The rapid development of magnetic materials provides the possibility for the application of permanent magnet stirring(PMS).Numerical and experimental investigations were employed with respect to the solidification pro...The rapid development of magnetic materials provides the possibility for the application of permanent magnet stirring(PMS).Numerical and experimental investigations were employed with respect to the solidification process of the Al—2Sc alloy controlled by a novel PMS using NdFeB permanent magnets under various rotation speeds(0,50,100 and 150 r/min).The simulated results reveal that the maximum electromagnetic force increases proportionally from 4.14 to 12.39 kN/m^(3)and the maximum tangential velocity increases from 0.13 to 0.36 m/s when the rotation speed of PMS enhances from 50 to 150 r/min in the ingot melt.Besides,the experimental results demonstrate that PMS can achieve a uniform distribution of blocky Al_(3)Sc precipitated phase in the longitudinal direction under the impact of a forced fluid flow.Moreover,increasing rotation speed of PMS is beneficial to refining aluminum grain size significantly and decreasing the texture intensity in the alloy.In addition,the Brinell hardness of Al-2Sc alloy is increased by 33%to 27.8 HB and the tensile strength is enhanced by 34%-128.2 MPa,due to the improved distribution of the strengthening Al_(3)SC phase and the grain refinement of Al matrix under the impact of PMS.This work provides an effective application of NdFeB permanent magnets in the metal cast field.展开更多
Nearly undamaged joints of electron beam welded(EBW)dual-phase Mg-8Li-3Al-2Zn-0.5Y alloy were achieved with joint coefficients exceeding 95%.All specimens were fractured at the base metal(BM),implying a significant de...Nearly undamaged joints of electron beam welded(EBW)dual-phase Mg-8Li-3Al-2Zn-0.5Y alloy were achieved with joint coefficients exceeding 95%.All specimens were fractured at the base metal(BM),implying a significant departure from conventional fracture modes of welded joints.The fusion zone(FZ)consists of ultrafine acicular α-Mg and equiaxed β-Li,with grain sizes reduced by approximately 90% and 80%,respectively,compared to the base metal.This results in a significant increase in microhardness of about 40%.A unique multiphase mixture was observed in the heat-affected zone(HAZ),which mainly consists of lamellar eutectoid structures,fine precipitates zone,and numerous fine Mg_(3)(Al,Zn)particles.This mixture was transformed from typical Li(Al,Zn)(a common softening phase)undergoing atomic diffusion and solid-state phase transformation during welding.It introduces a synergistic strengthening effect,making the heat-affected zone no longer the weakest part of the joint.This study provides valuable insights into the electron beam welding technology for Mg-Li alloys and offers theoretical support for manufacturing high-quality joints.展开更多
Ti-2Al-2.5Zr is widely used in piping and structural support applications,however,the rolling forming process results in anisotropic deformation during service.This behavior has implications for the manu-facturing pro...Ti-2Al-2.5Zr is widely used in piping and structural support applications,however,the rolling forming process results in anisotropic deformation during service.This behavior has implications for the manu-facturing processes and structural safety assessments in engineering applications.In this study,the plas-tic anisotropic deformation behavior of a rolled Ti-2Al-2.5Zr plate was investigated using uniaxial tensile tests along the transverse,normal,and 45°directions.Acoustic emission,electron backscatter diffraction,and scanning electron microscopy methods were used to investigate dislocation slip and twinning mech-anisms.The results indicated that different microscopic deformation mechanisms caused the significant macroscopic anisotropy of Ti-2Al-2.5Zr.The primary mechanisms involved were prismaticslip,pyra-midal<c+a>slip,and{10-12}extension twinning.The stress direction determined the influence of each of these mechanisms during the yielding and plastic deformation phases.Application of the visco-plastic self-consistent model established the relationship between the macroscopic mechanical responses and microscopic deformation mechanisms.It was revealed that Ti-2Al-2.5Zr achieved its optimum strength when the initial texture aligned most of the grain c-axis at angles ranging from 30°to 50°relative to the deformation direction.This finding provides a direction for the texture design of Ti-2Al-2.5Zr in engineer-ing materials.展开更多
