Microstructure and mechanical properties of ZA62 Mg alloy by equal-channel angular pressing

The Mg-6Zn-2Al alloy was processed by ECAP and microstructure and mechanical properties of the alloy before and after ECAP were studied. The results revealed that the microstructure of the ZA62 alloy was successfully refined after two-step ECAP (2 passes at 473 K and 2-8 passes at 423 K). The course bulk interphase of Mg₅₁Zn₂₀ was crushed into fine particles and mixed with fine matrix grains forming “stripes” in the microstructure after the second step of ECAP extrusion. A bimodal microstructure of small grains of the matrix with size of ∼0.5 μm in the stripes and large grains of the matrix with size of ∼2 μm out of stripes was observed in the microstructure of samples after 4-8 passes of ECAP extrusion at the second step. The mechanical properties of the alloy studied were significantly improved after ECAP and the highest yield strength and elongation at room temperature were obtained at the samples after 4 and 8 ECAP passes at the second step, respectively. Tensile tests carried out at temperature of 473 K to 573 K and strain rate of 1 × 10⁻³ s⁻¹ to 3 × 10⁻² s⁻¹ revealed that the alloy after 8 ECAP passes at the second step showed superplasticity and the highest elongation and strain rate sensitivity (m-value) reached 520% and 0.45, respectively.     

Constitutive modeling for the dynamic recrystallization evolution of AZ80 magnesium alloy based on stress-strain data

In order to improve the understanding of the dynamic recrystallization (DRX) behaviors of as-cast AZ80 magnesium alloy, a series of isothermal upsetting experiments with height reduction 60% were performed at the temperatures of 523 K, 573 K, 623 K and 673 K, and the strain rates of 0.01 s⁻¹, 0.1 s⁻¹, 1 s⁻¹ and 10 s⁻¹ on a Gleeble 1500 thermo-mechanical simulator. Dependence of the flow stress on temperature and strain rate is described by means of the conventional hyperbolic sine equation. By regression analysis, the activation energy of DRX in the whole range of deformation temperature was determined to be Q = 215.82 kJ mol⁻¹. Based on dσ/d? versus σ curves and their processing results, the ?ow stress curves for AZ80 magnesium alloy were evaluated that they have some characteristic points including the critical strain for DRX initiation (?_c), the strain for peak stress (?_p), and the strain for maximum softening rate (?*), which means that the evolution of DRX can be expressed by the process variables. In order to characterize the evolution of DRX volume fraction, the modified Avrami type equation including ?_c and ?* as a function of the dimensionless parameter controlling the stored energy, Z/A, was evaluated and the effect of deformation conditions was described in detail. Finally, the theoretical prediction on the relationships between the DRX volume fractions and the deformation conditions were validated by the microstructure graphs.     

Hot working parameters and mechanisms in as-cast Mg-3Sn-1Ca alloy

The hot working characteristics of as-cast Mg-3Sn-1Ca alloy have been studied using processing-map technique and the kinetic rate equation. The map exhibited two domains; one in the lower strain rate range (0.0003-0.01 s^− 1) and the other in the higher strain rate range (0.1-10 s^− 1)—both falling in the same temperature range of 350-550 s^− 1. Hot extrusion at 500 °C and a speed corresponding to an average strain rate of 3 s^− 1 exhibited dynamically recrystallized microstructure. The estimated apparent activation energy values are higher than those for self-diffusion in pure magnesium suggesting that the large volume fraction of MgSnCa intermetallic particles causes significant back stress.     

