The effects of semi-solid isothermal process parameters on the microstructure evolution of Mg-Gd rare earth alloy produced by strain-induced melt activation(SIMA)were investigated.The formation mechanism of the partic...The effects of semi-solid isothermal process parameters on the microstructure evolution of Mg-Gd rare earth alloy produced by strain-induced melt activation(SIMA)were investigated.The formation mechanism of the particles in the process of the isothermal treatment was also discussed.The results show that the microstructure of the as-cast alloy consists ofα-Mg solid solution, Mg5RE and Mg24RE5(Gd,Y,Nd)phase.After being extruded with an extrusion ratio of 14:1 at 380℃,the microstructure of Mg-Gd alloy changes from developed dendrites to near-equiaxed grains.The liquid volume fraction of the semisolid slurry gradually increases with elevating isothermal temperature or prolonging isothermal time during the partial remelting.To obtain an ideal semisolid slurry,the optimal process parameters for the Mg-Gd alloy should be 630℃for isothermal temperature and 30 min for the corresponding time,respectively,where the volume fraction of the liquid phase is 52%.展开更多
It is economically advantageous to cast wrought aluminum alloys directly into near-net-shape components.The objective of the present work is to take advantage of the rheoforming with 7075 alloy to improve the competit...It is economically advantageous to cast wrought aluminum alloys directly into near-net-shape components.The objective of the present work is to take advantage of the rheoforming with 7075 alloy to improve the competitiveness of this emerging technology in the manufacture of wrought aluminum alloy.High quality semi-solid slurry was produced,in which primary α(Al) presents in diameter of 62 μm and shape factor of 0.78 and features no eutectics entrapped.Higher forming pressure results in small grain size,improved shape factor and higher density.Especially,rheoforming can effectively reduce the occurrence of hot tearing.The average yield strength and elongation of the rheoformed samples in the T6 condition are 483 MPa and 8%,respectively.展开更多
A new testing procedure to estimate the low-temperature stiffness of the reclaimed asphalt pavement （RAP） binder was developed. In the testing procedure, the SuperpaveTM Bending Beam Rheometer （BBR） with special m...A new testing procedure to estimate the low-temperature stiffness of the reclaimed asphalt pavement （RAP） binder was developed. In the testing procedure, the SuperpaveTM Bending Beam Rheometer （BBR） with special modifications and binder blending charts by Asphalt Institute were utilized. Modifications involved the development of a new kind of sample mold and different testing parameters were made to BBR testing procedure to capture the theological properties of bitumen mortars produced by mixing fresh binder with fine RAP materials or RAP aggregate. The stiffness relationship between binder and bitumen mortar was established based on the BBR test results. The blended binder stiffness in bitumen RAP mortar was estimated from the RAP mortar stiffness based on the binder-mortar relationship. And finally, the RAP binder stiffness was estimated from the blended binder and fresh binder stiffness based on the blending charts by Asphalt Institute. The results indicate that the new procedure can capture the rheological properties of bitumen mortar and can be used to estimate the low temperature stiffness of RAP binder without binder extraction and/or any chemical treatments.展开更多
Semi-solid metal processing is being developed in die casting applications to give several cost benefits. To efficiently apply this emerging technology, it is important to understand the evolution of microstructure in...Semi-solid metal processing is being developed in die casting applications to give several cost benefits. To efficiently apply this emerging technology, it is important to understand the evolution of microstructure in semi-solid slurries for the control of the theological behavior in semi-solid state. An experimental apparatus was developed which can capture the grain structure at different times at early stages to understand how the semi-solid structure evolves. In this technique, semi-solid slurry was produced by injecting fine gas bubbles into the melt through a graphite diffuser during solidification. Then, a copper quenching mold was used to draw some semi-solid slurry into a thin channel. The semi-solid slurry was then rapidly frozen in the channel giving the microstructure of the slurry at the desired time. Samples of semi-solid 356 aluminum alloy were taken at different gas injection times of 1, 5, 10, 15, 20, 30, 35, 40, and 45 s. Analysis of the microstructure suggests that the fragmentation by remelting mechanism should be responsible for the formation of globular structure in this rheocasting process.展开更多
