Corrosion study of metallic biomaterials in simulated body fluid

Titanium alloys and stainless steel 316L are still the most widely used biomaterials for implants despite emerging new materials for this application. There is still someambiguity in corrosion behavior of metals in simulated body fluid (SBF). This paper aims at investigating the corrosion behavior of commercially pure titanium (CP-Ti), Ti–6Al–4V and 316LVM stainless steel (316LVM) in SBF (Hank’s solution) at37 ºC using the cyclic polarization test. Corrosion behavior was described in terms of breakdown potential, the potential and rate ofcorrosion, localized corrosion resistance, andbreakdown repassivation. The effects of anodizing on CP-Ti samples and the passivation on the 316LVM were studied in detail. It was shown that CP-Ti exhibited superior corrosion properties compared to Ti–6Al–4V and 316LVM.

The mutual effect of iron and manganese on microstructure and mechanical properties of aluminium –silicon alloy

The effect of iron and manganese concentration on the morphology of complex intermetallics and their influence on the mechanical properties and microstructure has been studied in an Al-16.67 wt. % Si alloy with three content of iron (0.4, 1.2, 1.8 wt.%), and two different content of manganese, i.e. 0.6 and 0.9 wt.%. The intermetallic compounds are formed at high iron contents or at high concentrations of manganese with low iron. The microstructural investigation by Clemex software showed that the biggest intermetallic size reached the surface area of 12750 μm2, when the amount of iron was increased from 1.2% to 1.8% wt.%. It was also showed that the volume fraction of intermetallic compounds increases as the iron and manganese content increases. Formation of complex intermetallic phases with iron adversely affects tensile strength decreasing from 229MPa with 0.4 wt.% of iron to 187MPa when iron content was increased to 1.8 wt.%.

Hydrometallurgical process for extraction of metals from electronic waste-part I: material characterization and process option selection

Used electronic equipment became one of the fastest growing waste streams in the world. In the past two decades recycling of printed circuit boards (PCBs) has been based on pyrometallurgy, highly polluting recycling technology which causes a variety of environmental problems. The most of the contemporary research activities on recovery of base and precious metals from waste PCBs are focused on hydrometallurgical techniques as more exact, predictable and easily controlled. In this paper mechanically pretrated PCBs are leached with nitric acid. Pouring density, percentage of magnetic fraction, particle size distribution, metal content and leachability are determined using optical microscopy, atomic absorption spectrometry (AAS), X-ray fluorescent spectrometry (XRF) and volumetric analysis. Three hydrometallurgical process options for recycling of copper and precious metals from waste PCBs are proposed and optimized: the use of selective leachants for recovery of high purity metals (fluoroboric acid, ammonia-ammonium salt solution), conventional leachants (sulphuric acid, chloride, cyanide) and eco-friendly leachants (formic acid, potassium persulphate). Results presented in this paper showed that size reduction process should include cutting instead of hammer shredding for obtaining suitable shape and granulation and that for further testing usage of particle size -3 +0.1mm is recommended. Also, Fe magnetic phase content could be reduced before hydro treatment.

An overview of R&D work in friction stir welding at SMU

Friction stir welding (FSW) is an innovative solid-state material joining method invented by The Welding Institute (TWI) in 1991 and has been one of the most significant joining technology developments in the last two decades. It has evolved into a process focused on joining arc weldable (5xxx and 6xxx) and unweldable (2xxx and 7xxx) aluminum alloys to a point where it can be implemented by the aerospace and automotive industries for their joining needs.Research towards the further extension of the process to join dissimilar metal combinations like Fe-Al and Al-Cu is currently underway. A few of the important advantages of FSW over conventional joining techniques include improved joint properties and performance, low-deformation of the workpieces, a significant reduction in production costs and the freeing of skilled labor for use in other tasks. Compared to the conventional arc-welding of aluminum alloys, FSW produces a smaller heat affected zone, and it also allows the successful joining of aluminum alloys, steel, titanium, and dissimilar alloys with a stronger joint.

Severe plastic deformation of metals

This paper provides an introduction in the field of severe plastic deformation (SPD). First of all the main methods to produce SPD materials are discussed. In the following section, the mechanisms leading to the formation of fine grains are reviewed and the influence of changes in strain path is highlighted. During post-SPD thermal annealing, some typical microstructural changes take place. The influence of SPD and subsequent annealing on strength, ductility and superplastic properties are reviewed. Finally the paper provides a short overview of fatigue resistance and corrosion properties of those materials.

The sticking problem during direct reduction of fine iron ore in the fluidized bed

In this review paper described are possible chemical reactions and their thermodynamic analysis during direct reduction. The sticking mechanism during direct reduction in the fluidized bed was analysed, and the reasons for the sticking appearance explained. The most important parameters on the sticking were analysed. The ways for prevention and observation were considered. The plan for experimental investigations was proposed. The investigations could be performed in fluidized bed reactor. Coal will be used as inert material. Separately, the influence volatile content in the coal on the reduction process and sticking appearance, will be analysed. As results of these investigations would be some improvements of the method direct reduction of iron ore in the fluidized bed.

Comparison of Newtonian and Fourier thermal analysis techniques for calculation of latent heat and solid fraction of aluminum alloys

The cooling curve analysis (CCA) has been used extensively in the metal casting industry, usually to predict alloy compositio n and microstructure constituents. The use of CCA can be expanded to other areas of solidification if the zero curves can be properly calculated. In this paper the Newtonian and Fourier techniques of zero curve determination are described. These techniques were developed to calculate latent heat and to determine the correlations between solid fraction and temperature/time for Al-7 wt%Si alloy. The importance of the changes in heat capacity and density of solid and liquid phases during solidification on the latent heat calculations was examined. The latent heat calculated by Computer-Aided Cooling Curve Analysis (CA-CCA) method is compared with those reported in the literature. The effect of experimental procedure and type of sampling cup on the latent heat calculations were studied for both techniques.