Hot Spinning Research Articles

Ti-6Al-4V 합금의 열간 전단 스피닝

A method for estimating the shear spinnability is suggested, and it was applied to sheets of Ti-6Al-4V alloy for estimation of shear spinnability at hot working temperature. The effective working temperature was <TEX>$850^{\circ}C$</TEX> or above. The hot spinning operation was carried out in two steps of shear spinning. The reduction of thickness at the first step was 50% and 45% at the second, and the overall reduction of thickness was 72.4%. The cone spinning process could produce a uniform wall thickness with only a few percent tolerance, proving itself appropriate for making cones of Ti-6Al-4V alloy with uniform wall thickness.

Study on Microstructure Evolution of TA1 during Plane Compression and its Similarity to Power Spinning

The hot power spinning process of TA1 has been studied on the base of isothermal plane compression model in this paper. The microstructures of spun workpieces and plane compression specimens are analyzed and the microstructure evolution mechanism has been investigated. The results reveal that the microstructure evolution has similar mechanism between power spinning and plane compression. Plane strain compression can be used to predict and control the microstructure of as-spun TA1 workpiece.

Ultrafast Transport of Laser-Excited Spin-Polarized Carriers inAu/Fe/MgO(001)

Hot carrier-induced spin dynamics is analyzed in epitaxial Au/Fe/MgO(001) by a time domain approach. We excite a spin current pulse in Fe by 35 fs laser pulses. The transient spin polarization, which is probed at the Au surface by optical second harmonic generation, changes its sign after a few hundred femtoseconds. This is explained by a competition of ballistic and diffusive propagation considering energy-dependent hot carrier relaxation rates. In addition, we observe the decay of the spin polarization within 1 ps, which is associated with the hot carrier spin relaxation time in Au.

Microstructure evolution of TA15 titanium alloy during hot power spinning

The microstructure evolution of TA15 titanium alloy during hot power spinning was studied. Effects of wall reduction on microstructure evolution of TA15 titanium alloy were researched. Slip deformation is the main deformation mechanism accompanying with twinning to coordinate the deformation. The microstructure gradually transforms into fine fibrous microstructure and the aspect ratio of primary α grain increases with increasing wall reduction. The recrystallization fraction and microhardness increase with increasing reduction.

Effect of oxides on the reaction kinetics during hot-dip galvanizing of high strength steels

Selective oxidation of the minor alloying elements during annealing prior to hot-dip galvanizing cause poor wetting with liquid zinc, resulting in bare spot defects. The effect of surface coverage, morphology (i.e., size and distribution) of the oxides on the reaction kinetics was examined. The Zn wettability has been determined by sessile drop contact angle measurement method and the Fe–Al interfacial layer was investigated by the use of a novel hot temperature spinning process. It has been found that besides the overall surface oxide coverage, size of the oxide islands is a dominant factor in affecting the reaction kinetics.

Study on forming condition and tool of flywheel by using flow forming process

Many plastic forming methods, such as cold and hot forging, hydroforming, deep drawing, extrusion, rolling and spinning have been researched to develop metal plastic forming techniques. Still, no appropriate tool exists for the process and for the required geometry in manufacturing, especially in the forming fields. Thus, through this study we examined exhaustively flow forming and an appropriate material for extreme plastic deformation and flow stress. To this end, we focused on volume increase per unit length against the spinning process, a flow forming method, where the most important consideration is probably to sustain the metal flow as well as to prevent metal fold in the forming process. We chose a gear part of the flywheel of an automotive engine for the study model which consists of a separate plate and gear with different thicknesses, welded for assembling two parts. The rim of the squared section, thickened for gear machining on the plate edge, was manufactured through the flow forming method. Because this method does not allow the required geometry when forming, incremental forming was applied for flow forming. In addition, the geometry and process conditions of the forming tool based on the forming features were investigated in each step. As results of the present study, the optimised forming conditions for gear machining considering the thickness of the outer edge of the flywheel were evaluated using comparable tests, with various groove depths, angles and process conditions in each step of the manufacture of the forming roller.

Some advances in local loading precision forming of large scale integral complex components of titanium alloys

The large scale integral complex components of titanium alloys have been attracting increasing applications in the aerospace industry because they can meet the requirements of high performance, lightweight and high reliability. The local loading method which can control unequal deformation is an essential way to form such components. There are key problems to be solved urgently in the research and development of local loading method, and finite element numerical simulation in combination with theoretical analysis and experimental investigations has been playing a more and more important role in this field. This paper presents the state of the art of some local loading forming technologies and their applications in manufacturing titanium components, including the isothermal local loading forming of large scale integral rib web components, hot rolling of large seamless rings and hot spinning of thin walled shells.