Enhanced superplasticity of 1 wt.%Ca-AZ80 Mg alloy with ultrafine grains

Ultrafine grained (UFG) 1 % Ca-AZ80 (1CaAZ80) alloy in sheet form could be fabricated by means of high-ratio differential speed rolling (HRDSR) technique. During the rolling, the grain size was markedly reduced from 11.5 to 0.8 μm, and Al₂Ca particles were broken up to smaller ones and dispersed into the matrix. The UFG 1CaAZ80 alloy exhibited a high strength (yield stress = 340 MPa) at room temperature and excellent superplasticity at elevated temperatures. A maximum elongation of ∼ 700% was obtained at 2 × 10^− 4 s^− 1 − 523 K. The currently proposed HRDSR process opens a new opportunity of producing high-performance superplastic magnesium alloy sheets.     

Deformation and strain rate sensitivity of a Zr-Cu-Fe-Al metallic glass

The deformation behaviour of Zr₆₅Cu₂₀Fe₅Al₁₀ bulk metallic glass has been studied at room temperature under uniaxial compression conditions at the strain rate of 5 × 10⁻⁴ s⁻¹ and performing jump tests for the strain rates (SR) ranging between 5 × 10⁻⁶ s⁻¹ and 5 × 10⁻² s⁻¹. The alloy always shows the formation of shear bands and exhibits serrated flow. In the SR range of 5 × 10⁻⁶ to 5 × 10⁻³ s⁻¹ absence of strain rate sensitivity within the experimental error is observed. However, when the SR changes from 5 × 10⁻³ s⁻¹ to 5 × 10⁻² s⁻¹ the alloy exhibits a negative strain rate sensitivity of −0.0026. The number of shear bands on the side view appears to be correlated with the range of stress softening from the maximum stress to the stress at which the sample fails.     

Polycrystalline films of tungsten-doped indium oxide prepared by d.c. magnetron sputtering

Electrical and optical properties of polycrystalline films of W-doped indium oxide (IWO) were investigated. These films were deposited on glass substrate at 300 °C by d.c. magnetron sputtering using ceramic targets. The W-doping in the sputter-deposited indium oxide film effectively increased the carrier density and the mobility and decreased the resistivity. A minimum resistivity of 1.8 × 10^− 4 Ω cm was obtained at 3.3 at.% W-doping using the In₂O₃ ceramic targets containing 7.0 wt.% WO₃. The 2.2 at.% W-doped films obtained from the targets containing 5.0 wt.% WO₃, showed the high Hall mobility of 73 cm² V^− 1 s^− 1 and relatively low carrier density of 2.9 × 10²⁰ cm^− 3. Such properties resulted in novel characteristics of both low resistivity (3.0 × 10^− 4 Ω cm) and high transmittance in the near-infrared region.     

Superplastic behavior of a TiAl alloy in its as-cast state

Superplastic behavior of a TiAl alloy was investigated in a temperature range between 800 and 1000°C and at a strain rate of 1×10⁻⁴ s⁻¹. The results show that the present alloy possesses very good superplasticity even in its as-cast state. A tensile elongation of 628% was obtained at 850°C. The observed superplastic behavior can be explained by the formation of a fine microstructure containing a metastable β-phase during solidification.     

The microstructure,tensile, and shear deformation behavior of an AZ31 magnesium alloy after extrusion and equal channel angular pressing

The shear punch testing (SPT) technique and the uniaxial tension tests were employed to evaluate the mechanical properties of the equal channel angularly pressed (ECAPed) AZ31 magnesium alloy. After extruding, the material was ECAPed for 1, 2, and 4 passes using route B_C. The grain structure of the material was refined from 20.2 to 1.6 μm after 4 passes of ECAP at 200 °C. The 4 pass ECAPed alloy showed lower yield stress and higher ductility as compared to the as-extruded condition, indicating that texture softening has overcome the strengthening effects of grain refinement. The same trends in strength and ductility were also observed in shear punch testing. Similar shear strength and ductility values of the samples taken perpendicular to the extrusion direction (ED) and normal direction (ND) after 4 passes of ECAP indicated that {0 0 0 2} basal planes were inclined (∼45°) to the extrusion axis. The shear punch testing technique was found to be a useful method for verifying directional mechanical properties of the miniature samples of the ECAPed magnesium alloys.     

