Search

In this study, changes in the microstructure, mechanical properties, and electrical conductivity of cast and extruded Al–Zn–Cu–Mg based alloys with the addition of Li (0, 0.5 and 1.0 wt.%) were investigated. The Al–Zn–Cu–Mg–xLi alloys were cast and homogenized at 570 °C for 4 hours. The billets were hot extruded into rod that were 12 mm in diameter with a reduction ratio of 38:1 at 550 °C. As the amount of Li added increased from 0 to 1.0 wt.%, the average grain size of the extruded Al alloy increased from 259.2 to 383.0 µm, and the high-angle grain boundaries (HGBs) fraction decreased from 64.0 to 52.1%. As the Li content increased from 0 to 1.0 wt.%, the elongation was not significantly different from 27.8 to 27.4% and the ultimate tensile strength (UTS) was improved from 146.7 to 160.6 MPa. As Li was added, spherical particles bonded to each other, forming an irregular particles. It is thought that these irregular particles contribute to the strength improvement.

In this study, microstructure and sintering behaviors of the gas-atomized Al-(25 or 30) Cr–xSi alloy (x = 5, 10 and 20 at.%) during spark plasma sintering (SPS) process were investigated. Gas-atomized alloy powders were manufactured using Ar gas atomizer process. These alloy powders were consolidated using SPS process at different temperature under pressure 60 MPa in vacuum. Microstructures of the gas-atomized powders and sintered alloys were analyzed using scanning electron microscopy (SEM) with energy–dispersive X-ray spectrometer (EDS), and transmission electron microscopy (TEM). Hardness of the SPS sintered alloys was measured using micro Vickers hardness tester. The Al–Cr–Si bulks with high Cr and Si content were produced successfully using SPS sintering process without crack and obtained fully dense specimens close to nearly 100% T. D. (Theoretical Density). The maximum values of the hardness were 834 Hv for the sintered specimen of the gas atomized Al–30Cr–20Si alloy. Enhancement of hardness value was resulted from the formation of the multi-intermetallic compound with the hard and thermally stable phases and fine microstructure by the addition of high Cr and Si.

The effect of addition of Mischmetal (MM) on the microstructure, electrical and thermal conductivity, and mechanical properties of the as-extruded Al-MM based alloys were investigated. The studied AlxMM alloys (where x = 0.2, 0.5, 1.0, 1.5, 2.0 and 5.0 wt.%) were cast and homogenized at 550 °C for 4 h. The cast billets were extruded into 12 mm bars with an extrusion ratio of 39 at 550 °C. The addition of MM resulted in the formation of Al11(Ce, La)3 intermetallic compounds and the area fraction of these intermetallic compounds increased with an increase in the MM content. The Al11(Ce, La)3 phase, which was distributed in the as-cast alloys, was crushed into fine particles and arrayed along the extruded direction during the extrusion process. In particular, these intermetallic compounds in the extruded Al-5.0MM alloy were distributed with a wide-band structure due to the fragmentation of the eutectic phase with a lamellar structure. As the MM content increased from 1.0 wt.% to 5.0 wt.%, the average grain size decreased remarkably from 740 to 73 μm. This was due to formation of Al11(Ce, La)3 particles during the hot extrusion process, which promoted dynamic recrystallization and suppression of grain growth. The electrical and thermal conductivity of the extruded alloys containing up to 2.0 wt.% MM were around 60.5% IACS and 230 W/m · K, respectively. However, the electrical and thermal conductivity of the extruded alloy with 5.0 wt.% MM decreased to 55.4% IACS and 206 W/m · K, respectively. As the MM content increased from 1.0 wt.% to 5.0 wt.%, the ultimate tensile strength (UTS) was improved remarkably from 74 to 119 MPa which was attributed to the grain refinement and formation of Al11(Ce, La)3 intermetallic compounds by the addition of MM.