The aim of this study was to analyze the point mutation of the exon 1 at codon 54 of the mannose (or mannan)-binding lectin (MBL) gene in healthy individuals of Chinese Hans and Mongolian population, and to find out a...The aim of this study was to analyze the point mutation of the exon 1 at codon 54 of the mannose (or mannan)-binding lectin (MBL) gene in healthy individuals of Chinese Hans and Mongolian population, and to find out any association between the plasma levels of MBL and the gene mutation frequency in both groups of individuals. Blood samples were collected randomly from 56 healthy individuals of Chinese Hans and 37 Mongolian. The detection of the point mutations of the MBL gene was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and detections for plasma levels of MBL were determined by using MBL ELISA kits. A MBL PCR method of assay was established with high specificity, and good reproducibility. By optimizing the PCR condition, the optimal annealing temperature was 55℃, and the lowest detection limit was 160 pg. No bands were found in non-specificity samples (HAV, HBV, HCV and TB), and the sequences of PCR products were the same as the expected ones. Also a MBL PCR-RFLP was established. Upon electrophoresis of the digested products in 3% agarose gel, there were 3 patterns: in which 2 bands correspond to molecule weight 232 bp and 93 bp; 1 band, corresponds to molecule weight 325 bp and 3 bands correspond to molecule weight 325 bp, 232 bp and 93 bp, respectively. Three bands of 325 bp, 232 bp and 93 bp of point mutations were found at codon 54 of MBL coding gene. Frequencies in healthy Han and Mongolian population were 0.2321 and 0.1757 respectively. The average plasma MBL concentration was 1998.750 μg/L, with SD of 1505.152 in 56 healthy Han population and 2525.676 μg/L, with SD of 1955.188 in 37 Mongolian. A negative correlation between MBL concentration and gene mutation frequency was found in healthy Han population. Frequency of point mutation was 1.00 when the MBL concentrations were below 100 μg/L; frequency of point mutation was 0.4524 when the concentration was 100 μg/L to 1000 μg/L; and the frequency of point mutation was 0.0156 when the concentration was over 1000 μg/L. Analysis of association between MBL concentration and gene frequency in healthy Mongolian population showed that frequency of point mutation was 1.00 when the MBL concentrations were below 100 μg/L and the frequency of point mutation was 0.4583 when the MBL concentrations were 100 μg/L to 1000 μg/L; no point mutation was found when the concentration was over 1000 μg/L. It is concluded that the frequencies of mutation at codon 54 of MBL coding gene had been determined in both healthy Hans and Mongolian population, and the frequency was higher in healthy Hans than that of Mongolian, but no statistical significance (χ 2=0.8574, P >0.05). The MBL level was lower in healthy Hans than in Mongolian population, but there was no statistical significance( t =1.448, 0.1< P <0.2). There was a negative correlation between frequency of point mutation and MBL concentrations in both Hans and Mongolian population( r =-0.62, r =-0.641).展开更多
基金Projects(2006BA104B04-1,2006BAE04B07-3)supported by the National Science and Technology supporting Program of ChinaProject(2007KZ05)supported by the Science and Technology Foundation of Changchun City,China+1 种基金Project supported by"985 Project"of Jilin University,ChinaProject supported by the Open Subject of State Key Laboratory of Rare Earth Resource Utilization(2008)
文摘The effects of semi-solid isothermal process parameters on the microstructure evolution of Mg-Gd rare earth alloy produced by strain-induced melt activation(SIMA)were investigated.The formation mechanism of the particles in the process of the isothermal treatment was also discussed.The results show that the microstructure of the as-cast alloy consists ofα-Mg solid solution, Mg5RE and Mg24RE5(Gd,Y,Nd)phase.After being extruded with an extrusion ratio of 14:1 at 380℃,the microstructure of Mg-Gd alloy changes from developed dendrites to near-equiaxed grains.The liquid volume fraction of the semisolid slurry gradually increases with elevating isothermal temperature or prolonging isothermal time during the partial remelting.To obtain an ideal semisolid slurry,the optimal process parameters for the Mg-Gd alloy should be 630℃for isothermal temperature and 30 min for the corresponding time,respectively,where the volume fraction of the liquid phase is 52%.
基金Projects(50804023,50474007) supported by the National Natural Science Foundation of ChinaProject(GJJ08006) supported by the Jiangxi Provincial Education Department,China
文摘It is economically advantageous to cast wrought aluminum alloys directly into near-net-shape components.The objective of the present work is to take advantage of the rheoforming with 7075 alloy to improve the competitiveness of this emerging technology in the manufacture of wrought aluminum alloy.High quality semi-solid slurry was produced,in which primary α(Al) presents in diameter of 62 μm and shape factor of 0.78 and features no eutectics entrapped.Higher forming pressure results in small grain size,improved shape factor and higher density.Especially,rheoforming can effectively reduce the occurrence of hot tearing.The average yield strength and elongation of the rheoformed samples in the T6 condition are 483 MPa and 8%,respectively.
