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The phase diagrams and thermodynamic properties in the Ag–Er and Er–Y binary systems have been assessed by using the CALPHAD (Calculation of Phase Diagrams) method on the basis of the experimental data including the thermodynamic properties and phase equilibria. The Gibbs free energies of the liquid, bcc, fcc, and hcp phases were described by the subregular solution model with the Redlich–Kister equation, and those of intermetallic compounds (Ag2Er and AgEr phases) were treated as stoichiometric compounds, and Ag51Er14 phase was modeled by the sublattice model in the Ag–Er binary system. The thermodynamic parameters of the Ag–Er and Er–Y binary systems were obtained, and an agreement between the calculated results and experimental data was obtained for each binary system.

通讯作者地址: Wang, CP (通讯作者), Xiamen Univ, Dept Mat Sci & Engn, Coll Mat, Xiamen 361005, Peoples R China 地址: 1. Xiamen Univ, Dept Mat Sci & Engn, Coll Mat, Xiamen 361005, Peoples R China 2. Xiamen Univ, Res Ctr Mat Design & Applicat, Xiamen 361005, Peoples R China 3. Chongqing Univ, Coll Mat Sci & Engn, Chongqing 400045, Peoples R China 电子邮件地址: wangcp@xmu.edu.cn

通讯作者地址: Liu, XJ (通讯作者), Xiamen Univ, Dept Mat Sci & Engn, Coll Mat, Xiamen 361005, Peoples R China 地址: 1. Xiamen Univ, Dept Mat Sci & Engn, Coll Mat, Xiamen 361005, Peoples R China 2. Xiamen Univ, Res Ctr Mat Design & Applicat, Xiamen 361005, Peoples R China 3. Chongqing Univ, Coll Mat Sci & Engn, Chongqing 400045, Peoples R China 电子邮件地址: lxj@xmu.edu.cn

The phase diagrams and thermodynamic properties in the Ag–Tb and Ag–Ho binary systems have been assessed by using the CALPHAD (Calculation of Phase Diagrams) method on the basis of the experimental data including the thermodynamic properties and phase equilibria. The Gibbs free energies of the liquid, bcc, fcc and hcp phases were described by the substitution solution model with excess energy expressed by Redlich–Kister polynomial, and those of intermetallic compounds (Ag2Tb, AgTb, Ag2Ho and AgHo phases) were treated as stoichiometric compounds, and Ag51 Tb14 and Ag51 Ho14 phases were modeled by the sublattice model in these two binary systems. The thermodynamic parameters of each phase in the Ag–Tb and Ag–Ho binary systems were obtained, and an agreement between the calculated results and experimental data was obtained in each binary system.

The Cu-B system was investigated via a hybrid approach of key experiment and thermodynamic modeling. Based on the critically assessed Cu-B phase diagram, seven crucial alloys were selected and prepared by arc melting the pure elements. An inductively coupled plasma-atomic emission spectrometric analysis was conducted to determine the compositions of the prepared alloys. The phase equilibria were determined by using x-ray diffraction, electron probe microanalysis, and differential thermal analysis. The temperature associated with the eutectic reaction, $$ {\text{L}}\Leftrightarrow {\text{(B)}} + {\text{(Cu)}},$$ was measured to be 1028 ± 2 °C. First-principles calculations indicate that the energy of inserting a B atom into the interstitial vacancy (Va) site of the lattice for Cu atoms is marginally lower than that of substituting for a Cu atom with a B atom. Consequently, the sublattice model (Cu)(B, Va) in which B atoms occupy the interstitial sites was employed for the fcc (Cu) phase rather than the model (Cu, B)(Va) in which B atoms substitute for Cu atoms. A thermodynamic modeling of the Cu-B system was then performed by considering the reliable literature data and the present experimental results. A good agreement between modeling and experiment was obtained.

National Natural Science Foundation of China [50425101, 50771087, 50771088, 50725413]; Ministry of Education, PR China [707037]; National Basic Research Program of China [2007CB613704]; Japan Science and Technology Agency (JST)

An improved neural network model was developed for prediction of mechanical properties in the design and development of new types of magnesium alloys by refining the types of input variables and using a more reasonable algorithm. The results showed that the improved model apparently decreased the prediction errors, and raised the accuracy of the prediction results. Better preprocessing parameters were found to be [0.15, 0.90] for the tensile strength, [0.1, 0.9] for the yield strength, and [0.15, 0.90] for the elongation. When the above parameters were used, the relativity for predicition of strength was bigger than 0.95. By using improved ANN analysis, more reasonable process parameters and composition could be obtained in some magnesium alloys without addition of strontoum.