Coupled thermo-mechanical FE simulation of the hot splitting spinning process of magnesium alloy AZ31

Abstract Magnesium alloy AZ31 shows excellent ductility and formability at elevated temperatures, and using hot splitting spinning it can be formed into a structural component subjected to impact loadings, such as, a wheel hub of aero undercarriage or kinds of light whole wheels. In this paper, based on the analysis of microstructures and deformation characteristics of magnesium alloy AZ31, a reasonable deformation temperature range is obtained during the thermoplastic forming process. Adopting a flow stress model of magnesium alloy AZ31 considering the dynamic recrystallization (DRX), a 3D elastic–plastic FE model of hot splitting spinning of magnesium alloy AZ31 is established based on the FEM software platform of ABAQUS/Explicit and a developed 3D-FE model of cold splitting spinning, and its reliability is validated. Furthermore, field distributions of deformed component, including temperature fields, stress fields and strain fields, and variations of different nodal temperatures are obtained. And the influencing laws of different initial temperatures of disk blank and different feed rates of splitting roller on forming quality of deformed flanges are investigated, consequently the optimal forming temperature is approximate 300 °C and the optimal feed rate of splitting roller ranges from 1 to 3 mm/s during the hot splitting spinning process of magnesium alloy AZ31. The results may help to understand the forming characteristics and optimum design of the hot splitting spinning process.

Para-sexiphenyl-CdSe/ZnS nanocrystal hybrid light emitting diodes

CdSe/ZnS core/shell nanocrystals (NCs) are integrated into para-sexiphenyl (p-6P) based hybrid light emitting diodes, to obtain green and red emission in addition to blue emission originated from p-6P. For the active region of the devices, ultrathin layers of p-6P and NCs are deposited by hot wall epitaxy and spin casting, respectively, resulting in current-voltage characteristics with small leakage currents and low onset voltages. The achieved electroluminescence exhibits narrow emission line widths and thus high color purity, as required for color display applications.

Hot shear spinning of cast aluminium alloy parts

A hot shear spinning process of cast aluminium alloy parts was developed to eliminate casting defects and to obtain a desired distribution of wall thickness. The forming load of the shear spinning is comparatively low even for large deformation requisite for eliminating the casting defects. Dendrites and shrinkage cavities in the cast aluminium alloys were successfully eliminated without occurrence of a fracture by the hot shear spinning. Surface cracks around the corner of the mandrel caused by large shear deformation were reduced by decreasing the feed rate of the roller and by increasing the tip radius of the roller. It was found that hot shear spinning is effective in improving the mechanical properties of cast aluminium alloys parts.

구조 효율을 고려한 CNG 자동차 연료저장용기의 최적설계

Type Ⅱ compressed natural gas(CNG) storage vessels for automobiles have been acknowledged for their excellence and have recently become established in local regions. Their supply is not only to automakers in Korea such as Hyundai Motors but they are being increasingly exported. Although the available products have undergone safety evaluations and are certified by an authorized institution they are still short of the optimal design that is possible for such storage vessels. This research investigates the shape and thickness of the dome with the aim of optimizing the type Ⅱ CNG storage vessels by using a finite element analysis technique. CNG storage vessels can be largely divided into 3 parts namely, the hear part, the cylinder part and the dome part. The head part is designed by means of a hot spinning process and this method is safer than that used in the design of the dome part even though its shape is similar. The thickness of the liners and reinforcing materials was optimized based on the requirements of the cylinder and dome parts. In addition, the shape of the dome, which is most suitable for Type Ⅱ CNG storage vessels, is proposed by a process of review and analysis of various existing shape, and then conducting a structural stability evaluation to ensure the optimal design plan.

Effect of spinning deformation on microstructure evolution and mechanical property of TA15 titanium alloy

Hot spinning of tubular workpiece of TA15 alloy was conducted on a CNC spinning machine, and the microstructure evolution during hot spinning and annealing was observed and mechanical properties of spun tubes were tested. The results show that with the increase of spinning pass, the fiber microstructure comes into being gradually in axial direction and the circumferential microstructure also stretches obviously along circumferential direction. At the same time, the tensile strength increases and elongation decreases not only in axial direction but also in circumferential direction. When the reduction ratio of wall thickness rises close to or over 40%, tensile strength increases and elongation decreases more rapidly, which means that tubular workpiece of titanium alloy can be strengthened bi-directionally by power spinning. The ductility of spun workpiece of TA15 alloy could be improved by annealing at the temperature no higher than recrystallization temperature with slight decrease of tensile strength.

