Investigation of Precipitation Behavior in Age-Hardenable Cu-Ti Alloys by an Extraction-Based Approach

We investigated the precipitation processes in Cu-4 mol pct Ti alloy specimens aged at 723 K (450 °C), by means of X-ray diffraction and chemical analyses of the precipitates extracted from the parent alloy specimens. Aging-induced precipitate particles of a spinodally decomposed disorder, α′; those of a metastable order, β′-Cu₄Ti; and those of a stable order, β-Cu₄Ti, were continuously formed in the aged specimens. The extraction of the precipitate particles from the aged specimens by submergence in a nitric solution allowed for not only the structural analyses of the constituent precipitate phases but also the quantitative evaluation of their chemical compositions and volume fractions. Early during the aging process, the supersaturated Cu solid solution decomposes spinodally in a continuous manner, and an unstable disorder, α′, appears. Then, fine needle-shaped β′-Cu₄Ti particles, which have a Ti content of approximately 37.5 mol pct, form in the Cu matrix. During prolonged aging, coarse cellular components composed of the terminal Cu solid solution and stable β-Cu₄Ti particles which have a Ti content of 20.5 mol pct nucleate and grow, primarily in the grain boundaries, at the expense of the metastable β′-Cu₄Ti particles. The volume fraction of the β′-Cu₄Ti particles in the alloy reaches a maximum of approximately 1.7 pct after aging for 24 hours, while that of the β-Cu₄Ti particles increases steadily to more than 18 pct after 480 hours. The volume fraction of the fine β′-Cu₄Ti particles in the alloy specimens remained constant throughout the age-hardening, indicating that the hardening is primarily owing to the fine dispersion of the β′-Cu₄Ti particles and not because of the large volume fraction of coarse β-Cu₄Ti particles.     

High temperature stable GHz-range low-loss wide band transducersand filter using SiO2/LiNbO3, LiTaO3

GHz-range low-loss transducers and filters are required for communication systems, especially mobile telephone communication systems. Many types of low insertion-loss transducers and filters utilizing the high electromechanical coupling coefficient (K²) materials such as LiNbO₃ and LiTaO₃ have been developed. Unfortunately, these materials have large temperature coefficients of the frequency (TCF). In this paper, SAW substrates with high coupling coefficients and low propagation attenuations and small temperature coefficient of frequency in the GHz-range are theoretically and experimentally investigated. The experimental results show very low propagation loss of 0.02 dB/λ ₀ and larger K² than those of the substrates of LiNbO₃ and LiTaO₃ at the TCF of below -5 ppm/°C at 1~2 GHz-range. The low-loss filter results using internal reflection types of IDT show the insertion loss of about 2.9 dB at 1 GHz and 4.9 dB at 2 GHz under the TCF's of 0 and +20 ppm/°C. These materials are applicable for devices at GHz-range because SiO₂ thickness is very thin such as below 1 μm and the center frequency shift of the filter versus SiO₂ thickness is very small     

Slip mechanism in optical fiber coating with open-cup applicators

The allowable maximum coating speed of optical fibers has been correlated to the flow properties of the coating material itself. The maximum smooth coating speed has been measured from the coating thickness fluctuation-coating speed curves using several types of silicone resins. Flow curves of the silicone resins also have been measured by two different viscometers, i.e., cone-plate and capillary viscometers. The maximum smooth coating speed, at which the coating thickness fluctuation begins to increase, has been found to correspond to the critical shear rate at which the flow curve deviates from a power law. This correspondence probably results from the fact that the slip occurs both at the fiber-coating material interface and at the viscometer (cone, plate, or capillary)-coating material interface. Accordingly, the maximum smooth coating speed can be predicted from the critical shear rate value without the actual fiber coating experiments.     

Effects of chromate treatments on environmental stability of lead/tin alloy joints bonded with an ethylene–acrylic acid copolymer. II. Failure mechanism in distilled water

The environmental stability in distilled water and the failure mechanism of cathodically chromated tin, lead, and lead/tin alloy joints bonded with an ethylene–acrylic acid copolymer have been investigated by T-peel tests and ESCA and SEM analyses of the fractured surfaces. The peel strength of chromated lead/tin alloy joints and of both untreated and chromated tin joints is kept unchanged with water immersion, whereas that of untreated lead/tin alloy joints and of both untreated and chromated lead joints decreases rapidly with water immersion. ESCA and SEM observations show that lead/tin alloy surfaces consist of both lead and tin phases and that the tin phase interface deteriorates gradually with water immersion after premature deterioration of the lead phase interface. The stabilization effect of chromate treatments for lead/tin alloy joints is due to retardation of the underfilm corrosion of the tin phase.     

Rapid and Simple Identification of Free Magnesia in Steelmaking Slag Used for Road Construction Using Cathodoluminescence

Metallurgical and Materials Transactions B - Reuse of steelmaking slags is important for the effective use of natural resources. Free magnesia (f-MgO) in steelmaking slag may cause serious problems...     

A new leaky NRD guide based on a grating structure

Analysis and experiment of a new leaky nrd guide based on a grating structure is described. Analysis employs a mode coupling procedure which yields highly accurate results while presenting the advantage of simplicity and ease of manipulation. Numerical values for the phase and leakage constants are presented and the role of each grating parameter is assessed. Theoretical results are compared with experimental data for different geometric and constitutive parameters and reasonable agreement between them is obtained.     

Thin film-coated waveguide CO2laser

A new type of radio frequency (RF) excited waveguide laser with a rectangular cross section is proposed which is composed of two dielectric or lossy materials and two metallic electrodes which are coated by a thin film with small absorptions. Theoretical and experimental analyses show that the maximum output powers of the new waveguide laser are much larger than those of conventional ones.     

Positive/negative reflection-type SAW reflectors on ST-quartz using new fabrication technique

A positive/negative reflection-type (PNR) SAW grating reflector on an ST-quartz substrate utilising both a gold and aluminium strip and its simple fabrication technique requiring no critical mask alignment are described.