The effects of various Mg-Sr master alloys (conventional as-cast, rapidly-solidified, rolled and solutionized) on microstructural refinement of ZK60 magnesium alloy were investigated. The results indicate that the refinement efficiency of various Mg-Sr master alloys in ZK60 alloy is different. The rolled Mg-Sr master alloy is found to have relatively higher refinement efficiency than the conventional as-cast, solutionized and rapidly-solidified Mg-Sr master alloys. After being treated with the rolled Mg-Sr master alloy, the ZK60 alloy obtains the minimum average grain size of 33 μm. The difference of various Mg-Sr master alloys in refinement efficiency might be related to the initial microstructure change of various Mg-Sr master alloys.

The effects of yttrium addition on microstructure and mechanical properties of as-extruded AZ31 magnesium alloys were investigated by OM, XRD and SEM. The results show that the addition of yttrium results in the formation of a new phase, Al2Y. When the addition of yttrium is higher than 1.48%-2.91% (mass fraction), another new phase, Al3Y5Mn7, forms, and the amount of β-Mg17Al12 phase in the AZ31 alloy decreases sharply. The tensile test at room temperature indicates that the yield strength of as-extruded AZ31 alloys improves with the addition of yttrium, but the elongation decreases, which is possibly related to the formation of coarse blocky compounds containing yttrium and the grain coarsening in the alloys.

Mg-Cu-Y-Zn bulk metallic glasses (BMG) and in situ bulk metallic glass matrix composites were prepared by copper mold casting under the low vacuum with the argon atmosphere, and the raw materials used in preparing the Mg-Cu-Y-Zn alloys were commercially pure materials. The microstructures of the bulk samples were analyzed by X-ray diffractometer (XRD) and the thermal stability of samples was investigated by using a differential scanning calorimeter (DSC). The thermal stability of sample prepared with commercially pure raw materials is close to that of sample prepared with the high pure raw materials for the BMG Mg 65+ X (Cu 0.66 Y 0.33 ) 30– X Zn 5 ( X =6). With the increase of Mg content, Mg-Cu-Y-Zn composites are prepared, in which Mg solid solution flakes and Y 2 O 3 flakes are dispersed. In comparison with monolithic Mg-based BMG alloys, the composites exhibit significant improvement in mechanical properties, e.g. a compressive plastic strain about 7% and an ultimate strength of 1 170 MPa in Mg 65+ X (Cu 0.66 Y 0.33 ) 30– X Zn 5 ( X =14). It is suggested that the enhancement of the mechanical properties of the composites can be attributed to the generation of multiple shear bands and the quantity of the Mg solid solution flakes.

In the paper, the effects of solutionized Al–10Sr master alloys on grain refinement of AZ31 magnesium alloy are investigated. The results indicate that the effects of solid solution treatment on the morphology and size of Al 4 Sr phases in the commercial Al–10Sr master alloy are obvious. With the solutionized temperature increasing from 400 °C to 600 °C, the size of Al 4 Sr phases reduces gradually, and the morphology of Al 4 Sr phases evolves from coarse block shape to fine block and flake shapes. Comparing with the commercial Al–10Sr master alloy, the solutionized Al–10Sr master alloys exhibit higher refinement efficiency to AZ31 magnesium alloy, and the refinement efficiency increases with the solutionized temperature increasing from 400 °C to 600 °C. The mechanism might be related to the dissolution rates of Al 4 Sr phases in the melt of AZ31 magnesium alloy.

