Showing papers in "Materials Transactions in 2003"
TL;DR: In this paper, a tensile testing of AZ31 Mg alloys was conducted at temperatures ranging from room temperature to 523K, and the occurrence of grain-boundary sliding (GBS) at room temperature was demonstrated by the displacement of scribed lines across grain boundaries of deformed samples.
Abstract: Rolled sheets of AZ31 Mg alloys were subjected to tensile testing at temperatures ranging from room temperature to 523K The occurrence of grain-boundary sliding (GBS) at room temperature was demonstrated by the displacement of scribed lines across grain boundaries of deformed samples Surface relief of deformed samples was measured by use of a scanning laser microscope GBS strain was calculated from the measured surface step height, and its temperature dependence was analyzed by a Dorn-type constitutive equation GBS above 423K was found to be pure GBS that was activated by resolved applied shear stress acting on grain boundaries The activation energy for GBS was found to be 80 kJ/mol, which is in agreement with the activation energy for grain boundary diffusion Meanwhile, GBS below 373K was found to be slipinduced GBS, and its extent was found to be significantly greater than that expected from extrapolation of high-temperature values The slipinduced GBS is considered to occur by plastic compatibility conditions in the presence of plastic strain anisotropy and by absorption and dissociation of lattice dislocations at grain boundaries
275 citations
TL;DR: In this article, the evolution of a magnesium alloy AZ31 was studied in compression at 673 K (0.73T m ) by optical and SEM/OIM microscopy, and it was concluded that new grain evolution in this alloy is controlled by a deformation-induced continuous reaction.
Abstract: Dynamic grain evolution of a magnesium alloy AZ31 was studied in compression at 673 K (0.73T m ) by optical and SEM/OIM microscopy. The flow curve shows rapid hardening accompanied by a stress peak at a relatively low strain (e p = 0.12), followed by strain softening and then a steady state flow stress at high strains. Fine grains evolved at corrugated grain boundaries at around E P and developed rapidly fluting strain softening, finally leading to a full structure of equiaxed fine grains. Such characteristics of new grain evolution and flow behavior are apparently similar to those in conventional, i. e. discontinuous, dynamic recrystallization (DRX). On the other hand. kink bands were observed frequently near corrugated grain boundaries and also in grain interiors, even around e p . The misorientation of the boundaries of the kink bands increases rapidly during strain softening and approaches a saturation value of around 43°. at high strains. The average size of the regions fragmented by kink bands is almost the same as that of the new grains. It is concluded, therefore, that new grain evolution in this alloy is controlled by a deformation-induced continuous reaction, i.e. continuous DRX.
183 citations
TL;DR: In this article, the microstructure of a Ti-Nb alloy that contains 14 to 26 mass% Nb consists ofandphases, with phase being the dominant one.
Abstract: This study attempts to develop Ti-Nb alloys with elastic moduli that approach that of human bone. The experimental results reveal that the microstructure of a Ti-Nb alloy that contains 14 mass% Nb consists ofandphases, withphase being the dominant one. The proportion of thephase decreases gradually as the Nb content increases, and the microstructure becomes completely thephase when the Nb content exceeds 34 mass%. Moreover, the ! phase can be detected using XRD and TEM in alloys with a Nb content from 30 to 34 mass%. Over the Nb range studied (14 to 40 mass%), the elastic modulus decreases from 14 to 26 mass% Nb, and then increases to a maximum at 34 mass% Nb, before falling again as Nb content is increased further. The elastic modulus of the Ti-Nb alloys is closely related to the microstructure (or Nb content) of the alloys. The fall in the elastic modulus with the increasing Nb content from 14 to 26 mass% is associated with a gradual decrease in the proportion of thephase in the microstructure, while the precipitation of the ! phase accounts for the increase in the elastic modulus over the intermediate range of Nb (30 to 34 mass%). The tensile strength of Ti-Nb alloys increases slightly from 14 to 26 mass% Nb, and then increases markedly with a Nb content of up to 34 mass%, before falling drastically as Nb content is increased further. A similar pattern was obtained for 0.2% proof stress, while the elongation vs. %Nb curve was just the reverse of the T.S. vs. %Nb curve, as expected. A Ti-Nb alloy with a relatively high Nb content (above 36 mass%) is preferred to other compositions for use in medical implants with a reduced stress shielding effect.
174 citations
TL;DR: In this paper, the formation of nanocrystalline structure (NS) in steels by various severe plastic deformation processes, such as ball milling, a ball drop test, particle impact deformation and air blast shot peening are demonstrated.
