New strain induced melt activated (new SIMA) method for preparing AZ91D magnesium alloy semi-solid billet is introduced by applying equal channel angular extrusion into strain induced step in SIMA method, by which sem...New strain induced melt activated (new SIMA) method for preparing AZ91D magnesium alloy semi-solid billet is introduced by applying equal channel angular extrusion into strain induced step in SIMA method, by which semi-solid billet with fine spheroidal grains and average grain size of 18 μm can be prepared. Furthermore, average grain size of semi-solid billet is reduced with increasing extrusion pass of AZ91D magnesium alloy obtained in ECAE process. By using semi-solid billet prepared by new SIMA, thixoforged magazine plates component with high mechanical properties such as yield strength of 201.4 MPa, ultimate tensile strength of 321.8 MPa and elongation of 15.3%, can be obtained.展开更多
The effects of Al-8B grain refiner on microstructure and tensile properties of an Al-12Zn-3Mg-2.5Cu alloy produced by modified strain induced melt activation process were investigated. Pre-deformation of 60% was used ...The effects of Al-8B grain refiner on microstructure and tensile properties of an Al-12Zn-3Mg-2.5Cu alloy produced by modified strain induced melt activation process were investigated. Pre-deformation of 60% was used by hot working at 300 ℃. After pre-deformation, the samples were heated to a temperature above the solidus and below the liquidus point and maintained in the isothermal conditions at three different temperatures（500, 550 and 590 ℃） for varying time（10, 20 and 40 min）. It was observed that strain induced melt activation has caused the globular morphology of α（Al） grains. Microstructural study was carried out on the alloy by using optical microscope and scanning electron microscope in both unrefined and B-refined conditions. The results showed that for the desired microstructures of the alloy during SIMA process, the optimum temperature and time are 550 ℃ and 10 min, respectively. After the T6 heat treatment, the average tensile strengths increased from 278 to 585 MPa and 252 to 560 MPa for samples refined with 3.75% Al-8B before and after SIMA process, respectively. The ultimate strength of SIMA specimens is lower than that of B-refined specimens.展开更多
Structure evolution of an Al-Zn wrought alloy in remelting processing in thestrain induced melt activated (SIMA) serai-solid procedure was observed, and effects of factors, theremelting temperature, the holding time, ...Structure evolution of an Al-Zn wrought alloy in remelting processing in thestrain induced melt activated (SIMA) serai-solid procedure was observed, and effects of factors, theremelting temperature, the holding time, and the compression strain, on structures and grain sizesof the alloy were investigated. The results show that (1) the proper temperature of remelting is inthe range of 610 to 615℃; (2) the grain size in specimen with greater compression strain is smallerthan that with smaller compression strain in condition of the same remelting temperature andholding time, and the grain size in local area with great local equivalent strain is smaller thanthat with small one; (3) liquid occurs in form of cluster in matrix during remelting and itsquantity increases with remelting time increasing; liquid in specimen with great compression strainoccurs earlier than that with small one, and quantity of liquid in the center of specimen withgreater local equivalent strain is greater than that in the two ends of it; (4) distortion energyafter deforming in matrix of the alloy is the significant factor to activate melting of matrix atlocal area with great local equivalent strain.展开更多
AZ91D magnesium alloy chips were adopted to prepare semi-solid billets.The chips were subjected to a series ofisothermal treatments for various holding times at 783?843 K after being compressed into billet at 523 K.Th...AZ91D magnesium alloy chips were adopted to prepare semi-solid billets.The chips were subjected to a series ofisothermal treatments for various holding times at 783?843 K after being compressed into billet at 523 K.The semi-solid microstructure of AZ91D magnesium alloy containing spherical solid particles was studied.The effects of reheating temperature and holding time on microstructures were investigated.And the semi-solid forming mechanism was discussed.The result shows that semi-solid billets with highly spheroidal and homogeneous grains can be prepared from chips by strain induced melt activation(SIMA) method.Meanwhile,it is found that increasing the heating temperature can accelerate the spheroidizing process and reduce the solid volume fraction.With the increase of the holding time,the solid particles become more globular,the grains grow slowly and the solid volume fraction slightly changes.At the same time,owing to the decrease ofinterfacial energy,the intragranular liquid phases form by the diffusion of solute atoms,the grain boundaries melt and grains separate from each other during the isothermal treatment.The grains gradually spheroidize and begin to merge with a further increase of the holding time.It is considered that the semi-solid forming process includes three stages:the recrystallization and the growth of grain stage,the semi-solid microstructure forming stage controlled by the diffusion of solute,and the spheroidization of solid particle stage controlled by the liquid-solid interface tension.展开更多