High conductivity Al alloys are widely used for electric materials, heat exchangers, and heat dissipation parts such as electric conductors, transmission lines, communication cables, automobile wires and so on. In this study, the effects of Ca and Mn addition on the microstructure and mechanical properties of Al–0.3Cu–0.2Fe–0.15Si–0.15Zn alloys were investigated. The melt was held at 800 °C for 20 minutes and poured into a mold. The cast Al alloy was hot extruded with a rod having a diameter of 12 mm and a reduction ratio of 38:1. Al–0.3Cu–0.2Fe–0.15Si–0.15Zn–0.9Mn–0.4Ca alloy consists of Al, Al–(Fe, Mn)–Si, Al–(Fe, Mn) and Al–(Ca) intermetallic compounds. The formation of the intermetallic compound and this phase was broken in to small particles during extrusion. As the Ca content increased from 0 to 0.4 wt.%, the electrical conductivity of the extruded Al–0.3Cu– 0.2Fe–0.15Si–0.15Zn alloys increased by 57.3, 57.9 and 59.0 %IACS (International annealed copper standard). Al–0.3Cu–0.2Fe–0.15Si–0.15Zn–0.9Mn alloy with element additions of Ca, ultimate tensile strength was decreased from 178.3 to 163.2 and 151.8 MPa. However, the elongation was improved to 18.6, 21.6 and 23.15%.

In this study, we investigate the microstructure and mechanical properties of as-extruded Al-1.0RE alloys. The molten Aluminum alloy was maintained at 800 °C and then poured into a mould at 200 °C. Aluminum alloys were hot-extruded into a rod measuring 12 mm thick with a reduction ratio of 38:1. The microstructure and electric conductivity properties of as-extruded Al-1.0RE alloy under different annealing processes were investigated and compared. After extrusion, the intermetallic compound having a needle shape in the cast state was finely decomposed based on the direction of extrusion. Significant changes in the microstructure were detected after annealing at 500 °C with fragmentation and sphering of eutectic particles. The annealing temperature of Al-1.0RE alloy increased proportionally to the electrical conductivity. The formation of Al-RE intermetallic compounds increases the electrical conductivity and improves the mechanical properties of the alloy through precipitation hardening.

Microstructure and texture of P-type 75%Sb₂Te₃-25%Bi₂Te₃ alloy fabricated by using gas-atomization and extrusion processes was investigated. The microstructure of the gas-atomized powders exhibited fine grains with needle shape. After hot extrusion, grain size was characterized by fine and equiaxed grains due to dynamic recrystallization by severe deformation. (0001) basal planes of the extruded specimens were preferentially orientated parallel to extrusion direction. As extrusion temperature, fraction of the basal planes was increased.

In this work, Al-0.15Si-0.2Fe-0.3Cu-0.9Mn alloys with different Zn addition (0, 0.15 and 0.3 wt%) were melted and extruded at 200 °C. The effect of Zn on the microstructure, texture evolution and mechanical properties of Al-0.15Si-0.2Fe-0.3Cu-0.9Mn alloys was investigated using scanning electron microscope (SEM), equipped with energy-dispersive X-ray spectrometry (EDS) and electron backscatter diffraction (EBSD) and in the present study. In order to evaluate the mechanical properties, we implemented the tensile tests by a universal material test machine. Al-0.15Si-0.2Fe- 0.3Cu-0.9Mn-xZ resulted in the formation of Al-(Fe, Mn)-Si and Al-(Fe, Mn) intermetallic compounds. The formation of the intermetallic compound and this phase was broken in to small particles during extrusion. The ultimate strength and elongation of the as-extruded Al-0.15Si-0.2Fe-0.3Cu- 0.9Mn alloy were 96.51 MPa and 34.01%, while those of the Al-0.15Si-0.2Fe-0.3Cu-0.9Mn-0.3Zn alloy were 99.08 MPa and 36.21%, respectively. Al-0.15Si-0.2Fe-0.3Cu-0.9Mn alloys with Zn addition resulted in improving the strength with no reduction in elongation.

A significant enhancement in corrosion resistance by Y microalloying was achieved for the Mg–8Sn–1Zn–1Al (wt%) alloy in the extruded condition. Average corrosion rates obtained by immersion tests in 0.6 M NaCl solution at 25 °C were 4.2 and 12.7 mm y−1 for the alloys with and without microalloying with 0.04 wt% Y, respectively. Microstructural investigations indicated that the enhanced corrosion resistance is a result of a transition in a type of second-phase particles toward lowering the difference in electrochemical nobility between the α-Mg and these particles, thereby reducing the susceptibility of the alloy to microgalvanic corrosion.