Abstract: The formation of nanocrystalline structure (NS) in steels by various severe plastic deformation processes, such as ball milling, a ball drop test, particle impact deformation and air blast shot peening are demonstrated. Layered or equiaxed nanograined region appeared near the specimen surface and dislocated cell structured region appeared interior of specimens. These regions are separated with clearly defined boundaries. The deformation induced nanograined regions have the following common specific characteristics: 1) with grains smaller than 100 nm and low dislocation density interior of grains, 2) extremely high hardness, 3) dissolution of cementite when it exist and 4) no recrystallization and slow grain growth by annealing. The deformation conditions to produce NS was discussed based on the available data in literatures. It was suggested that the most important condition is to impose a strain larger than about 7. High strain rates, low deformation temperature, multidirectional deformation, hydrostatic pressure are considered to be favorable conditions to produce NS. Introducing alloying elements, precipitates and second phase also enhance nanocrystallization by suppressing recovery. The mechanisms of the formation of sharply defined boundaries which separate nanograined structure region from dislocated cell structured region were discussed with respect to impurities, martensitic transformation and deformation. It was suggested several mechanisms may operate simultaneously in the formation of the clear boundaries.
165 citations
TL;DR: In this paper, the formation of nanocrystalline structure (NS) on the surface of bulk steel samples by a particle impact and air blast shot peening techniques was studied.
Abstract: The formation of nanocrystalline structure (NS) on the surface of bulk steel samples by a particle impact and air blast shot peening techniques was studied. Nanocrystalline layers with several microns thick were successfully fabricated by these methods. The nanocrystalline layers produced in the present study have extremely high hardness and separated from adjacent deformed morphology region with sharp boundaries. By annealing, nanocrystalline layers showed slow grain growth without recrystallization. Those characteristics are similar to those observed in the NS produced by ball milling and a ball drop deformation. It was suggested that to produce NS by deformation a large strain is a necessary condition and a high strain rate and low temperature are favorable conditions.
142 citations
TL;DR: In this article, the relationship between tensile properties and microstructural parameters that include grain size and the texture generated by ECAE processing was investigated at room temperature, and it was shown that crystallographic orientation has a profound effect on the tensile property of AZ31 alloy, and grain size has little effect.
Abstract: Mg–3%Al–1%Zn (AZ31) alloy was subjected to ECAE (Equal Channel Angular Extrusion) processing under various processing conditions. Then tensile tests were carried out at room temperature to investigate the relationship between tensile properties and microstructural parameters that include grain size and the texture generated by ECAE processing. In 4-pass ECAE specimens processed at 523 K, tensile ductility is improved as a result of easy basal slip during tensile test along the extrusion direction, because such specimens have textures in which the basal plane is inclined at 45 � to the extrusion direction. On the other hand, in the specimens processed at 573 K, 0.2% proof stress is higher than those of specimens processed at lower temperatures, but elongation is smaller. This is because of difficult basal slip caused by the textures in which the basal plane is oriented parallel to the extrusion direction. However, 8-pass specimens processed at 473 K and subsequently annealed, which have similar textures but different grain sizes (d), exhibit clear grain size dependencies of 0.2% proof stress (� 0:2) according to Hall-Petch relationship; � 0:2 ¼ 30 þ 0:17d � 1=2 . Therefore, crystallographic orientation has a profound effect on the tensile properties of AZ31 alloy, and grain size has a little effect.
126 citations
TL;DR: In this paper, the effect of phase transformation, the diffusion anisotropy, the atomic size effect and the correlation between solubility and diffusivity is discussed on the basis of several features.
Abstract: Impurity diffusion in -Ti and -Zr is characterized by fast interstitial diffusion of small atoms and slow substitutional diffusion of large atoms. The mechanism of the fast diffusion is discussed on the basis of the several features: the effect of phase transformation, the diffusion anisotropy, the atomic size effect and the correlation between solubility and diffusivity. The temperature dependence of the diffusion coefficients of all the solutes and solvent Ti studied in -Ti follows the Arrhenius law, whereas in -Zr, all the elements studied with exception of Ti show downward curvatures that follow the self-diffusion behaviour in -Zr. The influence of ultra-fast diffusion impurities on the diffusion process in these matrices, as well as the possibility that different mechanism acts in each matrix is analyzed.
114 citations
TL;DR: In this paper, the progress in the chemical vapor deposition of iridium, platinum, rhodium and palladium metals is reviewed and representative results on CVD of these metals are presented according to the type of metal organic complexes used.
Abstract: This article reviews the progress in the chemical vapor deposition of iridium, platinum, rhodium and palladium metals. In the course of the last decade the number of articles on CVD of this group of metals has increased significantly. A wide variety of metal organic complexes have been investigated as potential precursors and appreciable results have been obtained. However, some aspects such as low deposition rates and impurity incorporation into the films still remain as concerns in this area. The representative results on CVD of these metals are presented according to the type of metal organic complexes used.