Effect of Sb addition on the tensile deformation behavior of lead-free Sn–3.5Ag solder alloy

Tensile deformation behavior of Sn–3.5Ag and Sn–3.5Ag–1.5Sb alloys was investigated at temperatures ranging from 298 to 400 K, and strain rates ranging from 5 × 10⁻⁴ to 1 × 10⁻² s⁻¹. After melting and casting, the samples were rolled to sheets, from which tensile specimens were punched and pulled to fracture in uniaxial tension tests. Scanning electron microscopy (SEM) was used to study the microstructure and fracture surface of the samples. Addition of 1.5% Sb into the binary alloy resulted in an increase in both ultimate tensile strength (UTS) and ductility. The enhanced strength was attributed to the solid solution hardening effects of Sb in the Sn matrix. The improved ductility was, however, caused by the structural refinement which results in the higher strain rate hardening of the Sb-containing alloy. This was manifested by the higher strain rate sensitivity (SRS) indices (m) of 0.14–0.27, as compared to 0.11–0.20 found for the Sn–3.5Ag alloy.     

Corrosion properties of a novel bulk Cu0.5NiAlCoCrFeSi glassy alloy in 288 °C high-purity water

Corrosion properties of a bulk Cu_0.5NiAlCoCrFeSi glassy alloy such as electrochemical corrosion potential (ECP), potentiodynamic polarization, and weight loss measurements were carried out for the first time in 288 °C high-purity (outlet conductivity < 0.07 μS cm^− 1) water. The change of ECP with dissolved oxygen (DO) showed a sigmoid curve. In addition, the Cu_0.5NiAlCoCrFeSi alloy exhibited a wide passive region and the passive current density was ∼ 2 × 10^− 4 A cm^− 2 in deaerated water containing 0.01 N sodium sulfate (Na₂SO₄) at 288 °C. A very low weight loss of ∼ 4.5 μg mm^− 1 was also found for the Cu_0.5NiAlCoCrFeSi alloy after immersion in deaerated 288 °C water for 12 weeks.     

Microstructure and enhanced mechanical properties of an Mg-10Gd-2Y-0.5Zr alloy processed by cyclic extrusion and compression

The evolution of microstructure and texture of an extruded GW102K Mg alloy processed by cyclic extrusion and compression (CEC) at 450 °C were investigated. Tensile tests were performed at room temperature and strain rate 5 × 10⁻³ s⁻¹. The results show that the microstructure was effectively refined, and the initial fiber texture became disintegrated and developed a new texture after 14 CEC passes. It was found that the strength and ductility were simultaneously increased compared with the as-extruded alloy. In particular, the elongation and yield strength were related in a line relationship having a positive slope. As the texture changed and texture intensity decreased, substantial grain refinement was observed. The hard second-phase particles were considered to be responsible for the uncommon properties of the GW102K alloy processed by CEC.     

Microstructure of superplastic QE22 and EZ33 magnesium alloys

Superplastic deformation has been observed in the QE22 and EZ33 magnesium alloys prepared by the special thermomechanical procedure. The microstructure was analysed by the scanning and transmission electron microscopes before and after deformation. Samples with the grain size of ∼ 1 μm were deformed at elevated temperature at the strain rates from 1 × 10^− 4 to 1 × 10^− 3 s^− 1. Microstructure analysis showed an existence of particles in the grain boundaries. This precipitates are very stable even at high temperature deformation. These heat resistant phases are very probably responsible for the grain stability and also prominent superplastic behaviour of alloys studied.     