A semi-solid microstructure of ADC12 aluminum alloy containing spherical solid particles was studied.A new strain-induced melt activation(SIMA) process was proposed.In the treatment,chips were cut from ADC12 ingot by ...A semi-solid microstructure of ADC12 aluminum alloy containing spherical solid particles was studied.A new strain-induced melt activation(SIMA) process was proposed.In the treatment,chips were cut from ADC12 ingot by lathe machining and the plastic deformation was produced through cutting.The chips were put into a metal mold and compressed into a billet at 473 K.The microstructures of chip and billet were studied.The effect of the isothermal treatment on the semi-solid microstructure evolution of ADC12 aluminum alloy prepared by the new method was analyzed.A series of heating treatments were carried out from 823 to 838 K.The effects of heating temperature on microstructures were studied.The experimental results show the ADC12 aluminum alloy prepared by the new method can reap homogeneous and spherical grains at 828 K.The average grain size is about 82 μm.Also,the grain microstructure obtained by the present process is better than the traditional one.These results prove that the ADC12 aluminum alloy can be applied to semi-solid processing with the new SIMA method.展开更多
Based on SIMA, the Al-Si alloy semi-solid billets were successfully fabricated by means of strain inducement and isothermal treatment for AlSi9Mg poured in the range of near-liquidus. Through orthogonal test, the effe...Based on SIMA, the Al-Si alloy semi-solid billets were successfully fabricated by means of strain inducement and isothermal treatment for AlSi9Mg poured in the range of near-liquidus. Through orthogonal test, the effects of combination action of near-liquidus casting, strain inducement and isothermal treatment on the morphology of primaryα-Al phase of AlSi9Mg close to eutectic point were investigated, and the optimal match relation between the processing parameters of solidification, deformation parameters of strain inducement, processing parameters of isothermal treatment and microstructure parameters of semi-solid alloy was established. The results indicate that compared with the single near-liquidus casting or SIMA, the microstructure of primaryα-Al phase in AlSi9Mg alloy prepared by compound fabrication process is more homogeneous, with more globular and finer particles, which has average grain size of 40-50 urn and shape factor of greater than 0.75. After holding at 605℃for 30-40 min under a certain cooling rate, increased deformation volume in SIMA benefits the refinement of the grain and the improvement of the morphology for primary phase.展开更多
New strain induced melt activation（new SIMA） method was employed to prepare high-quality semisolid billet of AZ61 magnesium alloy.Optical microscopy and tensile test were used to study the microstructure and mechani...New strain induced melt activation（new SIMA） method was employed to prepare high-quality semisolid billet of AZ61 magnesium alloy.Optical microscopy and tensile test were used to study the microstructure and mechanical properties of the thixo-extruded component.The results showed that the optimal process parameters for achieving the complete filling status involved the applied pressure of 784 MPa,the pressure holding time of 90 s and the die temperature of 450 ℃.Compared to semisolid isothermal treatment,high mechanical properties such as the tensile strength of 300.5 MPa and elongation of 22% and fine microstructure were obtained in the thixo-extruded parts.With increasing the isothermal temperature and holding time,the tensile strength and elongation were increased firstly and then decreased.When the press pass was increased from 1 to 4,the tensile strength and elongation of the thixo-extruded parts were greatly enhanced and microstructure was refined obviously.展开更多
A new Mg−10%Al−1%Zn−1%Si alloy with non-dendritic microstructure was prepared by strain induced melt activation(SIMA)process.The effect of compression ratio on the evolution of semisolid microstructure of the experime...A new Mg−10%Al−1%Zn−1%Si alloy with non-dendritic microstructure was prepared by strain induced melt activation(SIMA)process.The effect of compression ratio on the evolution of semisolid microstructure of the experimental alloy was investigated.The results indicate that the average size ofα-Mg grains decreases and spheroidizing tendency becomes more obvious with the compression ratios increasing from 0 to 40%.In addition,the eutectic Mg2Si phase in the Mg−10%Al−1%Zn−1%Si alloy transforms completely from the initial fishbone shape to globular shape by SIMA process.With the increasing of compression ratio,the morphology and average size of Mg2Si phases do not change obviously.The morphology modification mechanism of Mg2Si phase in Mg−10%Al−1%Zn−1%Si alloy by SIMA process was also studied.展开更多
基金Project(50475029, 50605015) supported by the National Natural Science Foundation of China
文摘New strain induced melt activated (new SIMA) method for preparing AZ91D magnesium alloy semi-solid billet is introduced by applying equal channel angular extrusion into strain induced step in SIMA method, by which semi-solid billet with fine spheroidal grains and average grain size of 18 μm can be prepared. Furthermore, average grain size of semi-solid billet is reduced with increasing extrusion pass of AZ91D magnesium alloy obtained in ECAE process. By using semi-solid billet prepared by new SIMA, thixoforged magazine plates component with high mechanical properties such as yield strength of 201.4 MPa, ultimate tensile strength of 321.8 MPa and elongation of 15.3%, can be obtained.