Microstructure and properties of Al–2 wt.%Zn–1 wt.%Cu–xMg (x = 0.1, 0.3, 0.5, 0.7 wt.%) alloy extrusion materials were investigated. The lattice constants for the (311) plane increased to 4.046858, 4.048483, 4.050114 and 4.051149 Å with the addition of 0.1, 0.3, 0.5, and 0.7 wt.% of elemental Mg. The average grain size of the as-extruded Al alloys was found to be 328.7, 297.7, 187.0 and 159.3 μm for the alloys with 0.1, 0.3, 0.5, and 0.7 wt.% Mg content, respectively. The changes in the electrical conductivity by the addition of elemental Mg in Al–2 wt.%Zn–1 wt.%Cu alloy was determined, and it was found that for the addition of 0.1, 0.3, 0.5, and 0.7 wt.% Mg, the conductivity decreased to 51.62, 49.74, 48.26 and 46.80 %IACS. The ultimate tensile strength of Al–2 wt.%Zn–1 wt.%Cu–0.7 wt.%Mg alloy extrusion was increased to 203.55 MPa. Thus, this study demonstrated the correlation between the electrical conductivity and strength for the Al–2 wt.%Zn–1 wt.%Cu–xMg alloys.

Niobium-titanium alloy is attractive materials for industrials as a superconducting magnets to high critical magnetic field and supercurrent density at -283 °C. The Nb-Ti alloy has been shown in earlier work to exhibit Van Gosh Sky microstructures. They may also be accentuated by plastic deformation due to work and temperature exposure during deformation. In order to miniaturize the magnet generating the same magnetic field, it is necessary to increase the critical current density of the superconducting wire. When fabricating superconducting wires, it is important to increase critical current density by optimizing processing and annealing conditions. When the α-phase of the Ti rich phase is uniformly precipitated by the heat treatment, the non-superconducting α-phase is dispersed in the superconducting Nb-Ti matrix. It becomes a pinning point that serves to fix the magnetic flux, which improves the critical current density. Also, if the shape of the precipitate is changed by machining, the superconducting and non-superconducting characteristics are further improved. In the present study, we studied the fraction of α-Ti phase of strain amount through groove rolling and heat treatment. The specimens were processed by groove rolling at room temperature and strain of 2.0, 3.16, 4.28 and 5.57. A microstructural analysis of the Nb-Ti alloys was performed by field emission scanning electron microscopy (FESEM).

We investigated the effects of Al-5.0wt%Ti-1.0wt%B addition on the microstructure and mechanical properties of the as-extruded Al-0.15wt%Si-0.2wt%Fe-0.3wt%Cu-0.15wt%Zn-0.9wt%Mn based alloys. The Aluminum alloy melt was held at 800 °C and then poured into a mould at 200 °C. Aluminum alloys were hot-extruded into a rod that was 12 mm in thickness with a reduction ratio of 38:1. AlTiB addition to Al-0.15Si-0.2Fe-0.3Cu-0.15Zn-0.9Mn based alloys resulted in the formation of Al3Ti and TiB2 intermetallic compounds and grain refinement. With increasing of addition AlTiB, ultimate tensile strength increased from 93.38 to 99.02 to 100.01 MPa. The tensile strength of the as-extruded alloys was improved due to the formation of intermetallic compounds and grain refinement.

Accumulative roll-bonding (ARB) is the most appropriate process for sheet-shaped materials because it can be carried out readily by utilizing the conventional rolling apparatus. In this study, a nanostructured AA1050/AA5052 Al alloy sheet was successfully fabricated by four-layer stack ARB process. The ARB of AA1050 and AA5052 alloy sheets was performed up to 6 cycles without a lubricant at ambient temperature. The sample fabricated by the ARB was a multi-layer aluminum alloy sheet in which AA1050 and AA5052 layers are alternately stacked. The layer thickness of the each alloy became thinner and elongated to the rolling direction with the number of ARB cycles. The grain size decreased with increasing of the number of ARB cycles, after 6 cycles it became about 180 nm in thickness. The fraction of high angle grain boundaries increased with the number of ARB cycles. The tensile strength also increased with the ARB, it reached 305 MPa which is about 2.1 times that of the as-received AA1050. The mechanical properties of a multi-layer AA1050/AA5052 alloy fabricated by the ARB were compared to those of the other materials.