110 citations
TL;DR: In this article, the orientation of the crystal axis of the hydroxyapatite was determined by aligning it with a magnetic field in a colloidal filtration process under a high magnetic field.
Abstract: A hydroxyapatite is most suitable biomaterial for clinical application, because it is a main component which constitutes bones and teeth of an organism. Since the hydroxyapatite has different biocompatibility and absorptive activity of proteins for its crystal plane, it is necessary to use the appropriate crystal plane for use in vivo. Thus, the crystal orientation of the hydroxyapatite is one of the very crucial subjects in biomaterials processing. In this study, the control of crystal orientation of the hydroxyapatite has been conducted in the colloidal filtration (slip casting) process under a high magnetic field and a new process where the high magnetic field is introduced in the heat substrate method developed by Okido et al. The usefulness of the processes has been confirmed through the orientation index evaluated by X-ray diffraction patterns and scanning electron microscope (SEM) images of hydroxyapatite crystals. The crystal axis of hydroxyapatite aligned by a magnetic field was determined.
108 citations
TL;DR: In this article, the authors studied the structural properties of AZ31-O magnesium alloys with different layers of the plates in different planar directions and found that the properties of the basal planes of the hexagonal lattice become aligned parallel to the sheet plane.
Abstract: On the AZ31-O magnesium alloy plates of 20 mm in thickness, basal plane texture was studied for the samples taken from different layers. Compression tests were carried out in the rolling, width and thickness directions at room temperature. Tensile tests were conducted for the specimens taken from the different layers of the plates in different planar directions. The formability in deep drawing and stretch forming was evaluated for the thin sheet specimens taken from different layers of the plates and the results were discussed in relation to the texture and mechanical properties. The severity of the basal plane texture is higher at the surface layer than the inner layers. In tensile tests at room temperature, proof stress is higher for the surface layer than the inner layers, whereas elongation is lower and r-value is higher at the surface layer. In compression tests at room temperature, yield stress in the rolling and width directions is appreciably lower than in the thickness direction. At 573 K, anisotropic and non-uniform deformation behavior disappeared. Thin sheet specimens taken from inner layers of the plates showed higher formability than those from the surface layer in deepdrawing and stretch forming. It is concluded that the formability of magnesium alloy sheets can be improved by decreasing the severity of the basal plane texture. In rolling of magnesium and its alloys, the basal plane of the hexagonal lattice becomes aligned parallel to the sheet plane so that a strong basal plane texture is formed. Such textures are maintained even after recrystallization by annealing. Thus, rolled sheets of magnesium and its alloys generally show a strong anisotropy in plastic deformation behavior at around room temperature. Deformation accom- panying with thickness reduction is always difficult, that is, they show low limits of plastic deformation in cold rolling and in sheet metal forming. This is the main reason why the rolled sheets of magnesium and its alloys are not widely used in practice in spite of the recent high demands for the light- weight materials. However, high plastic anisotropy of magnesium alloy sheets becomes disappeared at tempera- tures above 473 K due to contribution of non-basal plane slip systems. At these temperatures, sheet rolling of magnesium alloys becomes much easier and the formability in deep drawing, 1-3) stretch forming, 4) bending 5) and forming limit curves 6) is appreciably improved. In thick plates of magnesium alloys, basal plane texture is considered to be less developed than in thin sheets due to lower reduction and higher rolling temperature. Additionally, mechanical properties in the thickness direction can be evaluated in thick plates. The anisotropy and non-uniformity of the basal plane texture and mechanical properties can also be discussed by testing specimens from the different layers of the plates. Obtained results are considered to suggest the desirable textures and mechanical properties for higher formability at room temperature. It has been reported in plane strain compression tests of AZ31 magnesium alloy plates that the compressive yield stress in the rolling direction is appreciably lower than in the other directions, which can be attributed to the highly developed basal plane textures. 7) However, very little has been known on the plastic behavior of magnesium plates. It is the purpose of this work to elucidate the anisotropy and non-uniformity of plastic behavior of the magnesium plates. In this work, the basal plane texture was studied for the samples taken from different layers of AZ31-O magnesium alloy plates of 20 mm in thickness. Compression tests were done in the rolling, width and thickness directions at room temperature. Tensile tests were conducted for the specimens taken from the different layers of the plates in different planar directions. Finally, formability in deepdrawing and stretch forming was evaluated for the thin sheet specimens taken from different layers of the plates and the results were discussed in relation to the texture and mechanical properties.
