Interface microstructure of diffusion bonded austenitic stainless steel and medium carbon steel couple

Abstract

In the present study, an austenitic stainless steel and medium carbon steel were diffusion bonded. The effect of bonding temperature on microstructural changes and shear strength across the joint region was investigated by optical and scanning electron microscopy, energy dispersive spectroscopy and microhardness measurements. The results showed that the best joint free from microcrack and micovoids was obtained at 900°C with maximum shear strength of 475 MPa.     

Case hardening of zirconium

Abstract

The poor tribological properties of zirconium limit its application, particularly its use in valves in the nuclear industry. Following up on a successful program to case harden titanium, the authors applied the same techniques to zirconium. Although the two metals are closely related, the diffusing species used for titanium were not found to be suitable for zirconium because of cracking in the sub-ceramic diffusion zone. A modified approach using hydrogen to improve the ductility of the layer successfully reduced its hardness, but not its propensity to cracking.     

11—THE EFFECT OF BACKDRAFT APPLIED AT THE FIRST GILLING OPERATION AFTER WORSTED CARDING

The application of backdraft at the first gilling operation after carding results in significant reduction in percentage noil and an increase in the mean fibre length of the top. These effects depend on the backdraft and direction of feed. Percentage noil is also dependent on backratch but is independent of the faller-bar pinning density. Measurements are also given to show how back-roller force is affected by backdraft, backratch, and the total free space between the pins and the fallers.     

Effect of microstructure on attenuation mechanism of ultrasonic waves in carbon steels

Abstract

In this paper, fundamental concepts of ultrasonics and characteristics of distinctive microstructures have been used to simply explain the effect of microstructure on the attenuation mechanism of ultrasonic waves in carbon steels. In addition, it has been shown that application of the second medium hardness instead of the bulk hardness is more appropriate to correlate the sound velocity and the microstructure.     

Etching technique for revelation of plastic deformation zone in low carbon steel

Abstract

In this study, an etching technique to detect the localised plastic deformation behaviour in a low carbon steel was developed. With this technique, etching with Fry solution under ultrasonic vibration was carried out on samples plastically deformed and then heated at 550°C for a certain period of time. The plastic zone was revealed by different degrees of etching in the plastically deformed and non-deformed regions; the plastic zone was found to be only slightly etched, whereas the other region was deeply etched. From the surface offset after etching, the deformation zone was found to be observable even at low magnification, such as 10 times. As the heating duration increased, the plastic zone became clearer. The mechanism for such an etching reaction is discussed on the basis of electrochemical analysis.     

MicroRaman spectroscopy of protective coatings deposited onto C/C–SiC composites

Abstract

MicroRaman spectroscopy has been used in the present work to investigate the structure and composition of pyrolytic carbon (PyC) and SiC protective coatings formed under various chemical vapour deposition conditions. Analysis of spectra obtained during Raman line mapping experiments on samples with graded Si_xC_y layer in the region of about 700–1000 cm^?1 allows information to be extracted on different SiC polytypes. It was found that the graded SiC layered sample contained a mixture of 3C–SiC and 6H–SiC polytypes at the film/substrate interface, but for the major part of this layer the 3C–SiC (β-SiC) phase predominates. For pure PyC films, it was found that the formation of PyC layer begins at 1200°C and the layer formed at this temperature is more uniform with slightly larger crystallite size (～3 nm) compared to that in the layer formed at 1300°C.     

Recrystallisation textures in cold rolled low carbon steel containing ferritic and bainitic microstructures

Abstract

Low carbon steel strip was heat treated to generate four different starting microstructures (fine and coarse polygonal ferrite, acicular ferrite and bainite) for investigating their influence on texture development during cold rolling and annealing. The starting materials were cold rolled to 50–90% reduction and annealed for various times in the temperature range 853–953 K. The resultant microstructures and textures were examined mainly by electron backscatter diffraction and X-ray diffraction. The initial microstructure strongly influenced the crystallographic rotation paths during cold rolling, whereby high strain deformation generated strong {223}〈110〉 texture components in the polygonal ferritic microstructures, whereas a strong {001}〈110〉 texture was produced in the acicular/bainitic microstructures. Subsequent annealing generated, to varying degrees, the classic {111}〈uvw〉 (γ-fibre) recrystallisation texture in all materials. Unexpectedly, coarse polygonal ferrite produced the strongest γ-fibre recrystallisation texture after 70–90% cold rolling reduction. Based on arguments involving the effect of carbon in solution, initial grain size and deformation textures on recrystallisation texture development, it was shown that a strong γ-fibre texture can indeed be generated in coarse polygonal ferrite.     

An Ammonium Argentothiosulphate Bromide

A sparingly-soluble ammonium argentothiosulphate bromide salt (called B-salt) has been prepared by the addition of excess silver bromide to an ammonium thiosulphate solution over the concentration range 0·5 M to 2·5 M. Its nearest “simple” empirical formula is (NH₄)₄(AgS₂O₃)₃Br. Chemical and physical properties of the salt are described. B-salt is formed in the practical fixing bath and in the photographic emulsion. The fixation of a bromo-iodide emulsion yields a B-salt containing a small quantity of iodide.     

Microstructure in adiabatic shear bands in a pearlitic ultrahigh carbon steel

Abstract

Adiabatic shear bands, obtained in compression deformation at a strain rate of 4000 s^?1, in a pearlitic 1·3%C steel, were investigated. Shear bands initiated at 55% compression deformation with the width of the band equal to 14 μm. Nano-indentor hardness of the shear band was 11·5 GPa in contrast to the initial matrix hardness of 3·5 GPa. The high strength of the shear band is attributed to its creation from two sequential events. First, large strain deformation, at a high strain rate, accompanied by adiabatic heating, led to phase transformation to austenite. Second, retransformation upon rapid cooling occurred by a divorced eutectoid transformation (DET). The result is a predicted microstructure consisting of nano size carbide particles within a matrix of fine ferrite grains. It is proposed that the DET occurs in iron–carbon steels during high rate deformation in ball milling, ball drop tests and in commercial wire drawing.     

Surface oxidation of carbon fibre on tribological properties of PEEK composites

Abstract

In this work, ozone modification method and air oxidation were used for the surface treatment of polyacrylonitrile (PAN) based carbon fibre. The surface characteristics of carbon fibres were characterised by X-ray photoelectron spectroscopy. The interfacial properties of carbon fibre reinforced PEEK (CF/PEEK) composites were investigated by means of the single fibre pull-out tests. As a result, it was found that IFSS values of the composites with ozone treated carbon fibre are increased by 60% compared with that without treatment. X-ray photoelectron spectroscopy results show that ozone treatment increases the amount of carboxyl groups on carbon fibre surface, thus the interfacial adhesion between carbon fibre and PEEK matrix is effectively promoted. The effect of surface treatment of carbon fibres on the tribological properties of CF/PEEK composites was comparatively investigated. Experimental results revealed that surface treatment can effectively improve the interfacial adhesion between carbon fibre and PEEK matrix. Thus the wear resistance was significantly improved.