Thermal properties and microstructure of Al-4 wt.% Zn-2 wt.% Cu–x (x = 2 wt%. Mg, 2 wt%. Sn, 0.7 wt.% Mg-0.7 wt.% Sn-0.7 wt.% Ca) alloys on cast and extrusion have been investigated with extrusion temperature of 400 °C. Al-4 wt.% Zn-2 wt.% Cu alloy was composed of Al and Al2Cu phases. By adding Mg contents, Al2Mg3Zn3 phase was increased and Al2Cu phase was decreased respectively. During hot extrusion, elongated in the extrusion direction because of severe deformation. The thermal conductivity with temperature and composition of as-extruded Al-4 wt.% Zn-2 wt.% Cu–x alloys decreases with adding 2 wt.% Mg, 2 wt.% Sn contents from 190.925 and 196.451 W/mK but thermal properties of addition of 0.7 wt.% Mg-0.7 wt.% Sn-0.7 wt.% Ca element slightly reduced from 222.32 to 180.775 W/mK. The ultimate tensile strength (UTS) for Al-4 wt.% Zn- 2 wt.% Cu alloy was 121.67 MPa. By adding 2 wt.% Mg contents, tensile strength was dramatically increased with 350.5 MPa.

Aluminum and its alloys are used in a wide range of industrial applications from low density, high strength and a variety of structural materials. In this study, the effects of Ca addition on the microstructure and mechanical properties of Al-1wt.%RE alloys were investigated. The melt was held at 800 °C for 20 minutes and poured into a mold. The cast Al alloy was hot extruded with a rod having a diameter of 12 mm and a reduction ratio of 38:1. Al-1wt.%RE alloy consists of Al, Al11RE₃ phase. The Al₂Ca phase is increased by increasing the Ca content to 0.2 to 0.4 wt.%. As the Ca content increased from 0 to 0.4 wt.%, the average grain size of the extruded Al alloy decreased by 739.8, 400.8 and 155.0 μm. The tensile strengths were increased to 74.25, 76.53, and 79.52 MPa. The electrical conductivity of Al-RE alloy with Ca addition decreased to 60.32, 58.15 and 57.89% IACS.

The exothermic reduction of oxides mixture (MoO3+2SiO2) by magnesium in NaF melt enables the synthesis of nanocrystalline MoSi2 powders in near-quantitative yields. The combustion wave with temperature of about 1000–1200 °C was recorded in highly diluted by NaF starting mixtures. The by-products of combustion reaction (NaF and MgO) were subsequently removed by leaching with acid and washing with water. The as-prepared MoSi2 nanopowder composed of spherical and dendritic shape particles was consolidated using the spark plasma sintering method at 1200–1500 °C and 50 MPa for 10 min. The result was dense compacts (98.6% theoretical density) possessing submicron grains and exhibiting hardness of 8.74–12.92 GPa.

The microstructure and mechanical properties of as-extruded Al-0.1 wt%Si-0.2 wt%Fe- 0.4 wt%Cu-0.04 wt%Zr-xMn-xAlTiB (x = 1.0 wt%) alloys under various annealing processes were investigated and compared. After the as-cast billets were kept at 400 °C for 1 hr, hot extrusion was carried out with a reduction ratio of 38:1. In the case of the as-extruded Al-Si-Fe-Cu-Zr alloy at annealed at 620 °C, large equiaxed grain was observed. When the Mn content is 1.0 wt%, the phase exhibits a skeleton morphology, the phase formation in which Mn participated. Also, the volume fraction of the intermetallic compounds increased with Mn and AlTiB addition. For the Al-0.1Si-0.2Fe-0.4Cu-0.04Zr alloy with Mn and AlTiB addition from 1.0 wt%, the ultimate tensile strength increased from 100.47 to 119.41 to 110.49 MPa. The tensile strength of the as-extruded alloys improved with the addition of Mn and AlTiB due to the formation of Mn and AlTiB-containing intermetallic compounds.

Magnesium and its alloys are potential candidates for many automotive and aerospace applications due to their low density and high specific strength. However, the use of magnesium as wrought products is limited because of its poor workability at ambient temperatures. Mg-Li alloys containing 5-11 wt.% Li exhibit a two-phase structure consisting of a α (hcp) Mg-rich phase and a β (bcc) Li-rich phase. Mg-Li alloys with Li content greater than 11 wt.% exhibit a single-phase structure consisting of only the β phase. In the present study, we studied the effects of Y addition on the microstructure and mechanical properties of Mg-11Li-6Zn-0.6Zr-0.4Ag-0.2Ca based alloys. The melt was maintained at 720 °C for 20 min and poured into a mold. Then, the as-cast Mg alloys were homogenized at 350 °C for 4 h and were hot-extruded onto a 4-mm-thick plate with a reduction ratio of 14:1. The as-cast Mg-11Li-6Zn-0.6Zr-0.4Ag-0.2Ca-xY (x 0, 1, 3, and 5 wt.%) alloys were composed of α-Mg, β-Li, γ-Mg2Zn3Li, I-Mg3YZn6, W-Mg3Y2Zn3, and X-Mg12YZn phases. By increasing the Y content from 0 to 5 wt.%, the composition of the W-Mg3Y2Zn3 phase increased. With increasing Y content, from 0 to 1, 3, and 5 wt.%, the average grain size and ultimate tensile of the as-extruded Mg alloys decreased slightly, from 8.4, to 3.62, 3.56, and 3.44 μm and from 228.92 to 215.57, 187.47, and 161.04 MPa, respectively, at room temperature.