107 citations
TL;DR: An environmentally sound process for the extraction of neodymium (Nd) from magnet scrap was devised and its feasibility was demonstrated as mentioned in this paper, and the developed Nd extraction apparatus circulates the magnesium (Mg) as an extraction medium by maintaining a temperature difference within the reaction vessel, thus achieving continuous extraction of metal Nd from scrap, re-extraction of Mg from a Mg-Nd alloy, and finally, pure Nd metal with 97.7% purity was directly recovered without oxidation.
Abstract: An environmentally sound process for the extraction of neodymium (Nd) from magnet scrap was devised and its feasibility was demonstrated. The developed Nd extraction apparatus circulates the magnesium (Mg) as an extraction medium by maintaining a temperature difference within the reaction vessel, thus achieving continuous extraction of metal Nd from scrap, re-extraction of Mg from a Mg–Nd alloy, and finally, pure Nd metal with 97.7% purity was directly recovered from magnet scrap without oxidation. The concept of ‘‘scrap combination’’ for recycling variable materials, that is demonstrated in this study, is an important technology that can be instrumental in creating a highly developed self-sustainable society.
TL;DR: In this article, the grain refinement process during surface mechanical attrition treatment (SMAT) was investigated in materials with low stacking fault energies (SFE, Inconel 600 alloy and AISI 304 stainless steel) by means of transmission electron microscopy and high-resolution electron microscope, respectively.
Abstract: Surface mechanical attrition treatment (SMAT) technique was developed to synthesize a nanostructured surface layer on metallic materials for upgrading their overall properties and performance. In this paper, the grain refinement process during SMAT was investigated in materials with low stacking fault energies (SFE, Inconel 600 alloy and AISI 304 stainless steel) by means of transmission electron microscopy and high-resolution electron microscopy, respectively. Grain subdivision was performed by the interaction of mechanical microtwins with dislocations in Inconel 600. For AISI 304 stainless steel with a lower SFE, twin-twin intersections subdivide initial grains into refined blocks with sizes ranging from nanometers to submicrometers. Such grain subdivision processes of the interaction of microtwins with dislocations or microtwins obviously differ from those observed in the high SFE materials in which dislocation interactions predominate the grain refinement.
TL;DR: In this paper, a new long-period hexagonal structure with six and fourteen layered atomic configurations was formed in melt-spun Mg97Ln2Zn1 (Ln=Y, Gd and Sm) ternary alloys annealed at 573 K for 1.2-3.6 ks.
Abstract: Novel long-period hexagonal structures with six and fourteen layered atomic configurations were formed in melt-spun Mg97Ln2Zn1 (Ln=Y, Gd and Sm) ternary alloys annealed at 573 K for 1.2-3.6 ks and in an as-spun Mg97Y2Zn1 alloy, respectively. The Mg-based alloys containing La or Ce as the Ln element have a mixed structure of hcp Mg and compound phases and no long-period hexagonal structure is formed in the as-spun and annealed states. There is a clear formation tendency of the novel long-period structure to increase with a decrease in the precipitation tendency of the intermetallic compound, an increase in the atomic size ratio of Ln/Mg and an enhancement of the formation tendency of Mg-based reinforced solid solution. The formation of the novel long-period structure is interpreted to result from the necessity of relaxation of strains caused by the reinforced solid solution of Ln and Zn elements into the Mg phase. In addition, the enrichment of Y and Zn elements was observed at the misfit sites of the atomic array in the fourteen layered hexagonal structure of the as-spun Mg97Y2Zn1 alloy. The atomic level segregation of Y and Zn elements is also thought to be the origin for the high stability of the long-period structure. The two types of long-period hexagonal structures found in the Mg-Ln-Zn alloys are important as a new mechanism for future development of high-strength Mgbased alloy.
Abstract: The magnetic properties of the glassy Fe-(Al, Ga)-(P, C, B, Si, Ge) alloys have been compared with those of the conventional Fe-based amorphous alloys to clarify the feature of the glassy alloys as a soft magnetic material. The glassy Fe-(Al, Ga)-(P, C, B, Si, Ge) alloys exhibit lower saturation magnetization (Js) than that of the conventional Fe-(B, Si, C) amorphous alloys with the same Fe content. The glassy alloys also have larger saturation magnetostriction constant (� s) than that of the conventional Fe-based amorphous alloys with the same Js. However, the
TL;DR: In this article, a single crystalline BaTi 2 O 5 was prepared by a floating zone method and the space group was C2, and the lattice parameters were a = 1.6909nm, b = 0.3937(1)nm, c=0.9419nm and β =103.12°.