基金Project supported by the Natural Science Foundation of Hunan Province(2024JJ4056)the Key Project of Guangxi Zhuang Autonomous Region(AB22080089)the Government of Chongzuo,Guangxi Zhuang Autonomous Region(FA20210716)。
文摘The rapid development of magnetic materials provides the possibility for the application of permanent magnet stirring(PMS).Numerical and experimental investigations were employed with respect to the solidification process of the Al—2Sc alloy controlled by a novel PMS using NdFeB permanent magnets under various rotation speeds(0,50,100 and 150 r/min).The simulated results reveal that the maximum electromagnetic force increases proportionally from 4.14 to 12.39 kN/m^(3)and the maximum tangential velocity increases from 0.13 to 0.36 m/s when the rotation speed of PMS enhances from 50 to 150 r/min in the ingot melt.Besides,the experimental results demonstrate that PMS can achieve a uniform distribution of blocky Al_(3)Sc precipitated phase in the longitudinal direction under the impact of a forced fluid flow.Moreover,increasing rotation speed of PMS is beneficial to refining aluminum grain size significantly and decreasing the texture intensity in the alloy.In addition,the Brinell hardness of Al-2Sc alloy is increased by 33%to 27.8 HB and the tensile strength is enhanced by 34%-128.2 MPa,due to the improved distribution of the strengthening Al_(3)SC phase and the grain refinement of Al matrix under the impact of PMS.This work provides an effective application of NdFeB permanent magnets in the metal cast field.
基金financially supported by the National Defense Basic Research Program(No.JCKY2023204A005)Project of High Modulus Magnesium Alloy Forgings(JXXT-2023-014hbza)+1 种基金Research Program of Joint Research Center of Advanced Spaceflight Technologies(No.USCAST2023-3)Major Scientific and Technological Innovation Project of Luoyang(No.2201029A).
文摘Nearly undamaged joints of electron beam welded(EBW)dual-phase Mg-8Li-3Al-2Zn-0.5Y alloy were achieved with joint coefficients exceeding 95%.All specimens were fractured at the base metal(BM),implying a significant departure from conventional fracture modes of welded joints.The fusion zone(FZ)consists of ultrafine acicular α-Mg and equiaxed β-Li,with grain sizes reduced by approximately 90% and 80%,respectively,compared to the base metal.This results in a significant increase in microhardness of about 40%.A unique multiphase mixture was observed in the heat-affected zone(HAZ),which mainly consists of lamellar eutectoid structures,fine precipitates zone,and numerous fine Mg_(3)(Al,Zn)particles.This mixture was transformed from typical Li(Al,Zn)(a common softening phase)undergoing atomic diffusion and solid-state phase transformation during welding.It introduces a synergistic strengthening effect,making the heat-affected zone no longer the weakest part of the joint.This study provides valuable insights into the electron beam welding technology for Mg-Li alloys and offers theoretical support for manufacturing high-quality joints.
基金support from the National Key R&D Program of China(No.2020YFA0405901)the National Natural Science Foundation of China(Nos.52375155 and 51875398)+1 种基金the Science and Technology on Reactor Fuel and Materials Laboratory(No.6142A06040202)the Nuclear Power Institute of China.
文摘Ti-2Al-2.5Zr is widely used in piping and structural support applications,however,the rolling forming process results in anisotropic deformation during service.This behavior has implications for the manu-facturing processes and structural safety assessments in engineering applications.In this study,the plas-tic anisotropic deformation behavior of a rolled Ti-2Al-2.5Zr plate was investigated using uniaxial tensile tests along the transverse,normal,and 45°directions.Acoustic emission,electron backscatter diffraction,and scanning electron microscopy methods were used to investigate dislocation slip and twinning mech-anisms.The results indicated that different microscopic deformation mechanisms caused the significant macroscopic anisotropy of Ti-2Al-2.5Zr.The primary mechanisms involved were prismaticslip,pyra-midal<c+a>slip,and{10-12}extension twinning.The stress direction determined the influence of each of these mechanisms during the yielding and plastic deformation phases.Application of the visco-plastic self-consistent model established the relationship between the macroscopic mechanical responses and microscopic deformation mechanisms.It was revealed that Ti-2Al-2.5Zr achieved its optimum strength when the initial texture aligned most of the grain c-axis at angles ranging from 30°to 50°relative to the deformation direction.This finding provides a direction for the texture design of Ti-2Al-2.5Zr in engineer-ing materials.