In this study, the effects of heat-treatment conditions on the densification, microstructure, and magnetic properties of Fe powder were investigated. The oxygen content of the Fe powders heat-treated in Ar and Ar-H2 atmosphere was much lower than that of the Fe powder heat-treated in air atmosphere. The density of the compacts of the Fe powder heat-treated in Ar and Ar + H2 atmosphere was higher than that of the compacts of Fe powders heat-treated in air. Oxygen content in the heat-treatment conditions played a significant role in the improvement of the densification and magnetic properties.

Effects of yttrium (Y) addition on mechanical properties and fracture behaviors of the as-extruded Mg-Al-Ca based alloys at elevated temperature were investigated by a tensile test. After hot extrusion, the average grain size was refined by Y addition and eutectic phases were broken down into fine particles. Y addition to Mg-5Al-3Ca based alloy resulted in the improvement of strength and ductility at elevated temperature due to fine grain and suppression of grain growth by formation of thermally stable Al2Y intermetallic compound.

The microstructure of the as-cast Mg-5Al-3Ca-2Nd-xDy alloys consists of α-Mg matrix, (Mg, Al)2Ca eutectic phase, Al-Nd and Al-Dy intermetallic compounds. α-Mg matrix morphology was changed from dendritic to equiaxed with the increase Dy addition. And grain size was remarkably refined. As Dy content was increased, yield strength was improved due to the refined grains and the homogeneous distribution of Al-Dy phase.

Aluminum and its alloys, due to their low density, high specific strength and high corrosion resistance amongst various structural materials, are used in a wide range of industrial applications for different aqueous solutions. In the present study, we studied effects of Ce addition on microstructure and mechanical properties of Al-2Li-1Cu-0.8Mg-0.1Zr alloys. The melt was held at 780 °C for 20 min and poured into a mold. And as-cast Al alloys were hot-extruded into a plate that was 4 mm in thickness with a reduction ratio of 14:1. The extruded plates were held at 540 °C for 4 hr in water quenching to solution treatment them. As-extruded Al-2Li-1Cu-0.8Mg-0.1Zr-xCe (x = 0.3, 0.6, 0.9 and 1.2 wt.%) alloys are composed of Al, AlLi, AlCuLi and Al11Ce3 phases. By increasing the Ce content from 0 to 1.2 wt.%, the Al11Ce3 phase is increased, after solution treatment the AlLi and AlCuLi phases are decreased. With increasing Ce addition from 0 to 1.2 wt.%, the average grain size of the as-extruded Al alloys were decreased slightly from 100.7, 113.74, 84.3, 74.7 and 61.7 μm and ultimate tensile strength was decreased slightly from 267.59, 264.92, 237.40, 220.93 and 207.83 MPa at room temperature. After solution treatment, ultimate tensile strength was measured with 205.13, 198.12, 195.50, 198.27 and 208.01 MPa at room temperature.

In this study, the gas-atomized Cu-15%Ga alloy powder was consolidated by cross-roll rolling using copper can without crack and oxidation, where the roll axis was tilted by 5 degrees against TD in the RD-TD plane. Microstructures of formed Cu-15%Ga alloy were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and optical microscopy (OM). Density of the cross-roll rolled specimens was measured using Archemeded method. Also, the porosity was examined by an image analyzer. The porosity of the cross-roll rolled samples with rolling reduction of 60% was approximately 6.7 times lower than that of the CR-rolled samples at 40% at a rolling temperature to 850 degrees C. The specimen obtained with 5 degrees of cross-roll rolling degree and 60% of rolling reduction ratio at 850 degrees C was above 99% to the theoretical density and an average grain size was 19.2 μm.