National Natural Science Foundation of China [50425101, 50771087, 50771088, 50725413]; Ministry of Education, PR China [20050384003, 707037]; National Basic Research Program of China [2007CB613704]; Japan Science and Technology Agency (JST)

The effects of Al-10Sr master alloys on grain refinement of AZ31 magnesium alloy were investigated, and the refinement efficiency of different Al-10Sr master alloys (commercial, solubilized, rolled and remelted+rapidly cooled) was compared and analyzed. The results indicate that the morphology and size of Al 4 Sr phases in the microstructures of different Al-10Sr master alloys, are of great difference. For the commercial Al-10Sr master alloy, the Al 4 Sr phases evolve from coarse block shape to relatively fine block shape after being dissolved at 500 °C for 4 h and followed by water quenching; but after being rolled at 300 °C for 50% reduction or remelted and followed by rapid cooling, the Al 4 Sr phases mainly exhibit fine granule and fibre shapes. In addition, the different Al-10Sr master alloys can effectively reduce the grain size of AZ31 magnesium alloy, but their refinement efficiency is different. The refinement efficiency of the Al-10Sr master alloy obtained by remelting and rapid cooling is the best, then the rolled, solubilized and commercial Al-10Sr master alloys are in turn. The difference of refinement efficiency for different Al-10Sr master alloys may be related to the dissolution rates of Al 4 Sr phases with different morphologies and sizes in the melt of AZ31 magnesium alloy.

The mechanical properties and processing performances of conventional magnesium alloys still could not meet the need of important application fields due to some demerits, such as poor formability, low creep resistance and unsatisfactory strength at elevated temperature. Recent investigations have shown that additions of strontium to magnesium alloys are effective in improving creep resistance of the alloys at temperatures above 150°C, and some new types of magnesium alloys containing strontium have been developed. The mechanical properties and microstructure of magnesium-aluminum based alloys containing strontium are reviewed, and the considerable discrepancy among the research results is discussed. Special attentions are paid to the mechanical properties, compounds and grain refinement of Mg-Al-Sr based alloys. The Sr/Al ratio is thought to be important to control the microstructure of Mg-Al-Sr alloys. The mechanism of grain refinement caused by strontium addition in magnesium alloys remains unclear.

In the article, the effects of Al–10Sr and Mg–10Sr master alloys on the grain refinement of AZ31 magnesium alloy, are compared and analyzed. The results indicate that adding Al–10Sr or Mg–10Sr master alloys to AZ31 magnesium alloy could effectively reduce its grain size, but the refinement efficiency of Mg–10Sr master alloys is higher than that of the Al–10Sr master alloys. In addition, for a given melt holding time, the refinement efficiency of the two master alloys respectively increase with Sr adding amount increasing from 0 to 0.1 wt%, and the increasing laws are similar. For a given Sr adding amount, the refinement efficiency of Al–10Sr mater alloy gradually increases with the melt holding time increasing from 20 to 80 min, but its changing is not obvious for the Mg–10Sr mater alloy. The difference of refinement efficiency for the Al–10Sr and Mg–10Sr master alloys might be related to the dissolution modes and rates of Al4Sr and Mg17Sr2 phases in the melt of AZ31 magnesium alloy.

The harmful effect of silicon in high purity aluminium foils for capacitors could be decreased by additional heat treatment and additional deformation as well as two stage final annealing. It was found that the cube texture fraction in the high purity aluminium foils with higher silicon impurity was increased obviously by additional annealing and rolling. The cube texture of >95 vol.-% could be achieved when the additional rolling deformation of 20–40% was carried out. It was found that the annealing temperature of 200–250°C, not only for additional annealing but also for two stage final annealing, was reasonable for obtaining higher cube texture fraction. The experimental results also showed that the change of hot band annealing temperature had little influence on the cube texture fraction in high purity aluminium foils when additional annealing was carried out at ∼220°C.

The effects of silicon additions up to 3.5 wt pct on the as-cast carbides, as-quenched carbides, and as-tempered carbides of high-speed steels W3Mo2Cr4V, W6Mo5Cr4V2, and W9Mo3Cr4V were investigated. In order to further understand these effects, a Fe-16Mo-0.9C alloy was also studied. The results show that a critical content of silicon exists for the effects of silicon on the types and amount of eutectic carbides in the high-speed steels, which is about 3, 2, and 1 wt pct for W3Mo2Cr4V, W6Mo5Cr4V2, and W9Mo3Cr4V, respectively. When the silicon content exceeds the critical value, the M2C eutectic carbide almost disappears in the tested high-speed steels. Silicon additions were found to raise the precipitate temperature of primary MC carbide in the melt of high-speed steels that contained d-ferrite, and hence increased the size of primary MC carbide. The precipitate temperature of primary MC carbide in the high-speed steels without d-ferrite, however, was almost not affected by the addition of silicon. It is found that silicon additions increase the amount of undis-solved M6C carbide very obviously. The higher the tungsten content in the high-speed steels, the more apparent is the effect of silicon additions on the undissolved M6C carbides. The amount of MC and M2C temper precipitates is decreased in the W6Mo5Cr4V and W9Mo3Cr4V steels by the addition of silicon, but in the W3Mo2Cr4V steel, it rises to about 2.3 wt pct.