Strongly bias-dependent spin injection from Fe inton-type GaAs

We report electrical spin injection into an $n$-doped GaAs $({N}_{d}=1\ifmmode\times\else\texttimes\fi{}{10}^{18}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3})$ region from an Fe thin film grown by molecular beam epitaxy. The spins are injected through an $n\text{\ensuremath{-}}{\mathrm{Al}}_{0.1}{\mathrm{Ga}}_{0.9}\mathrm{As}$ Schottky barrier on a spin light emitting diode. Spin injection is detected optically via carrier recombination in the layer immediately adjacent to the Schottky barrier, allowing the spin transport to be studied through this important region of interest. A pronounced dependence of injected spin polarization upon applied bias voltage reveals that efficient spin injection occurs across a range of $\ensuremath{\sim}1\phantom{\rule{0.3em}{0ex}}\mathrm{V}$, dropping off sharply to zero at all temperatures. At bias voltages higher than that at which the maximum spin injection occurs, the Schottky barrier resistance is lowered, accompanied by hot electron spin transport in the semiconductor.

Mechanical properties of Fe 3Al-based alloys with addition of carbon, niobium and titanium

Several Fe 3Al-based iron aluminides with the addition of alloying elements carbon, niobium and titanium were produced by vacuum induction melting (VIM) and hot spinning forging. Analytic techniques including transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used in studying the microstructure and fracture manner of these alloys. The results show that due to the addition of alloying elements, the superlattice dislocations tend towards multiple slipping, leaving behind on their slip plane ribbons of square-shaped slip-induced antiphase boundaries. The elongation of Fe 3Al in tension at room temperature increased to about 10% by the addition of suitable alloying elements, the usage of thermo-mechanical processing that has the function of refining grains and substructures, and subsequent annealing.

Guest Editor's Introduction: Special-Purpose Computing

My awareness of special-purpose computing goes back quite a long time. In the early 1980s, my former grad-school housemate and (still) good friend Doug Toussaint worked with Bob Pearson and John Richardson on a special-purpose computer to study the Ising model. They constructed and successfully used that computer, but by 1983, when Doug and I met up again at the University of Southern California, San Diego (UCSD), he was using the Ising model computer in his office as a coffeemaker stand, not for studying hot Ising spins. By serving as guest editor, I hoped to find a mix of mature and emerging projects that would provoke readers to wonder whether their own problems would be suited with a special-purpose computer.

Efficient electrical spin injection in GaAs: A comparison between AlOx and Schottky injectors

We demonstrate electrical spin injection in GaAs from ferromagnetic metals through tunneling. We use and compare an AlOx insulating layer as well as the native Schottky barrier at the metal–semiconductor interface as tunnel barriers. The injected spin polarization has been measured by analyzing the electroluminescence polarization using the oblique Hanle effect technique. The observed bias dependence of the measured spin polarization is sensitive to both the type of injector and the doping profile in the semiconductor. Hot electron spin relaxation due to the D’yakonov–Perel spin relaxation mechanism has been identified as the cause of the different bias dependence in two AlOx-based injectors with different doping levels of the active region while a change in the electron transit times in the highly doped interfacial region has been found as the cause of the bias dependence in the Schottky-based injectors.

Fabrication of fluoride glass planar waveguides by hot dip spin coating

A hot dip spin coating technique has been developed and applied to form fluoroaluminate glass waveguides with thickness ranging from 2 to 10 μm and waveguides losses of 0.1 dB/cm at 1048 nm.

Optically induced instability of spin precession in magnetic quantum wells

Dynamic phase separation in CdMnTe quantum wells under femtosecond pulse excitation leads to formation of hot and cold spin domains. Using Fourier spectroscopy of the time-resolved magneto-optical Kerr effect we determine the temperatures and the total areas of each kind of domain. The instability is shown to be triggered by the magnetic field above a threshold value.

Calculations of hot electron magnetotransport in a spin-valve transistor at finite temperatures

Hot electron magnetotransport in a spin-valve transistor has been theoretically explored at finite temperatures. We have calculated the parallel and anti-parallel collector current by changing the relative spin orientation of the ferromagnetic layers at finite temperatures. In this model, hot electron energy redistribution due to spatial inhomogeneity of Schottky barrier heights and hot electron spin polarization in the ferromagnetic layer at finite temperatures have been considered. The results of these model calculations agree with experimental data in a semi-quantitative manner. We therefore suggest that both these effects should be taken into account when one explores the hot electron magnetotransport in a spin-valve transistor at finite temperatures.

Bias voltage and temperature dependence of hot electron magnetotransport

We present a qualitative model study of energy and temperature dependence of hot electron magnetotransport. In this model calculation, the strong spin dependent inelastic scattering strength of hot electrons and spin mixing due to thermal spin waves have been taken into account. In addition, spatial inhomogeneity of Schottky barrier height has been considered. This calculations display that the magnetocurrent accords with the recent experimental data qualitatively at room temperature if we include the spin mixing effect with hot electron spin polarization although the experimental observation is not easy to interpret. Thus, if one measures the temperature dependence of magnetocurrent, then the mechanism suggested here will be tested whether it is acceptable.