In this study, effects of Nd addition on mechanical properties and fracture behaviors of as-extruded Mg-5Al-3Ca based alloy were investigated by a tensile test at elevated temperatures. For all temperatures, addition of Nd elements resulted in further increase of strength both yield and ultimate strength compared to the Mg-5Al-3Ca alloy. At 150°C, the ductility in Nd-added alloys is lower than that of no-Nd addition alloy. However, at 250°C, the ductility in Nd-added alloys is improved for no-Nd addition alloy because of fine grain and suppression of grain growth by formation of thermally stable Al2Nd intermetallic compounds.

We investigated the effects of Ag addition on the microstructure and mechanical properties of hot-extruded Mg–6Zn–2Sn–0.4Mn-based alloys. Ag addition resulted in the formation of fine submicron-sized Mg–Ag particles, grain refinement, and weaker basal texture in the alloys. The Ag-containing extruded alloys had better mechanical properties than the alloys without Ag. The ultimate tensile strength (UTS) and elongation of alloys containing 1 wt.% Ag were 352 MPa and 19%, respectively.

For the Mg–Sn–Al alloys, the ultimate strength (UTS) of an extruded Mg–9wt.%Al–2wt.%Sn alloy reached 390 MPa. TEM observation indicated that plate-like Mg 17 Al 12 precipitates having Burgers orientation relationship with the matrix are responsible for the strength. This alloy also exhibits an age hardening behavior: the peak hardness appears after 15–20 h of heat treatment at 473 K. On the other hand, the UTS of the Mg–Mg–Sn–Zn alloys are on the order of 300 MPa. The precipitates in these alloys are composed of the Mg 2 Sn and MgZn 2 particles. It was found that these phases often precipitate together, suggesting that the MgZn 2 phase can act as a nucleation sites for Mg 2 Sn.

In the present study, the samples were rolled by two pass rolling with the cross-roll rolling mill in order to be affected only by the shear strain for the surface and center layers of the sheets. The microstructures and texture evolution of the specimen for the surface and center layers of the sheet were investigated using optical microscopy (OM) and electron backscatter diffraction (EBSD) before and after heat treatment.

The objective of this study was to investigate the cross-roll rolling process effects on microstructures and mechanical properties of AZ31 Mg sheet about rolling angle, in which the roll axes were tilted 0 , 2.5 , 5 and 7.5 away from the transverse direction. Three-dimensional FEM simulation proved that increasing the cross-roll angle, the through-thickness variation of effective strains decreases extremely. The cross-roll rolled and subsequently annealed samples have the uniform and fine grain size at whole thickness layers with increasing the cross-roll angle from 0 to 7.5 . The result of tensile test discloses that while the increase in cross-roll angle can scarcely affect on the strength of samples, it can improve the formability of samples remarkably. [doi:10.2320/matertrans.M2011260]

The microstructure of as-cast Mg-xAl-2Sn alloys consists of an α-Mg matrix, a Mg17Al12 eutectic phase and a Mg2Sn phase. In as-cast alloys, the Mg17Al12 eutectic phase was located at along grain boundaries. The eutectic phase of the extruded alloys was elongated in the extrusion direction and crushed into fine particles because of deformation during hot extrusion, and the grain size was refined with an increased Al content. The maximum values of the yield strength and tensile strength were 240 MPa and 300 MPa at 9 wt.% containing Al element, respectively.

In the present work, the effect of Nd addition on microstructure change, precipitation behaviours and mechanical properties, of Mg-5Sn-3Ca based alloys were investigated. With increasing of Nd addition, size of the Mg-Sn-Ca ternary phases with fine needle shape (A-type) was decreased and volume fraction of these phase were increased. As Nd was increase from 0.5, 1.0 and 3.0 wt.%, size and volume fraction of Mg2Sn with coarse needle shape phase (B-type) was decreased. However, in 3.0 wt.% Nd containing alloy, size of these Mg2Sn phase was smaller than that of 0.5 and 1.0 wt% Nd addition alloy and volume fraction of these phase was decreased.

The effect of Ca addition on microstructure change, precipitation behaviours and mechanical properties, in the present work, of Mg-Sn based alloys were investigated. With increasing of Ca additions, size of the Mg-Sn-Ca ternary phases (A-type) with fine needle shape was decreased and volume fraction of these phase were increased. As Ca was increase from 1 wt.%, 2 wt.%, size and volume fraction of Mg2Sn with coarse needle shape phase (B-type) was increased. However, in 3 wt.% Ca containing alloy, size of these Mg2Sn phase was smaller than that of 2 wt% Ca addition alloy and volume fraction of these phase was decreased.