文摘The effects of Al-8B grain refiner on microstructure and tensile properties of an Al-12Zn-3Mg-2.5Cu alloy produced by modified strain induced melt activation process were investigated. Pre-deformation of 60% was used by hot working at 300 ℃. After pre-deformation, the samples were heated to a temperature above the solidus and below the liquidus point and maintained in the isothermal conditions at three different temperatures（500, 550 and 590 ℃） for varying time（10, 20 and 40 min）. It was observed that strain induced melt activation has caused the globular morphology of α（Al） grains. Microstructural study was carried out on the alloy by using optical microscope and scanning electron microscope in both unrefined and B-refined conditions. The results showed that for the desired microstructures of the alloy during SIMA process, the optimum temperature and time are 550 ℃ and 10 min, respectively. After the T6 heat treatment, the average tensile strengths increased from 278 to 585 MPa and 252 to 560 MPa for samples refined with 3.75% Al-8B before and after SIMA process, respectively. The ultimate strength of SIMA specimens is lower than that of B-refined specimens.
文摘Structure evolution of an Al-Zn wrought alloy in remelting processing in thestrain induced melt activated (SIMA) serai-solid procedure was observed, and effects of factors, theremelting temperature, the holding time, and the compression strain, on structures and grain sizesof the alloy were investigated. The results show that (1) the proper temperature of remelting is inthe range of 610 to 615℃; (2) the grain size in specimen with greater compression strain is smallerthan that with smaller compression strain in condition of the same remelting temperature andholding time, and the grain size in local area with great local equivalent strain is smaller thanthat with small one; (3) liquid occurs in form of cluster in matrix during remelting and itsquantity increases with remelting time increasing; liquid in specimen with great compression strainoccurs earlier than that with small one, and quantity of liquid in the center of specimen withgreater local equivalent strain is greater than that in the two ends of it; (4) distortion energyafter deforming in matrix of the alloy is the significant factor to activate melting of matrix atlocal area with great local equivalent strain.
文摘AZ91D magnesium alloy chips were adopted to prepare semi-solid billets.The chips were subjected to a series ofisothermal treatments for various holding times at 783?843 K after being compressed into billet at 523 K.The semi-solid microstructure of AZ91D magnesium alloy containing spherical solid particles was studied.The effects of reheating temperature and holding time on microstructures were investigated.And the semi-solid forming mechanism was discussed.The result shows that semi-solid billets with highly spheroidal and homogeneous grains can be prepared from chips by strain induced melt activation(SIMA) method.Meanwhile,it is found that increasing the heating temperature can accelerate the spheroidizing process and reduce the solid volume fraction.With the increase of the holding time,the solid particles become more globular,the grains grow slowly and the solid volume fraction slightly changes.At the same time,owing to the decrease ofinterfacial energy,the intragranular liquid phases form by the diffusion of solute atoms,the grain boundaries melt and grains separate from each other during the isothermal treatment.The grains gradually spheroidize and begin to merge with a further increase of the holding time.It is considered that the semi-solid forming process includes three stages:the recrystallization and the growth of grain stage,the semi-solid microstructure forming stage controlled by the diffusion of solute,and the spheroidization of solid particle stage controlled by the liquid-solid interface tension.