Abstract: Single crystalline BaTi 2 O 5 was prepared by a floating zone method. The single crystal was transparent having a (001) cleavage plane. The space group was C2, and the lattice parameters were a =1.6909(9)nm, b =0.3937(1)nm, c=0.9419(4)nm and β =103.12(6)°. The permittivity perpendicular to a (010) plane showed the maximum value of 20500 at 748 K. The permittivity perpendicular to (100) and (001) planes were about 140 and 70, respectively, independent of temperature.
TL;DR: In this paper, volume and grain boundary diffusion of chromium in Ni-16mass%Cr-7mass%Fe alloys containing 0.004, 0.015 and 0.07 mass% of carbon have been measured using radioactive tracer 51 Cr over the temperature range of 858-1424K by serial radio-frequency sputtermicrosectioning technique.
Abstract: Volume and grain boundary diffusion of chromium in Ni-16mass%Cr-7mass%Fe alloys containing 0.004, 0.015 and 0.07 mass% of carbon have been measured using radioactive tracer 51 Cr over the temperature range of 858-1424K by serial radio-frequency sputter-microsectioning technique. While the volume diffusion coefficients are largely unaffected by the presence of carbon, the increase in carbon content markedly reduces the mobility of chromium atoms along the grain boundaries. As a result, the difference between the activation energy for lattice and grain boundary diffusion decreases with increase in carbon content. In fact, for 0.07 at% carbon, the activation energies for volume and the grain boundary diffusion are nearly same. Among all three alloys, the difference between the volume diffusion coefficient, D v , as well as δD gb (δ = grain boundary width; D gb = grain boundary diffusion coefficient) decreases gradually in a regular manner with the rise of temperature. Grain bounadry energy is reduced by addition of carbon and enhanced by temperature. At higher temperatures, there is no difference between the grain boundary energies of the three alloys.
TL;DR: An overview on recent progress in grain boundary (GB) diffusion study is presented with emphasis on physical phenomena encountered in GB diffusion experiments such as the linear and non-linear segregation effects.
Abstract: An overview on recent progress in grain boundary (GB) diffusion study is presented with emphasis on physical phenomena encountered in GB diffusion experiments such as the linear and non-linear segregation effects. Systematic investigations on pure and alloyed poly- and bicrystals gave conclusive information on the solute segregation behavior and allowed to extract the segregation isotherm solely from GB diffusion studies. Recent progress in fundamental understanding of diffusion processes in two-scale materials with two types of short-circuit diffusion paths is discussed on the basis of GB self-diffusion experiments and Monte-Carlo simulations in powder sintered nanocrystalline material.
TL;DR: In this article, the microstructural development of friction stir welding on an AZ91D magnesium alloy and the mechanical properties of the welds were investigated using optical and scanning electron microscopes.
Abstract: This study was carried out to grow an understanding of the microstructural development of friction stir welding on an AZ91D magnesium alloy and to evaluate the mechanical properties of the welds. AZ91D plates with the thickness of 4 mm were used, and the microstructural development of the weld zone was investigated using optical and scanning electron microscopes. Square butt welded joint with good quality was
TL;DR: Porous Pd42:5Cu30Ni7:5P20 glassy alloy rods with diameters of 7 and 10 mm and a length of about 20 mm were produced by water quenching the mixture of Pd 42:5 Cu30Ni 7:5 P20 liquid and solid salt phases at a volume fraction ratio of 7 to 9, followed by leaching treatment into water to eliminate the salt phase as discussed by the authors.
Abstract: Porous Pd42:5Cu30Ni7:5P20 glassy alloy rods with diameters of 7 and 10 mm and a length of about 20 mm were produced by water quenching the mixture of Pd42:5Cu30Ni7:5P20 liquid and solid salt phases at a volume fraction ratio of 7 to 9, followed by leaching treatment into water to eliminate the salt phase. The pores had a polyhedral shape with sizes of 125 to 250 mm. The densities were 3.3 and 4.2 Mg/m 3 and their pore fractions were evaluated as 65 and 55% for the 7 mm and 10 mm rods, respectively. The thickness of the cell walls was in the range of 50 to 250 mm. No crystalline phase was observed in the outer surface region as well as in the cell wall region. The glass transition temperature and crystallization temperature of the porous alloy rods were 578 and 679 K, respectively, in agreement with those of the pore-free alloy. Final rupture was not recognized for the porous alloys subjected to the uniaxial compressive test. The porous alloy exhibited lower Young’s modulus, lower yield strength, much higher absorption energy, being significantly different from those for the pore-free glassy alloy rod. The unique mechanical characteristics combined with high absorption energy ability indicate the possibility of future uses as a new type of structural and functional materials.
TL;DR: In this article, a fully amorphous rod with diameter of 2 mm was fabricated in Ni 60 Nb 30 Ta Ta 10 alloy by an injection casting method and the compressive failure strength of the Ni 60 nb 30Ta 10 bulk amorphized alloy is 3346 MPa.