In this paper, we suggested the new standards of motor design in using of Soft magnetic composite (SMC) material. Previous motor design in using of SMC material executed the same procedures of silicon steel. These procedures assumed that all places of material have the same density distribution and B-H curves. But we showed that the SMC material has inequality density distribution. By using powder forming analysis with FEM analysis, we showed that difference of density distribution could not be avoided because of the shear stress on powder, surface of the mold and punch. Therefore the magnetic characteristic was not the same in all places of material. So, we suggested the new method of motor design which considered the inequality density distribution in using of SMC material. And we compared previous method results and new method results and showed the differences of the result values. The density deviation of the SMC motor core was 5.8% and efficiency deviation was 3%. Especially the output value was different above 11% when we got the results by using previous method.

The as-cast microstructure of Mg-5Al-3Ca-xY alloy consists of dendritic � -Mg matrix, (Mg, Al)2Ca eutectic phase and Al2Y intermetallic compounds. These two kind of (Mg, Al)2Ca compounds were observed: coarse irregular-shape structure at grain boundary and fine needle-shape structure in the � -Mg matrix grain. This (Mg, Al)2Ca phase of the extruded alloys was elongated to extrusion direction and size of this phase was refined comparing with that of as-cast alloys because of severe deformation during hot extrusion. Maximum yield and ultimate strength value of extruded alloys was 326 and 331 MPa at Mg-5Al-3Ca-3Y alloy, respectively. From these results, it is conclusively demonstrated that Y additions on Mg-5Al-3Ca alloy have more effect to improve mechanical properties. [doi:10.2320/matertrans.MC200777]

The as-cast microstructure of Mg-5Al-3Ca-xNd alloys consists of equiaxed α-Mg matrix, (Mg, Al) 2 Ca eutectic phase and Al-Nd rich intermetallic compounds. With the increase of Nd addition, α-Mg matrix morphology was changed from dendritic to equiaxed grains due to suppression of grain growth by formation of homogeneous intermetallic compounds containing Nd dispersed at grain boundary and α-Mg matrix. And the grain size of as-cast alloys was decreased as addition of Nd was increased. This eutectic phase of the extruded alloys was elongated to extrusion direction and size of this phase was redined comparing to that of as-cast alloys because of severe deformation during hot extrusion. Maximum yield and ultimate tensile strength value of the as-extruded alloys was 322 and 335 MPa at Mg-5Al-3Ca-2Nd alloy, respectively.

The aims of this research are to investigate the effect of Sm addition in Mg-Al-Ca alloys on microstructure and mechanical properties. Sm addition to Mg-5Al-3Ca based alloys results in the change from dendritic to equiaxed grain morphorlogy and formation of Al-Sm rich itermetallic compounds at grain boundary and α-Mg matrix. And these Al-Sm rich intermetallic compounds were dispersed homogeously and stabilized at high temperature. And maximum yield and ultimate strength value was obtained at Mg-5Al-3Ca-2Sm alloys at elevated temperature because of homogeneous dispersion of stable Al-Sm rich intermetallic compound at high temperature.

In this study, we try to investigate the asymmetric rolling process affects microstructure, texture and formability of AZ31 Mg sheet. The deformation twins are clearly apparent, small and recrystallized grains are visible along some grain boundary and twinned regions in the as-rolled both samples. The symmetrically rolled sample tended to show peak inclined to the rolling direction. On the other hand, the asymmetrically rolled sample tended to show peak slightly inclined to the transverse direction. From the pole figure observation by EBSD, the intensity decrease of basal fiber texture after asymmetric rolling should be attributed to the severe shear strain induced during asymmetric process. The Erichsen value was measured to be 6.5 for asymmetrically rolled sample and 5.2 for symmetrically rolled sample.