基金Project(GB09A202) supported by the Key Project of Science and Technology of Heilongjiang Province,China
文摘A semi-solid microstructure of ADC12 aluminum alloy containing spherical solid particles was studied.A new strain-induced melt activation(SIMA) process was proposed.In the treatment,chips were cut from ADC12 ingot by lathe machining and the plastic deformation was produced through cutting.The chips were put into a metal mold and compressed into a billet at 473 K.The microstructures of chip and billet were studied.The effect of the isothermal treatment on the semi-solid microstructure evolution of ADC12 aluminum alloy prepared by the new method was analyzed.A series of heating treatments were carried out from 823 to 838 K.The effects of heating temperature on microstructures were studied.The experimental results show the ADC12 aluminum alloy prepared by the new method can reap homogeneous and spherical grains at 828 K.The average grain size is about 82 μm.Also,the grain microstructure obtained by the present process is better than the traditional one.These results prove that the ADC12 aluminum alloy can be applied to semi-solid processing with the new SIMA method.
基金Project(04044058) supported by the Excellent Youths Science and Technology Foundation of Anhui, China
文摘Based on SIMA, the Al-Si alloy semi-solid billets were successfully fabricated by means of strain inducement and isothermal treatment for AlSi9Mg poured in the range of near-liquidus. Through orthogonal test, the effects of combination action of near-liquidus casting, strain inducement and isothermal treatment on the morphology of primaryα-Al phase of AlSi9Mg close to eutectic point were investigated, and the optimal match relation between the processing parameters of solidification, deformation parameters of strain inducement, processing parameters of isothermal treatment and microstructure parameters of semi-solid alloy was established. The results indicate that compared with the single near-liquidus casting or SIMA, the microstructure of primaryα-Al phase in AlSi9Mg alloy prepared by compound fabrication process is more homogeneous, with more globular and finer particles, which has average grain size of 40-50 urn and shape factor of greater than 0.75. After holding at 605℃for 30-40 min under a certain cooling rate, increased deformation volume in SIMA benefits the refinement of the grain and the improvement of the morphology for primary phase.
基金Project(51075099) supported by the National Natural Science Foundation of ChinaProject(E201038) supported by the Natural Science Foundation of Heilongjiang Province,China+3 种基金Project(20090460884) supported by the China Postdoctoral Science FoundationProjects (HIT.NSRIF.2013007 and 2012038) supported by the Fundamental Research Funds for the Central Universities,ChinaProject (2011RFQXG010) supported by the Harbin City Young Scientists Foundation under the GrantProject(LBH-T1102) supported by the Specially Postdoctoral Science Foundation of Heilongjiang Province,China
文摘New strain induced melt activation（new SIMA） method was employed to prepare high-quality semisolid billet of AZ61 magnesium alloy.Optical microscopy and tensile test were used to study the microstructure and mechanical properties of the thixo-extruded component.The results showed that the optimal process parameters for achieving the complete filling status involved the applied pressure of 784 MPa,the pressure holding time of 90 s and the die temperature of 450 ℃.Compared to semisolid isothermal treatment,high mechanical properties such as the tensile strength of 300.5 MPa and elongation of 22% and fine microstructure were obtained in the thixo-extruded parts.With increasing the isothermal temperature and holding time,the tensile strength and elongation were increased firstly and then decreased.When the press pass was increased from 1 to 4,the tensile strength and elongation of the thixo-extruded parts were greatly enhanced and microstructure was refined obviously.
基金Project (51075099) supported by the National Natural Science Foundation of ChinaProject (E201038) supported by the Natural Science Foundation of the Heilongjiang Province, China+2 种基金Project (HIT.NSRIF.2013007) supported by the Fundamental Research Funds for the Central Universities, ChinaProject (2011RFQXG010) supported by the Harbin City Young Scientists Foundation, ChinaProject(LBH-T1102) supported by Specially Postdoctoral Science Foundation of Heilongjiang Province, China
基金The authors are grateful for the financial supports from the National Natural Science Foundation of China(Nos.41807235,50674038).
文摘A new Mg−10%Al−1%Zn−1%Si alloy with non-dendritic microstructure was prepared by strain induced melt activation(SIMA)process.The effect of compression ratio on the evolution of semisolid microstructure of the experimental alloy was investigated.The results indicate that the average size ofα-Mg grains decreases and spheroidizing tendency becomes more obvious with the compression ratios increasing from 0 to 40%.In addition,the eutectic Mg2Si phase in the Mg−10%Al−1%Zn−1%Si alloy transforms completely from the initial fishbone shape to globular shape by SIMA process.With the increasing of compression ratio,the morphology and average size of Mg2Si phases do not change obviously.The morphology modification mechanism of Mg2Si phase in Mg−10%Al−1%Zn−1%Si alloy by SIMA process was also studied.
