagnetic casting process.By using ANSYS software package to mesh and compute,the ...The magnetic field interference was studied by numerical simulation and experimental examination during dual-ingot low-frequency electromagnetic casting process.By using ANSYS software package to mesh and compute,the magnetic field distribution of semi-continuous casting mold region was simulated.The calculated results were verified with the experimental ones and the effects of current direction,shield,silicon sheet and the coil distance on the distribution of magnetic field and ingot were observed.The result indicated that:regardless of current direction,the magnetic field interference among coils appears and the magnetic flux density weakens in the neighbor part of coils. When the current direction of adjacent coils is opposite,the magnetic intensity in ingots is stronger than that of in the same direction.As the distance between coils increases,the magnetic field reduction generated by interference decreases. The magnetic field interference can be alleviated by setting silicon steel sheets or shield.展开更多
基金This work is financially supported by the Emphasis Project Fund of National Eleven Five-Year Scientific and Technical Support Plans ( No 2006BAE04B02)the National Natural Science Foundation of Chi-na ( No 50574028)+1 种基金the Programme of Introducing Talents of Discipline to Universities(No B07015) the Cultivation Fund of the Key Scientific and Technical Innovation Project,Ministry of Education of China(No 704015)
文摘The effects of a low frequency electromagnetic field and a low frequency electromagnetic vibration field applied during DC casting of AZ80 Mg on microstructures and alloying element distribution in ingots were investigated.The experiments were performed both in absence and in the presence of the magnetic fields.In DC casting,the ingot exhibited coarse microstructure and severe segregation of Al.In the presence of solo low frequency alternating magnetic field,namely LFEC,the grains of the ingot was effectively refined and the segregation of Al was significantly decreased.In LFEVC,namely low frequency electromagnetic vibration casting,the ingot were significantly refined and the segregation was suppressed.With increasing the vibration intensities,the grain refinement and segregation suppression were increased.
基金Funded by the National Natural Science Foundation of China(Nos. 51004036 and N110408005)
文摘The microstructures after casting and extruding, the mechanical properties and electrical conductivity after RRA treatment of conventional DC casting and low frequency electromagnetic casting （LFEC） 7075 aluminum alloy were investigated. The results showed that finer grains which distributed more homogeneously was obtained in LFEC ingots compared with those conventional DC ingots. The extruded bars of LFEC alloy kept its fine grain features of original as-cast structure. In the RRA treatment, with the extension of second aging time, the tensile strength and hardness of alloy decreased, but the electrical conductivity increased. Meanwhile, as the second aging temperature raised, the phase change rate in precipitation also increased. Under the same conditions, extruded bars of LFEC alloy had better performance than that of conventional DC cast alloy. The optimum RRA heat treatment process was 120 ℃/24 h＋180 ℃/30 min＋120 ℃/24 h. The LFEC extruded bars acquired tensile strength 676.64 MPa, hardness 198.18, and electrical conductivity 35.7% IACS respectively, which were higher than that in the T6 temper, indicating that a notable RRA response takes place in LFEC extruded bars, whose second-step retrogression time was 30 min, and it was suitable for mass production.
基金Supported by the 11th Five-Year Plan of China (Grant No. 2006BAE04B01-5)the National Basic Research Program of China ("973") (Grant No. 2007CB613702)
文摘The microstructures of the magnesium billets could be improved markedly by low-frequency electro-magnetic casting (LFEC) processing. In fact, the low-frequency electromagnetic field (LFEF) also has favorite effect on the surface quality of billet. However, few public reports on the surface quality of LFEC magnesium billets could be found. Therefore, a new crystallizer with a metal internal sleeve to-gether with a kind of lubricant was designed aiming at lowing surface turning quantity, and the effects of casting velocity, electromagnetic condition and lubrication on the surface quality of magnesium billets were investigated. The results indicate that LFEF together with the lubricate condition would be responsible for the surface quality of the billets, and the high surface quality billets could be achieved by optimizing the casting conditions.
基金supported by the National Key Research and Development Program of China (No. 2016YFB0300901)the National Natural Science Foundation of China (Nos. U1708251, 51574075, U1608252)+1 种基金the Liaoning Revitalization Talents Program (No. XLYC1807027)the Fundamental Research Funds for the Central Universities (No. N180905010).
文摘In this study,the low frequency electromagnetic casting(LFEC) technology was adopted to fabricate 2195 Al-Li alloy.The microstructure and solid solubility of as-cast 2195 alloys,as well as the second phase precipitation and tensile properties after aging,were investiagated and compared with the counterpart direct chill casting 2195 alloy.Our results indicate that LFEC can significantly improve the microstructure and metallurgical quality of as-cast alloy,and increase the number density of θ’(Al2Cu) and T1(Al2CuLi) phases during aging treatment due to the enhanced solubilities of alloying elements.The tensile properties of 2195 aged alloy cast by LFEC were hence improved evidently.
基金supported by the National Natural Science Foundation of China (Youth)(No.51004036)the Fundamental Research Funds (No. N110408005)
文摘This work explores the microstructure of low frequency electromagnetic casting （LFEC） 7075 aluminum alloys and investigates the effect of heat treatment process on its mechanical properties via the mechanical properties test, X-ray diffraction and transmission electron microscopy. It was found that the grains of LFEC ingot were finer and more evenly distributed than that of the conventional direct chill cast （DC） ingots. The microstructure of LFEC ingot extruded kept their original as-cast struc- ture with small and fine grains. With the same extrusion ratio, the average grain diameters of LFEC and conventional DC extruded were about 10 and 20 #m, re- spectively. LFEC extruded also had a better aging property, since the regime of T6 treatment peak value aging was at 120 ~C for 24 h, the tensile strength and hardness （HV） of the LFEC extruded were 673.50 MPa and 194.62, respectively, which were all higher than those of the conventional DC extruded, indicating that the process regime can be applied in the industrial production.
基金Item Sponsored by National Natural Science Foundation of China(youth)[No.51004036]the Fundamental Research Funds[N110408005]
文摘The magnetic field interference was studied by numerical simulation and experimental examination during dual-ingot low-frequency electromagnetic casting process.By using ANSYS software package to mesh and compute,the magnetic field distribution of semi-continuous casting mold region was simulated.The calculated results were verified with the experimental ones and the effects of current direction,shield,silicon sheet and the coil distance on the distribution of magnetic field and ingot were observed.The result indicated that:regardless of current direction,the magnetic field interference among coils appears and the magnetic flux density weakens in the neighbor part of coils. When the current direction of adjacent coils is opposite,the magnetic intensity in ingots is stronger than that of in the same direction.As the distance between coils increases,the magnetic field reduction generated by interference decreases. The magnetic field interference can be alleviated by setting silicon steel sheets or shield.