Abstract: Enhancement of thermal stability and glass forming ability in Ni 60 Nb 40-x Ta x (x = 0, 3, 5, 10, 20 at%) alloys has been investigated. The crystallization temperature increases from 660°C in binary Ni 60 Nb 40 amorphous phase to 721°C in Ni 60 Nb 20 Ta 20 amorphous phase. The fully amorphous rod with diameter of 2 mm is fabricated in Ni 60 Nb 30 Ta 10 alloy by an injection casting method. The compressive failure strength of the Ni 60 Nb 30 Ta 10 bulk amorphous alloy is 3346 MPa.
TL;DR: In this article, the dynamic grain refinement behavior upon severe plastic deformation has been systematically studied in commercial purity copper that was heavily cold rolled to large deformations at cryogenic temperatures, enabling an investigation of the various dynamic recrystallization phenomena upon further deformation.
Abstract: The dynamic grain refinement behavior upon severe plastic deformation has been systematically studied in commercial purity copper that was heavily cold rolled to large deformations at cryogenic temperatures. The low-temperature rolling allows the accumulation of extraordinarily high densities of dislocations in Cu, enabling an investigation of the various dynamic recrystallization phenomena upon further deformation. The eventual steady-state grain sizes achieved, as well as the dynamic recrystallization mechanisms, are studied using controlled deformation tests combined with transmission electron microscopy. The dominant mechanisms observed to contribute to grain refinement in Cu include the classical migration dynamic recrystallization process, the deformation twinning, as well as the continuous dynamic recrystallization via progressive lattice rotation upon deformation to extremely large strains. The strain rate and deformation temperature have strong effects on the operative mechanisms and the grain sizes achieved in the ultrafine and nanocrystalline regimes.
TL;DR: In this paper, the authors used two parallel plate electrodes made of Cu and having a given cross-section configuration to separate ABS, PS, and PP components in a two-step triboelectrostatic process.
Abstract: The objective of this study was to triboelectrostatically separate artificial plastic mixture of three kinds of components (i.e. ABS, PS and PP mixture). The mixture is charged by friction in tribo-cyclone. After a given period of time inside the tribo-cyclone, the charged plastic flakes fell down freely through a horizontal electric field into collection bins. The DC electric field of maximum 400 kV/m is created by using two parallel plate electrodes made of Cu and having a given cross-section configuration. The plastic flakes of the mixtures are drawn to either positive or negative electrode according to the polarity of the charge and are separated by falling in different bins. The purification of three-component mixture is accomplished by a two-step triboelectrostatic process. Separation tests in a batch laboratory triboelectrostatic separator showed that the efficiency of the separation is strongly depended on tribocharging time, air inlet velocity, and electric field strength. Products of ABS, PS and PP with a grade of 92.1%, 84.9% and 90.0% respectively have been achieved with recoveries above 73.0%.
TL;DR: In this paper, a single roller melt-spinning technique was used to rapidly solidify Ni-Nb-Zr alloys in a ribbon form with a thickness of about 20 mm.
Abstract: Rapidly solidified Ni–Nb–Zr alloys in a ribbon form with a thickness of about 20 mm were prepared by a single roller melt-spinning technique. Amorphous alloys were formed in the composition range of 20 to 75 at%Ni, 0 to 60 at%Nb and 0 to 80 at%Zr. Furthermore, glassy alloys were also synthesized in the range of 50 to 70 at%Ni, 5 to 35 at%Nb and 5 to 45 at%Zr. The maximum temperature interval of the supercooled liquid region was 51 K for Ni60Nb20Zr20 alloy. The tensile fracture strength and Vickers hardness of the glassy Ni60Nb20Zr20 alloy are 2160 MPa and 700, respectively. Wide ribbons with a width of 50 mm of amorphous Ni42Nb28Zr30 and glassy Ni60Nb20Zr20 alloys were produced at a circumferential velocity of the copper roller of 20 m/s.
TL;DR: In this paper, a micro-Vickers hardness measurement and transmission electron microscopy was performed on Mg-Li-Zn ternary alloys containing 4 to 13% Li and 4 to 5% Zn with or without dual phases.