Structural, electrical and optical properties of zirconium-doped zinc oxide films prepared by radio frequency magnetron sputtering

Transparent and conducting zirconium-doped zinc oxide films have been prepared by radio frequency magnetron sputtering at room temperature. The ZrO₂ content in the target is varied from 0 to 10 wt.%. The films are polycrystalline with a hexagonal structure and a preferred orientation along the c axis. As the ZrO₂ content increases, the crystallinity and conductivity of the film are initially improved and then both show deterioration. Zr atoms mainly substitute Zn atoms when the ZrO₂ content are 3 and 5 wt.%, but tend to cluster into grain boundaries at higher contents. The lowest resistivity achieved is 2.07 × 10^− 3 Ω cm with the ZrO₂ content of 5 wt.% with a Hall mobility of 16 cm² V^− 1 s^− 1 and a carrier concentration of 1.95 × 10²⁰ cm^− 3. All the films present a high transmittance of above 90% in the visible range. The optical band gap depends on the carrier concentration, and the value is larger at higher carrier concentration.     

Electrochemical preparation of Fe-Mn alloy film in organic bath

Fe-Mn alloy films have been prepared by electrodeposition in an organic bath containing FeCl₂ + MnCl₂ in dimethyl formamide. The electroreduction of Mn(II) was irreversible and the diffusion coefficient of Mn(II) was calculated to be 8.0 × 10^− 11 m² s^− 1 at 298 K. An amorphous film of Fe-Mn was obtained by potentiostatic electrolysis. The Mn content varied from 4.8 at.% to 72.3 at.% with increase in the applied cathodic potential. Scanning electron microscope investigation showed that the deposited film was homogeneous and consisted of spherical particles. Nano-sized pores were observed in the surface of these particles. After heat treatment at 773 K, large crystal grains formed and X-ray diffraction patterns indicate that solid solution of Mn in γ-Fe occurred. The alloying temperature of the Fe-Mn film was determined to be 1013 K using differential thermal analysis.     

Effect of temperature on deformation behavior and microstructures of TC11 titanium alloy

The isothermal compression deformation behavior of TC11 titanium alloy with beta microstructure was studied between 750 °C and 1100 °C under the strain rate ranging from 0.001 s⁻¹ to 10 s⁻¹ by THERMECMASTOR-Z simulator. In addition, the effect of temperature on microstructure was observed using optical microscope. The results showed that the temperature greatly affected the flow stress and microstructure of TC11 titanium alloy cooled from beta phase region in air. During hot deformation of TC11 titanium alloy, the steady state flow characteristic was observed at higher temperature or lower strain rate. In the α + β phase region, spheroidization fraction of α lamellar decreased with increasing temperature, while in near-β and β phase regions, dynamic recrystallization fraction increased with increasing temperature in all strain rates except at the strain rate of 0.001 s⁻¹.     

Influence of the supersaturated silicon solid solution concentration on the effectiveness of severe plastic deformation processing in Al-7 wt.% Si casting alloy

A comparative study of room temperature severe plastic deformation (SPD) of a hypoeutectic Al-7 wt.% Si casting alloy by high pressure torsion (HPT) and equal channel angular pressing (ECAP) has been performed. Microstructural parameters and microhardness were evaluated in the present work. Three different initial Si solid solution contents have been considered: as cast (C sample, 1.6 wt.% Si), annealed and quenched (Q sample, 1.2 wt.% Si) and annealed and furnace cooled (S sample, 0.7 wt.% Si). The samples processed by ECAP have smaller average Si particle sizes (0.9-1.7 μm), than those for samples processed by HPT (2.4-4.4 μm). The initial supersaturated Si solid solution is the major factor affecting the microstructure and the mechanical properties of the material. Fine deformation-induced Si precipitates from the supersaturated solid solution were responsible of the large grain refinement obtained by both SPD processing methods, which was considerably higher than that reported for pure aluminium. Q samples, processed by both SPD methods, containing an intermediate concentration of Si in solid solution, show the highest hardness due to the finest and most homogeneous microstructure. The finest and homogeneous grain size was ∼0.2 μm for the HPTed and ∼0.4 μm for the ECAPed Q samples.     

