Electrocatalytic behaviour of titanium implanted with nickel and molybdenum ions

Abstract

The electrocatalytic activity of titanium induced by ion implantation has been investigated. Ion implantation was carried out using a metal vapour vacuum arc source ion implanter at room temperature. Nickel ion implantation was followed by molybdenum ion implantation at doses ranging from 1 × 10¹⁶ to 1 × 10¹⁷ ions/cm² at the same average extracting voltage of 45 kV. The concentration profiles of Ni and Mo ions in the near surface were detected by electron probe microanalysis and X-ray photoelectron spectroscopy. The catalytic behaviour of implanted titanium was determined by an electrochemical method. Potential versus current density curves for the cathodic hydrogen evolution reaction indicated that Ni and Mo ions implanted into titanium electrodes resulted in a low hydrogen overvoltage of 110-180 mV (at a current density of 200-400 mA cm^-2 in 30 wt-%KOH at 25°C) and excellent stability. The electrocatalytic activity induced by ion implantation can be explained provisionally by interactions between Ni and Mo ions and the titanium substrate.     

Microstructural and textural evolution during large strain hot rolling (LSR) of Mg–Al (AZ31) alloy

Abstract

Grain refinement has been achieved through large strain rolling (LSR) in Mg AZ31 alloy. The evolution of microstructure and texture has been found to be dependent on the amount of reduction. After the critical amount of reduction, grain refinement proceeds through continuous dynamic recrystallisation (CDRX).     

14—EQUIVALENT TWISTS IN TYRE CORDS

This paper describes an empirical method for choosing a twist level for a new tyre cord that will ‘match’ the twist in an existing successful cord, i.e., one that will give the same twist angle. The technique is based on published cord geometry and is shown to give reliable results. No knowledge of densities or packing factors is required, and the results are independent of the number of yarns in the cord. The method offers the possibility of calculating twist angles and related properties for cords at any twist once a sufficiently reliable value of one cord constant has been determined. A table of matched twists calculated in this way is given.     

Forming characteristics of coated products for packaging applications

Abstract

A comparison of forming characteristics has been conducted on two different thickness steel substrates used in the packaging industry. Three surface conditions were studied, namely, uncoated blackplate, a lacquered electrochromium coated steel (ECCS), and a typical film laminate specification. It was found that for identical forming conditions the failure rates of both blackplate and lacquered ECCS materials were higher than in the film laminated alternative. This is shown to be related to the frictional effects of the coatings. In the film laminate material, failures were only observed at high blankholder forces near the forming limit of the material. The blackplate material produced cups, which were 0·4 mm taller than both the lacquered and film laminated coatings.     

Numerical modelling for rotational moulding with non-isothermal heating

Abstract

In the rotational moulding process, the internal air temperature has been widely recognised as a tool to predict an optimum cycle time. This paper presents a new numerical approach to predict the internal air temperature in a two-dimensional (2-D) static model without requiring the consideration of the tumbling motion of polymer powder. The initial non-isothermal heating of the static model is actually formed by two changeable plastic beds (stagnant and mixing beds), which represent the actual stagnant and mixing pools inside a rotating mould respectively. In the numerical approach, the lumped-parameter system and coincident node technique are proposed to incorporate with the Galerkin Finite Element Method in order to account for the complex thermal interaction of the internal air. It helps to overcome the difficulty of multidimensional static models in predicting an accurate internal air temperature during the heating stage of rotationally powdery plastic. Importantly, the predicted temperature profiles of the internal air, oven times for different part thicknesses and process conditions accord with the available experimental results.     

Dissolution and precipitation kinetics of γ' in nickel base superalloy Udimet 520

Abstract

The influence of various solution andaging heat treatments on the dissolution and precipitation kinetics of γ' in wrought nickel base Udimet 520 superalloy was investigated, with the aim of determining optimum preforge and post-forge heat treatment schedules. Solution heat treatments at 1070, 1100, 1110, and 1120°C for 1, 2, and 4 h followed by water quenching were applied. Examination by SEM showed that in specimens solution treated at 1070°C the necklace type microstructure remained and partialagglomeration of γ' precipitates was observed even after 4 h holding. By contrast, after solutionising at 1100°C for 4 h, the γ' volume fraction decreased from 28 to 5% and when solution treated at 1140°C, abnormal grain growth was observed. The optimum solution treatment leading to an almost complete dissolution of γ' particles was determined to be 1120°C/4 h. Double aging treatments were carried out at 925°C/4 h/ AC (air cooled) followed by aging at 700 or 800°C for times ranging from 1 to 100 h. The results indicated that the precipitates have almost spherical shapes at the beginning and as the aging time is increased a partial change to a cuboidal shape is observed. This behaviour was more pronounced when aging at 800°C was employed. Microhardness measurements under both aging conditions showed that at 700°C hardness values increase about 60 HV when γ' particles grow 70 nm. On the other hand, in the samples aged at 800°C, hardness values increase with the particle size until a certain value and then drop. The precipitate growth process was followed by image analysis and the activation energy for γ' growth was evaluated to be 104 kJ mol ^-1. The results obtained are discussed in the framework of classic nucleation theory and compared with other workers' results.     

A Test for Liability to Electrostatic Charging—Reply

An investigation is described in which exhaustion exceeded 99.7 % when triphenyltin chloride was applied to wool in a hot dyebath. The associated residues were readily decomposed by persulphate, which indicated that it should be possible to mothproof wool with triphenyltin chloride without risk of contaminating the aquatic environment. Only small amounts of the triphenyltin were extracted from treated wool by human perspiration or saliva.     

Microstructural evolution of AZ61 magnesium alloy during hot deformation

Abstract

The microstructural evolution of AZ61 magnesium alloy during hot compression at various temperatures was investigated. The experimental results show that dynamic recrystallisation occurs over a wide temperature range. Grains can be greatly refined through dynamic recrystallisation. The mean size of the recrystallised grains increases with a decrease of temperature or value of Z (Zener – Hollomon parameter), while the reciprocal of the recrystallised grain size has a good linear relationship with the natural logarithm of the Z value, as well as the hyperbolic term of the flow stress. Basal and non-basal segments have been found in both recrystallised grains and primary grains, whereas dislocation pileups exist only in recrystallised grains when the temperature is lower than 673 K. The occurrence of twins is dependent on temperature and strain. When the strain increases, primary twins evolve into secondary twins. However, secondary twins grow with an increase of temperature; some secondary twins evolve into subgrains.     

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.     

Variation in as cast and aged structures of centrifugally cast heat resistant steel solidified in an electromagnetic field and under different cooling conditions

Abstract

The influences of an applied electromagnetic field and cooling conditions on the as cast and aged structures of centrifugally cast heat resistant HK40 steel tubes were investigated. The results reveal that both the electromagnetic field and the cooling ability of the casting mould have significant effects on the macrostructure morphology and the volume fraction and distribution of eutectic carbides, as well as on the homogeneity of secondary precipitation caused by high temperature aging treatment. The differences in the structures are attributed to the different solidification processes of the cast tubes. It is indicated that a reasonable combination of electromagnetic field and cooling conditions during solidification is greatly beneficial, leading to an improvement of creep resistance of cast tubes.