基金Project(200831800044) supported by the Ministry of Communication of ChinaProject(50878054) supported by the National Natural Science Foundation of ChinaProject(06Y31) supported by the Department of Communication of Zhejiang Province,China
文摘A new testing procedure to estimate the low-temperature stiffness of the reclaimed asphalt pavement （RAP） binder was developed. In the testing procedure, the SuperpaveTM Bending Beam Rheometer （BBR） with special modifications and binder blending charts by Asphalt Institute were utilized. Modifications involved the development of a new kind of sample mold and different testing parameters were made to BBR testing procedure to capture the theological properties of bitumen mortars produced by mixing fresh binder with fine RAP materials or RAP aggregate. The stiffness relationship between binder and bitumen mortar was established based on the BBR test results. The blended binder stiffness in bitumen RAP mortar was estimated from the RAP mortar stiffness based on the binder-mortar relationship. And finally, the RAP binder stiffness was estimated from the blended binder and fresh binder stiffness based on the blending charts by Asphalt Institute. The results indicate that the new procedure can capture the rheological properties of bitumen mortar and can be used to estimate the low temperature stiffness of RAP binder without binder extraction and/or any chemical treatments.
基金funded by the Thai Research Fund (Contract No.MRG5280215)the Royal Golden Jubilee Ph.D. Program (Grant No.PHD/0134/2551)
文摘Semi-solid metal processing is being developed in die casting applications to give several cost benefits. To efficiently apply this emerging technology, it is important to understand the evolution of microstructure in semi-solid slurries for the control of the theological behavior in semi-solid state. An experimental apparatus was developed which can capture the grain structure at different times at early stages to understand how the semi-solid structure evolves. In this technique, semi-solid slurry was produced by injecting fine gas bubbles into the melt through a graphite diffuser during solidification. Then, a copper quenching mold was used to draw some semi-solid slurry into a thin channel. The semi-solid slurry was then rapidly frozen in the channel giving the microstructure of the slurry at the desired time. Samples of semi-solid 356 aluminum alloy were taken at different gas injection times of 1, 5, 10, 15, 20, 30, 35, 40, and 45 s. Analysis of the microstructure suggests that the fragmentation by remelting mechanism should be responsible for the formation of globular structure in this rheocasting process.
文摘The aim of this study was to analyze the point mutation of the exon 1 at codon 54 of the mannose (or mannan)-binding lectin (MBL) gene in healthy individuals of Chinese Hans and Mongolian population, and to find out any association between the plasma levels of MBL and the gene mutation frequency in both groups of individuals. Blood samples were collected randomly from 56 healthy individuals of Chinese Hans and 37 Mongolian. The detection of the point mutations of the MBL gene was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and detections for plasma levels of MBL were determined by using MBL ELISA kits. A MBL PCR method of assay was established with high specificity, and good reproducibility. By optimizing the PCR condition, the optimal annealing temperature was 55℃, and the lowest detection limit was 160 pg. No bands were found in non-specificity samples (HAV, HBV, HCV and TB), and the sequences of PCR products were the same as the expected ones. Also a MBL PCR-RFLP was established. Upon electrophoresis of the digested products in 3% agarose gel, there were 3 patterns: in which 2 bands correspond to molecule weight 232 bp and 93 bp; 1 band, corresponds to molecule weight 325 bp and 3 bands correspond to molecule weight 325 bp, 232 bp and 93 bp, respectively. Three bands of 325 bp, 232 bp and 93 bp of point mutations were found at codon 54 of MBL coding gene. Frequencies in healthy Han and Mongolian population were 0.2321 and 0.1757 respectively. The average plasma MBL concentration was 1998.750 μg/L, with SD of 1505.152 in 56 healthy Han population and 2525.676 μg/L, with SD of 1955.188 in 37 Mongolian. A negative correlation between MBL concentration and gene mutation frequency was found in healthy Han population. Frequency of point mutation was 1.00 when the MBL concentrations were below 100 μg/L; frequency of point mutation was 0.4524 when the concentration was 100 μg/L to 1000 μg/L; and the frequency of point mutation was 0.0156 when the concentration was over 1000 μg/L. Analysis of association between MBL concentration and gene frequency in healthy Mongolian population showed that frequency of point mutation was 1.00 when the MBL concentrations were below 100 μg/L and the frequency of point mutation was 0.4583 when the MBL concentrations were 100 μg/L to 1000 μg/L; no point mutation was found when the concentration was over 1000 μg/L. It is concluded that the frequencies of mutation at codon 54 of MBL coding gene had been determined in both healthy Hans and Mongolian population, and the frequency was higher in healthy Hans than that of Mongolian, but no statistical significance (χ 2=0.8574, P >0.05). The MBL level was lower in healthy Hans than in Mongolian population, but there was no statistical significance( t =1.448, 0.1< P <0.2). There was a negative correlation between frequency of point mutation and MBL concentrations in both Hans and Mongolian population( r =-0.62, r =-0.641).
