Flow analysis of semi solid processing for grey cast iron

Abstract

Fluidity tests for semi solid processed grey cast iron were conducted at different degrees of primary fraction solid using fluidity strips with 2·5, 5 and 14 mm wall thickness. The microstructure of the fluidity strip castings was examined. Fluidity parameters, such as slurry velocity, critical solid concentration and choking range were studied. It can be concluded that critical solid concentration increases with the increase of wall thickness. The slurry velocity drops suddenly at a certain fraction solid very near to the critical solid concentration. Choking range zone can be measured by observing microstructure. A solidification model for fluidity has been developed based on the literature and microstructure study of semi solid processed grey cast iron. A mathematical equation has been obtained from the solidification model by modifying Flemings' fluidity model in order to analyse cavity filling of semi solid grey cast iron.     

Multilayer Metal Film Plating on Glass

It has been shown that an under-layer of SiO₂ · nH₂O on a silicate glass surface, promotes the adsorption of Sn(II) hydroxycompounds, resulting in the formation of Sn–O–Si chemical bonds. It also: contributes to the formation of monodispersed Sn(II) compound nanoparticles; levels the glass surface micro-relief; ensures the deposition of fine-grained metal films; increases the rate of Ni–P and Cu electroless plating; and increases the rate of the adhesion interaction between the surface of the silicate glass and metal films. It opens up the possibility of electroless and electrochemical plating of 5–10 μm thick multilayer metal and alloy films.     

Surface Modification of Polymer Films for Improved Adhesion of Deposited Metal Layers

Plasma treatment and vacuum Al deposition on films from biaxially oriented polypropylene is a multistep large scale industrial process, mainly ending up in packaging film laminates. As atmospheric plasma treatment processes suffer from lack of reproducibility, low pressure plasma treatment processes that can be operated in-line with the metal deposition are being developed. Process development is difficult, because the final packaging film laminate has to deliver optimum properties of adhesion as well as of the barrier against oxygen and water vapor permeation. As a typical production run involves tens of thousands to up to one hundred thousand square meters of film, experiments on an industrial scale are expensive, so smaller scale experimental processes are needed, which so far do not match well enough with industrial process characteristics. Moreover, bonding mechanisms between the treated substrate film and the deposited Al layer are not sufficiently understood. This paper describes the sequence in development and optimization of substrate films and plasma treatment that has been performed on an experimental as well as on an industrial scale. A sufficient correlation between experimental and industrial scales was achieved, which helps to perform development and optimization on a small scale before scaling up to industrial processes. However, improvement is still needed both in fundamental understanding of the aluminum–polypropylene interface as well as in experimental equipment and methodology.     

Effective conductivity measurements of silver coatings employing sapphire dielectric resonator technique

Abstract

A dielectric resonator method of measuring electrical sheet conductivity of electrolytic silver coatings is presented. The method is compared with standard methods normally used for conductivity characterisations of metal coatings. Three types of electrolytes to deposit silver layers have been used and sheet conductivity was measured for each type of coating. The results revealed different values for different types of coatings. The dielectric resonator method seems to be very useful for electrolytic metal coating characterisations.     

Prediction of steady state dilution in multipass hardfacing overlays deposited by self shielded flux cored arc welding

Abstract

A method of predicting the steady state dilution of multipass hardfacing overlays deposited via self shielded flux cored arc welding is described. A new variable is defined and used to describe the steady state dilution of multipass overlays. A mathematical model for dilution is presented in terms of this variable. Eight multipass overlays were deposited, using different combinations of welding parameters in each instance. The steady state dilutions for these overlays were measured and compared with those predicted by the model for dilution. It is found that, with an empirical correction, it is possible to predict the dilution of multipass hardfacing overlays over a wide range of welding conditions. This predictive capability establishes a relationship between welding process variables and the steady state composition, and hence the microstructure, of high chromium white iron weld overlays. Microstructure–wear relationships can then be applied to complete the link between welding parameters and the wear performance of the overlay.     

Integrated Design of an Ionic Polymer–Metal Composite Actuator/Sensor

We are studying the robotic application of ionic polymer–metal composite (IPMC). The characteristics of IPMC greatly depend on the type of counterions, and it is considered that the performance of the actuators can be improved by combining the actuators with several types of counterions and applying an integrated control. IPMC also has a sensor function, as the IPMC film generates an electromotive force when it is deformed. It has the possibility to be integrated into an IPMC actuator with soft actuation. In this paper, we consider an integrated design of an IPMC actuator/sensor, and investigate control of the combined IPMC actuators using H _∞ control and the construction of an IPMC sensor system.     

Experimental determination of time taken for openly exposed metal surfaces to dry

Abstract

The time taken for wetness sensors on zinc plates, openly exposed to the atmosphere, to dry was analysed at four sites in southern Australia. The sites cover a range of environmental conditions from inland to marine. A number of typical drying patterns were observed, and it was found that these patterns could be related to the environmental severity and the probable presence of various salt contaminants. Therefore, at the marine site drying was frequently slow (>4 h) and appeared to be controlled by the presence of salts with a low deliquescent relative humidity (DRH) such as MgCl₂. In contrast, at the inland sites drying was generally more rapid, which was consistent with either the drying of a clean surface or that of a surface controlled with salts of high DRH such as NaCl. The present paper presents histograms of drying rate for each site and the relationship between the distributions in drying rate and the environmental conditions is discussed. The relevance of the present study to modelling of atmospheric corrosion and to the design of cyclic tests to duplicate atmospheric corrosion is also discussed.     

Highly porous metals and ceramics

Abstract

Cellular solids are a class of highly porous materials that covers a wide range of structures, such as foamed materials, replicated porous or additive manufactured structures, honeycombs, lattice structures, interconnected fibres or hollow spheres and syntactic foams. The pores can be more or less closed or completely open. Depending on their morphology and composition, these materials possess unique properties and are used as components in special and advanced engineering applications. These include filtering liquids and particles in gas streams, porous burners, biomedical devices, lightweight stiff structures, impact absorbers, sound damping modules, thermal management components, etc. The present paper gives an overview on the main fabrication methods and the resulting architectures, in relation to applications of metals and ceramics with >50 vol.-% porosity.     

Aluminium powder particles produced by SAMD technique: typical characteristics and correlations between processing conditions and powder size

Abstract

The present paper consists of two parts. In the first part the principles of a new method of metal powder production, termed 'solid assisted melt disintegration (SAMD)' are discussed and the typical characteristics of the produced powder are outlined. In the second part the effects of some processing parameters on the size distribution and mean diameter of the powder are reported. The SAMD method involves mixing solid particles (i.e. alumina) with the liquid aluminium alloy aided by mechanical agitation. The shear force induced by the impeller is transferred to the metal via the non-wetting solid medium and results in melt disintegration. The resulting mixture of aluminium droplets and alumina particles are subsequently cooled in air and screened through 300 μm sieve to separate alumina from solidified aluminium powder particles. The SAMD technique has demonstrated the capability to produce a wide particle size distribution. The small sized particles (i.e. <53 μm) exhibited irregular shapes, but larger ones were mostly spherical. These powder particles were dense (pore free) without attached satellite particles and exhibited a relatively coarse microstructure. The processing parameters investigated include the size of Al₂O₃ particles, Al₂O₃/Al weight ratio, stirring speed and stirring time. It was concluded that there exists an optimum value for each of the aforementioned parameters corresponding to a minimum in the mean particle size.