Abstract: Precipitations in Mg–Li–Zn ternary alloys containing 4 to 13%Li and 4 to 5%Zn (in mass%) with or single phase, or with ( þ ) dual phases were investigated using a micro-Vickers hardness measurement and transmission electron microscopy. Age hardening in the phase alloy was found to occur, which was attributed to the precipitation of the stable (MgLiZn) phase with the following orientation relationships: 1⁄210 10 k 1⁄2110 , ð0001Þ k ð1 1 1Þ . In the ( þ ) phases alloy, the precipitation of the phase together with the metastable 0 (MgLi2Zn) phase occurred at grain boundaries between the and , and also and grains. The orientation relationships between the and 0 were as follows; ð0001Þ k ð01 1Þ 0 , 1⁄20 110 k 1⁄2111 0 . Age hardening in the alloy was caused by the precipitation of the 0 phase and over-aging was attributed to the precipitation of the and phases.
TL;DR: In this article, the appearance and disappearance of multistage martensitic transformation in aged Ni-rich Ti-Ni alloys depend on the heat treatment atmosphere, and it has been demonstrated with systematic experiments that the appearance of multi-stage transformation is an extrinsic nature, i.e., a kind of artifact during heat treatment.
Abstract: It has been demonstrated with systematic experiments that the appearance and disappearance of multistage martensitic transformation in aged Ni-rich Ti-Ni alloys depend on the heat treatment atmosphere. No multistage transformation occurs when the evaporation of Ti and Ni and/or the preferential oxidation of Ti in the specimen are prevented and the purification of heat treatment atmosphere in an evacuated quartz tube is achieved. The heterogeneity in precipitation morphology of Ti3Ni4 phase which is responsible for the multistage transformation can be suppressed with the regulation of heat treatment atmosphere as mentioned above. We have concluded that the multistage martensitic transformation in aged Ni-rich Ti-Ni alloys is an extrinsic nature, i.e., a kind of artifact during the heat treatment.
TL;DR: In this article, the influence of the combined addition of Mn and Sr results in modification of the needle-like phase as well as promotion of Chinese script and sludge morphology formation.
Abstract: The influence of Sr or Sr and Mn combined additions on the Fe-containing intermetallic compounds in Al-Si-Cu-Fe cast alloys has been investigated using Al-6.5%Si-3.5%Cu-1.0%Fe and Al-6.5%Si-3.5%Cu-1.0%Fe-0.3%Mn alloys (in mass%) with a similar composition to the 319 aluminum alloy. The results show that Sr successfully modifies the large, highly branched -needle-like phase ( :A l 5FeSi) into the individual, less-branched and finer one. The combined addition of Mn and Sr results in modification of the needle-like -phase as well as promotion of Chinese script and sludge morphology formation. The mechanism of the above morphological changes has been discussed in accordance with the mechanism of nucleation and growth of the -needle-like phase during solidification. Al-Si based cast alloys usually contain impurities or trace elements such as Fe, Mn, Cr that form preferentially high melting point and hard intermetallics with various morphol- ogies. The needle-like iron containing phase (-Al5FeSi) is the most harmful one for the mechanical properties of Al-Si based cast alloys. This phase, like most other intermetallic particles, is brittle. Its morphology is plate-like, appearing as needles in the optical micrographs. These characteristics, brittleness and plate-like morphology, greatly affect to decrease the strength and ductility of the cast alloys. It is, therefore, important to avoid or at least to control the formation of this phase. Mn is widely used as an alloying addition to neutralize the effect of iron and modify the needle-like -phase to less harmful morphologies. However, Mn is not always the best solution because it reacts with other elements existing in the melt and forms complex compounds. The major goal of this study is to find other effective elements to modify the -phase. Some limited work has been done on this subject. Sigworth 1) reported that the formation of Fe containing brittle phases were retarded in the Sr modified 319 alloy. Ouellet and Samuel 2) reported that the Sr modification of the Mg added 319 alloys caused the segregation of both the Al5Mg8Si6Cu2 and Al2Cu phases in the areas away from growing Al-Si eutectic regions. Samuel et al. 3) reported that the Sr addition led to the dissolution of more than two-thirds of the -needles and also to the modification of the Mg2Si particles in the Mg added 319 alloy. In this study, the influence of Sr or Sr and Mn combined additions on the intermetallic compound morphologies in an Al-Si-Cu-Fe cast alloy has been studied. The Fe concentration was as high as 1 mass% to make clear the morphological changes of the Fe- containing intermetallic compounds. 2. Experimental Procedure The alloys were melted in a graphite crucible by an electrical furnace with the composition of Al-6.5Si-3.5Cu- 1.0Fe (in mass%). Two categories of melt; 0.3%Mn-added and Mn-free melt were treated with 0.015% Sr addition. The alloys were cast into cast-iron and graphite molds to give different cooling rates. The effect of Sr on the microstructures was studied using an optical microscope and SEM. An image analysis method was utilized to measure the size and volume fraction of needle-like particles and number of intermetallic compounds per unit area. The chemical composition of the compounds was determined by an EDX method with a FE- SEM.