Transparent amorphous conductive Cd-In-Sb-O thin films for flexible devices

Transparent conductive amorphous Cd-In-Sb-O thin films were deposited on a flexible polyethylene naphthalate film by rf magnetron sputtering at room temperature. The large Hall mobility of ∼26 cm² V⁻¹ s⁻¹ was observed on the films with carrier density >10²⁰ cm⁻³. The carrier density varied from the order of 10²⁰ to 10¹⁷ cm⁻³ with increasing the oxygen partial pressure. The Hall mobility reached up to ∼17 cm² V⁻¹ s⁻¹, even at carrier density of ∼10¹⁷ cm⁻³. Flexible transparent filed-effect transistor was also fabricated using the Cd-In-Sb-O thin films as a channel layer and the device performance was investigated. The device exhibited a field-effect mobility of ∼0.45 cm² V⁻¹ s⁻¹ and an on-off ratio of ∼10² at room temperature.     

Effect of base and oxygen partial pressures on the electrical and optical properties of indium molybdenum oxide thin films

Indium molybdenum oxide thin films were RF sputtered at room temperature on glass substrates with a reference base pressure of 7.5 × 10^− 4 Pa. The electrical and optical properties of the films were studied as a function of oxygen partial pressures (OPP) ranging from 1.5 × 10^− 3 Pa to 3.5 × 10^− 3 Pa. The obtained data show that the bulk resistivity of the films increased by about 4 orders of magnitude (from 7.9 × 10^− 3 to 7.6 × 10¹ Ω-cm) when the OPP increased from 1.5 × 10⁻³ to 3.5 × 10^− 3 Pa, and the carrier concentration decreased by about 4 orders (from 1.77 × 10²⁰ to 2.31 × 10¹⁶ cm^− 3). On the other hand, the average visible transmittance of 30.54% of the films (brown colour; OPP = 1.5 × 10^− 3 Pa) was increased with increasing OPP to a maximum of 80.47% (OPP = 3.5 × 10^− 3 Pa). The optical band gap calculated from the absorption edge of the transmittance spectra ranges from 3.77 to 3.88 eV. Further, the optical and electrical properties of the films differ from those deposited at similar conditions but with a base pressure lower than 7.5 × 10^− 4 Pa.     

Chemical diffusion coefficient of lithium ion in Li3V2(PO4)3 cathode material

The kinetic properties of monoclinic lithium vanadium phosphate were investigated by potential step chronoamperometry (PSCA) and electrochemical impedance spectroscopy (EIS) method. The PSCA results show that there exists a linear relationship between the current and the square root of the time. The D?_Li values of lithium ion in Li_3-xV₂(PO₄)₃ under various initial potentials of 3.41, 3.67, 3.91 and 4.07 V (vs Li/Li⁺) obtained from PSCA are 1.26 × 10^− 9, 2.38 × 10^− 9, 2.27 × 10^− 9 and 2.22 × 10^− 9 cm²·s^− 1, respectively. Over the measuring temperature range 15-65 °C, the diffusion coefficient increased from 2.67 × 10^− 8 cm²·s^− 1 (at 15 °C) to 1.80 × 10^− 7 cm²·s^− 1 (at 65 °C) as the measuring temperature increased.     

Mobility of holes in a Si/Si0.8Ge0.2/Si metal oxide semiconductor field effect transistor

Using all standard scattering mechanisms the hole mobility in a metal oxide semiconductor field effect transistor SiGe conduction channel at 17 K and room temperature was calculated. The mobility measurements were performed at different bath temperatures in the range of 4-300 K. The 4 K peak mobility at a sheet carrier concentration, n_h, of 2.1 × 10¹¹ cm^− 2 is 5100 cm² V⁻¹ s^− 1 while the 300 K mobility has a peak value of 350 cm² V⁻¹ s^− 1. By comparing between theory and measurements it is shown that the interface impurities and surface roughness more strongly limit the mobility than alloy scattering does.