The aims of this study are to investigate the effect of Y (yttrium) addition in the Mg-Al- Ca alloys on microstructure and mechanical properties. In additions, the alloys were solution treated in order to achieve a better understanding of the precipitation mechanisms. The as-cast microstructure of Mg-5Al-3Ca alloy and Mg-5Al-3Ca-xY alloys contains dendritic α-Mg matrix and eutectic intermetallic compound at grain boundary. The hardness values of Mg-Al-Ca alloy with Y additions were slightly increased than that of Mg-Al-Ca with no Y addition. It is because of reduction of α-Mg phase and presence of (Mg,Al)2Ca and Al-Y rich intermetallic phase at grain boundary and α-Mg matrix grains. Also, hardness value of yttrium (Y) containing alloys was increased with increasing Y contents. Compared to Mg-5Al-3Ca alloy, maximum strength and yield strength of the alloys with Y additions have slightly increased with increasing Y additions in the case of as-cast samples.

A new life function based on a model for the creep–fatigue life prediction in terms of stress relaxation during hold time has been proposed. From the concept that the reduction of fatigue life with hold time is due to the creep effect of stress relaxation that results in the additional energy dissipation in the hysteresis loop, the relaxed stress range is suggested to be a creep–fatigue damage function. The plastic strain range (Δɛp) exhibiting a functional correlation of both strain and time requires experimental efforts following Coffin–Manson relationship [L.F. Coffin Jr., Trans. ASME 76 (1954) 931–950; S.S. Manson, NASA Technical Note 2933, NASA Research Center, Cleveland, OH, 1954] upon applied creep–fatigue conditions. After the new concept was applied to the relationship, all the Coffin–Manson plots at the various levels of hold time under strain-controlled fatigue tests were identified as a linear relationship with relaxed stress range (Δσ) and fatigue life (Nf). The normalized creep–fatigue life prediction model, which can be applied to high temperature materials regardless of the fracture morphology is presented in view of a real situation.

Si and Er co-doped SiO2 films were fabricated by radio-frequency (RF) magnetron sputtering technique with a Si-Er-SiO2 target. The optical gain of 0.7 dB/cm was confirmed by the direct pumping of Er3+ using the laser diode (LD) of 980 nm in wavelength and 60 mW in output power. On the contrary, the pumping Si-nanocrystals by the Hg lamp 365 nm (1.5 W/cm2) induced the absorption loss above 1.48 μm region in wavelength, which was attributed to the free carrier absorption of Si-nanocrystals.

Mg97Zn1Y2 alloy powders were prepared from gas atomization process, followed by consolidation using spark plasma sintering (SPS) process. The atomized Mg97Zn1Y2 alloy particles were entirely spherical in shape and dendrite microstructure. The compacts sintered by SPS process have values more than 99% of theoretical density. The compressive yield strength was decreased as sintering temperature increased. It is found that the compressive strength showed the maximum value of 303MPa at the sintered specimen under load of 250MPa at 350°C.

Although glass wool and polyurethane foam are the most widely used sound-absorber and insulating materials, there are some critical problems related to the environmental issues. In this reason, there is a lot of attention on the aluminum foam as a sound absorption material, therefore, in this research, sound absorption and transmission loss properties were studied. The results showed that low density aluminum foam performed better in both sound absorption and transmission loss and the properties were improved as increased air cavity and space.

The aims of this study ares to investigate the microstructure evolution of AZ31 Mg alloys with normal rolling and different speeds rolling during hot rolling affects microstructure, texture and mechanical properties of AZ31 Mg alloy. In the microstructures of as-rolled both samples, twins are clearly apparent, small and recrystallized grains are visible along some grain boundary and twinned regions. The tensile strength and yield strength of DSR sample were slightly higher than that of NR sample. Also, in the case of the NR sample, tensile strength indicated different values to the rolling directions. From this result, NR sample compared to DSR sample strongly indicated to the plastic anisotropy tendency. Therefore, it is noted that DSR sample could be presented to the good formability, comparing to the NR sample. DSR samples deformed at 473K and 523K could be perfectly formed, indicating the potential application of the DSR process to improve formability of the Mg alloys at warm temperatures.

As samarium addition was increased, α- Mg matrix morphology was changed from dendritic to equiaxed grains and average value of grain size was decreased from 101.6㎛ to 39.3㎛. Samarium addition to Mg-5Al-3Ca based alloys resulted in the formation of Mg-Al-Sm thernary intermetallic compounds at grain boundarys and α-Mg matrix grains. In these alloys, two kinds of eutectic structure were observed; coarse irregular-shape structure at grain boundary and fine needle-shape structure in the α-Mg matrix grain. It is found that the yield strength and ultimate strength showed the maximum value of 109.1MPa and 139.3 at Mg-5Al-3Ca-2Sm alloy, respectively.