TL;DR: In this article, a numerical controlled full automatic friction welding machine was used to friction surface aluminum alloy and consumable rod with a 3 mm distance from the weld interface of the substrate.
Abstract: 5052 aluminum alloy used for substrate and consumable rod, was friction surfaced using a numerical controlled full automatic friction welding machine. Effects of the surfacing conditions on some characteristics of deposits were investigated. It was clearly observed that the circularly pattern appeared on the surface of deposit by the rotation of consumable rod. The deposit has a tendency to incline toward the advancing side further than center of deposit for the feed direction of consumable rod. This deviation accompanied the decrease of the rotational speed of consumable rod. The width of deposit increased with increasing friction pressure, and decreasing rotational speed of consumable rod. The thickness of deposit became thinner when the consumable rod was high revolution. The surfacing efficiency decreased with increasing friction pressure and rotational speed of consumable rod, but increased with increasing feed speed. Microstructure of the deposit was finer than that of the substrate and consumable rod. The softened area was recognized at 3 mm distance from the weld interface of substrate. The tensile strength of deposit increased with increasing friction pressure. The maximum tensile strength of deposits showed 88.8% of the base metal of substrate.
TL;DR: In this paper, a single-crystalline BaTi 2 O 5 was prepared by a floating zone method and the permittivity of the material was obtained at 748 K obeying the Curie-Weiss law at higher temperatures.
Abstract: Single crystalline BaTi 2 O 5 was prepared by a floating zone method. The permittivity of single crystalline BaTi 2 O 5 perpendicular to a (010) plane showed the maximum value of 20500.at 748 K obeying the Curie-Weiss law at higher temperatures. The permittivity perpendicular to (100) and (001) planes were 140 and 70, respectively almost independent of temperature. A transition temperature measured by a dilatometer was in agreement with a Curie temperature. The relationship between polarization and electrical field perpendicular to the (010) plane showed ferroelectric hysteresis. No hysteresis was observed in the direction perpendicular to (100) and (001) planes. The electrical conductivity perpendicular to the (010) was larger than those of (100) and (001) planes. The activation energy of electrical conductivity was 147 to 180 kJ mol -1 independent of directions.
TL;DR: In this paper, a finite element approach is presented which model the development of fraction transformed with time, in the beginning of the transformation, as a function of homogenisation temperature, as-cast microstructure and concentration of alloying elements.
Abstract: During the homogenisation process of Al-Mg-Si extrusion alloys, plate-like � -Al5FeSi particles transform to multiple rounded � - Al12(FeMn)3Si particles. The rate of thistotransformation determines the time which is required to homogenise the aluminium sufficiently for extrusion. In this paper, a finite element approach is presented which model the development of fraction transformed with time, in the beginning of the transformation, as a function of homogenisation temperature, as-cast microstructure and concentration of alloying elements. We treat thetotransformation mathematically as a Stefan problem, where the concentration and the position of the moving boundaries of the � andparticles are determined. For the boundary conditions of the model thermodynamic calculations are used (Thermo-Calc). The influence of several process parameters on the modelled transformed fraction, such as the temperature and initial thickness of theplates, are investigated. Finally the model is validated with experimental data.
TL;DR: In this paper, eutectic microstructures and silicon twin densities in samples modified by elemental additions of barium (Ba), calcium (Ca), yttrium (Y) and ytterbium (Yb) in an A356.0 alloy have been determined by optical microscopy, thermal analysis, X-ray diffractometry (XRD) and transmission electron microscopy (TEM).
Abstract: It is generally accepted that growth of eutectic silicon in aluminium-silicon alloys occurs by a twin plane re-entrant edge (TPRE) mechanism. It has been proposed that modification of eutectic silicon by trace additions occurs due to a massive increase in the twin density caused by atomic effects at the growth interface. In this study, eutectic microstructures and silicon twin densities in samples modified by elemental additions of barium (Ba), calcium (Ca), yttrium (Y) and ytterbium (Yb) (elements chosen due to a near-ideal atomic radii for twinning) in an A356.0 alloy have been determined by optical microscopy, thermal analysis, X-ray diffractometry (XRD) and transmission electron microscopy (TEM). Addition of barium or calcium caused the silicon structure to transform to a fine fibrous morphology, while the addition of yttrium or ytterbium resulted in a refined plate-like eutectic structure. Twin densities in all modified samples are higher than in unmodified alloys, and there are no significant differences between fine fibrous modification (by Ba and Ca) and refined plate-like modification (by Y and Yb). The twin density in all modified samples is less than expected based on the predictions by the impurity induced twining model. Based on these results it is difficult to explain the modification with Ba, Ca, Y and Yb by altered twin densities alone.