Crystallization Process of Iron-, Nickel-, and Cobalt-Based Amorphous Alloys Containing Silicon and Boron (Metallurgy)

Structural changes during heating or aging in a wide temperature range were exmained with three amorphous alloys of Fe_Si_B_, Ni_S_8B_ and Co_Si_B_ by measurements of electrical resistance, differential scanning calorie and Vickers hardness and also by transmission electron microscopy and X-ray diffraction. The results obtained are summarized as follows : (1) The crystallization process of three amorphous alloys is divided into four stages : (a) the incipient stage of crystallization where a certain short range ordering of atoms occurs, (b) the formation of primary metastable phases (MS-I), (c) the formation of secondary metastable phase (MS-II) with complex single structures, and (d) the formation of a stable phase consisting of a mixture of each equilibrium phase. The MS-I phase appears in the amorphous matrix in a manner of homogeneous nucleation and gradual growth, while the MS-II phase grows rapidly from a few nuclei and completely spreads over the amorphous matrix containing the MS-I phases. At higher temperatures, these MS-II phases transform finally to stable phases. (2) The temperature-time-transformation diagrams of three alloys were constructed. In these diagrams, distinct differences in the transformation sequence and the mode are observable in the upper and lower ranges of the critical temperature (Tx\u27). Above this boundary, crystallization by way of nucleation and growth proceeds through two metastable phases and finally to a stable phase. Below that temperature, on the other hand, progressive aging gradually changes the amorphous structure to the assembly of fine grains (about 100～200A) with a simple structure such as bcc, fcc, or hcp

Viscoelastic Behavior of Amorphous Metals

The viscoelastic behavior and its rate controlling process of amorphous metals have been examined by extensive experiments of tensile creep and stress relaxation using amorphous Pd-Si, Fe-P-C and Cu-Zr alloys. The differences in creep properties of amorphous and crystalline metals have also been discussed. Creep curves of all amorphous metals used may be classified into three stages of transient creep, steady-state creep and tertiary creep. The creep strain is composed of recoverable and irrecoverable components and it can be described in terms of viscoelastic elements in rheology. The steady-state creep is controlled by thermally activated process, and seems to be closely related with atomic diffusion in amorphous structure

Effects of Plasma Radiation on the Thomson Scattering Diagnostic Installed on the Large Helical Device

Recently we modified the Thomson scattering diagnostic (TS) installed on LHD so that DC levels (VDC) of all avalanche photodiodes (APD) used for detecting scattered light can be registered every 1 ms, which enabling us to make validity check on TS data taken under very intense plasma radiation. In the line of this task, we first examined how the pulse-performance of an APD degrades as the intensity of continuous light (JDC) incident to the APD increases. We found two effects are involved in deteriorating the pulse-performance of the APD: (1) the responsivity of the APD to a pulsed light drops as JDC increases, causing a systematic errors on the deduced electron temperature (Te) and density (ne); (2) the frequency response of the APD and the following circuit drops as JDC increases, which deforms the pulse shape. The bias voltage applied to the APD (Vb) has large influence on these behaviors, showing the best overall performance for a high JDC around Vb ? 0.5Vr, where Vr is the recommended voltage giving responsivity of 675 kV/W at 1060 nm. Considering these effects together, we set a conservative validity criterion for the pulse APD performance in term of the VDC: VDC < 0.5 V. The Vb = 0.5 Vr setup gives much reliable Te-profiles without a collapse in Te-profile for a much wider range of plasma radiation intensity. With this criterion, we check the validity of Te- and ne-profiles of two example data

Raman and Rayleigh Calibrations of the LHD YAG Thomson Scattering

We have carried out absolute calibrations of the LHD YAG Thomson scattering system by using Raman scattering and Rayleigh scattering in order to verify the applicability of Rayleigh calibration in the LHD Thomson scattering, and make a comparative study of Raman and Rayleigh calibrations. In the LHD Thomson scattering device, Rayleigh calibration is expected to give more reliable calibration factors. For the Rayleigh calibration, additional Rayleigh channel was installed into 20 polychromators. The other 124 polychromators without Rayleigh channel were calibrated by only Raman scattering. In the Raman calibration, pure gaseous nitrogen was introduced into the LHD vacuum vessel whereas the Rayleigh calibration was made by using air as target gas. The calibration factors obtained from the Raman and Rayleigh calibrations show good agreements. Uncertainties in the calibration factors obtained from the Raman and Rayleigh calibrations are discussed

Spontaneous Oxidization of an Amorphous Zr_<70>Au_<30> Alloy in Air

An amorphous Zr_Au_ alloy prepared by the melt-quenching technique was found to possess an extremely high oxidization tendency in air even at room temperature, even though the other Zr-based amorphous alloys remain unchanged in the same environment. Upon oxidization, the amorphous structure changes into a duplex crystalline structure consisting of a monoclinic ZrO_2 matrix including fcc Au particles with a size as fine as about 2 nm at an inter-particle spacing of about 4 nm. The oxidization tendency depends strongly on the humidity in air and becomes remarkable with increasing humidity. Furthermore, the oxidization causes a spontaneous pulverization of the ribbon into fine powders consisting of ZrO_2 and Au. The reason for the exceptionally high oxidization only for the Zr_Au amorphous alloy was inferred to be due to a combination effect of a weak attractive bonding nature between Zr and Au and a great catalytic ability of Au

Spontaneous Facial Mimicry Is Enhanced by the Goal of Inferring Emotional States: Evidence for Moderation of Automatic Mimicry by Higher Cognitive Processes

A number of studies have shown that individuals often spontaneously mimic the facial expressions of others, a tendency known as facial mimicry. This tendency has generally been considered a reflex-like automatic response, but several recent studies have shown that the degree of mimicry may be moderated by contextual information. However, the cognitive and motivational factors underlying the contextual moderation of facial mimicry require further empirical investigation. In this study, we present evidence that the degree to which participants spontaneously mimic a target\u27s facial expressions depends on whether participants are motivated to infer the target\u27s emotional state. In the first study we show that facial mimicry, assessed by facial electromyography, occurs more frequently when participants are specifically instructed to infer a target\u27s emotional state than when given no instruction. In the second study, we replicate this effect using the Facial Action Coding System to show that participants are more likely to mimic facial expressions of emotion when they are asked to infer the target\u27s emotional state, rather than make inferences about a physical trait unrelated to emotion. These results provide convergent evidence that the explicit goal of understanding a target\u27s emotional state affects the degree of facial mimicry shown by the perceiver, suggesting moderation of reflex-like motor activities by higher cognitive processes

Electrical Resistivity and Its Temperature Dependence of Al-base Quasicrystalline and Crystalline Alloys

Al-Mn and Al-Cr quasicrystalline and Al-Mn crystalline alloys were prepared by melt-quenching and their electrical resistivities were studied. The quenched samples exhibited an extremely high resistivity because of nonperiodic potential scattering and resonance scattering of the Fermi electrons. The temperature dependence of electrical resistivity of Al-22.5%Mn quasicrystalline was tried to fit by several models, and it was found that the plots of lnT (from 4.2 to 20 K) and T^2 (from 20 to 60 K) showed a straight line. The electrical resistivity of Al_6Mn crystalline alloy showed a linear temperature dependence over wide high temperatures, but that of Al_4Mn crystalline alloy showed a deviation from the linearlity. The values of P of the quasicrystalline alloys were larger than those of the crystalline counterparts