In this study, biodegradable Mg-Sn alloys were fabricated by sub-rapid solidification, and their microstructure, corrosion behavior and cytotoxicity were investigated by using optical microscopy, scanning electron microscopy equipped with an energy dispersive X-ray spectroscopy, X-ray diffraction, immersion test, potentiodynamic polarization test and cytotoxicity test. The results showed that the microstructure of Mg-1Sn alloy was almost equiaxed grain, while the Mg-Sn alloys with higher Sn content (Sn≥3 wt.%) displayed α-Mg dendrites, and the secondary dendrite arm spacing of the primary α-Mg decreased significantly with increasing Sn content. The Mg-Sn alloys consisted of primary α-Mg matrix, Sn-rich segregation and Mg2Sn phase, and the amount of Mg2Sn phases increased with increasing Sn content. Potentiodynamic polarization and immersion tests revealed that the corrosion rates of Mg-Sn alloys increased with increasing Sn content. Cytotoxicity test showed that Mg-1Sn and Mg-3Sn alloys were harmless to MG63 cells. These results of the present study indicated that Mg-1Sn and Mg-3Sn alloys were promising to be used as biodegradable implants.

Magnetorheological (MR) transmission transmits the torque by the shear stress of the MR fluids. In this paper, the operational Model of MR fluids transmission is investigated theoretically. Bingham model is used to describe the properties of the MR fields. Based on the direct shear operational mode, the transmission modes of the MR fluid between two parallel plates, two circular plates and two circular plates are analyzed respectively. The expressions of the force and the torque developed by the shear stress of MR fluids in these transmission modes are derived. The research results show that the MR fluids can be used in transmission. The torque increases as the applied magnetic field strength increase.

The microstructures and mechanical properties of Mg–2.0Zn–1.0Mn (ZM21) alloys with certain amount of Ce and Nd additions were investigated, and the influence mechanism of Ce and Nd on the microstructures and mechanical properties of extruded alloys was discussed. The results indicated that the addition of Nd and Ce can refine the grains in ZM21 alloy, for which the distribution density of second phase particle played a major role to hinder the growth of dynamic recrystallization (DRX) grain in alloys by adding a content of 0.4 wt.% Ce and Nd. The average grain size of ZM21 alloy with the additions of 0.4 wt.% Nd and Ce reached 6 ± 3 μm and 13 ± 2 μm, respectively. Adding Ce and Nd to ZM21 alloy, the changes of mechanical properties were mainly attributed to a reduction in basal texture intensity, refinement grain size as well as the dispersion density and distribution position of fine second phase particles. Furthermore, by addition of Ce and Nd to ZM21 alloy, the non-basal plane slip system could be activated which decreased the basal texture intensity.

The influence of alloying elements on the stacking fault energy (SFE) of Mg–Y–Zn–Zr alloys was calculated by using first-principles, and the microstructure of as-cast Mg-1.05Y-0.79Zn-0.07Zr (mole fraction, %) alloy prepared by conventional casting was investigated by SEM, TEM and HRTEM. The block-like long period stacking ordered (LPSO) phase, the lamellar LPSO phase and stacking faults were observed simultaneously and the lamellar LPSO structure and stacking faults were both formed on (0001)α-Mg habit plane and grown or extended along [01i0]α-Mg direction. The calculation results by the first-principles showed that the addition of Y can sharply decrease the stacking fault energy of the Mg–Zn–Y–Zr alloy, while Zn slightly increases the stacking fault energy of the alloy. The influence of stacking fault energy on the formation of LPSO was discussed. It shows that LPSO may nucleate directly through stacking faults and the lower stacking fault energy was in favor of formation of LPSO.