X-ray computer tomography (CT) is fast becoming an accepted tool within the materials science community for the acquisition of 3D images. Here the authors review the current state of the art as CT transforms from a qualitative diagnostic tool to a quantitative one. Our review considers first the image acquisition process, including the use of iterative reconstruction strategies suited to specific segmentation tasks and emerging methods that provide more insight (e.g. fast and high resolution imaging, crystallite (grain) imaging) than conventional attenuation based tomography. Methods and shortcomings of CT are examined for the quantification of 3D volumetric data to extract key topological parameters such as phase fractions, phase contiguity, and damage levels as well as density variations. As a non-destructive technique, CT is an ideal means of following structural development over time via time lapse sequences of 3D images (sometimes called 3D movies or 4D imaging). This includes information nee...

https://www.tandfonline.com/doi/pdf/10.1179/1743280413Y.0000000023

Quantitative X-ray tomography

This review highlights recent advances in X-ray microcomputed tomography (microCT) as applied to materials, specifically advances made since the first materials microCT review appeared in Internati...

Recent advances in X-ray microtomography applied to materials

Virtually all known drinking water processing systems generate an enormous amount of residual sludge, and what to do with this rapidly increasing “waste” stream in an economic and environmentally sustainable manner remains a significant environmental issue. Perhaps the realization of this fact has led to a series of concerted efforts aimed at beneficial reuses in an effort to close the loop between efficient water treatment and sustainable sludge management. This article therefore presents a comprehensive review of available literature on attempts at beneficial reuses of water treatment plant sludge, in an effort to provide a compendium of recent and past developments, and to update our current state of knowledge. Four broad categories of uses, which included more than 11 possible ways in which waterworks sludges can be reused, are identified and examined. Obvious advantages of such reuse options are highlighted and knowledge gaps are identified. Future issues that will assist in the development of sustainable waterworks sludge management options with a multiprong approach are discussed.

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Constructive Approaches Toward Water Treatment Works Sludge Management: An International Review of Beneficial Reuses

Defects in additive manufactured metals and their effect on fatigue performance: A state-of-the-art review

Differential scanning calorimetry (DSC) and isothermal calorimetry have been applied extensively to the analysis of light metals, especially Al based alloys. Isothermal calorimetry and differential scanning calorimetry are used for analysis of solid state reactions, such as precipitation, homogenisation, devitrivication and recrystallisation; and solid–liquid reactions, such as incipient melting and solidification, are studied by differential scanning calorimetry. In producing repeatable calorimetry data on Al alloys, sample preparation, reproducibility and baseline drift need to be considered in detail. Calorimetry can be used effectively to study the different solid state reactions and solid–liquid reactions that occur during the main processing steps of Al based alloys (solidification, homogenisation, precipitation). Also, devitrivication of amorphous and ultrafine grained Al based powders and flakes can be studied effectively. Quantitative analysis of the kinetics of reactions is assessed through reviewing the interrelation between activation energy analysis methods, equivalent time approaches, impingement parameter approaches, mean field models for precipitation, the Johnson–Mehl–Avrami–Kolmogorov model, as well as novel models which have not yet found application in calorimetry. Differential scanning calorimetry has occasionally been used in attempts to measure the volume fractions of phases present in Al based alloys, and attempts at determining volume fractions of intermetallic phases in commercial alloys and amounts of devitrified phase in glasses are reviewed. The requirements for the validity of these quantitative applications are also reviewed.

/pdf/analysis-of-aluminium-based-alloys-by-calorimetry-1479axcy9w.pdf

Analysis of aluminium based alloys by calorimetry: quantitative analysis of reactions and reaction kinetics

The behaviour of titanium diboride particles in molten aluminium was investigated by conducting casting experiments at different cooling rates and particle addition levels, starting with a master alloy containing in situ formed TiB2 particles. The particle pushing/engulfment phenomena and particle clustering effects were studied for two matrix alloy systems, commercial purity (CP) aluminium and an Al-4% Mg (A514) alloy. The critical velocity, which is the solidification velocity below which the particles are pushed and above which they are engulfed, was calculated. The results were validated against the predictions of the models available in the literature. The assumptions, limitations and comparative success of the different models were discussed. The critical velocity observed in CP-Al ranged between 4 and 8 μm/s at low particulate concentration ( The hypothesis that particle clustering could result in erroneous critical velocity predictions was explored and it was concluded that particle clustering must be included for accurate prediction of particle pushing in these alloys.

Effect of clustering on particle pushing and solidification behaviour in TiB2 reinforced aluminium PMMCs

Thermophysical properties for the solid and liquid phases of several Ni based superalloys (CMSX-4, CMSX-10, CM186LC, IN 738 and Rene 80) have been measured. The following properties were measured: heat capacity and enthalpy, thermal expansion coefficient and density, thermal diffusivity, viscosity and surface tension. Analysis of these measurements showed that that γ′ phase (Ni3Al) affected the values for the following properties; C p, enthalpy, electrical resistivity, thermal diffusivity and conductivity. Relationships have been identified between properties and the γ′ phase content (which can be represented by mass% Al in the alloy). These relations were then used to calculate property values of the alloys from chemical composition. Other relations were developed to estimate the viscosities and surface tensions of Ni based superalloys. The predicted property values were found to be in good agreement with the measured values.

/pdf/measurement-and-estimation-of-thermophysical-properties-of-24663rv8pm.pdf

Measurement and estimation of thermophysical properties of nickel based superalloys

Ti6Al4V alloy has received a great deal of attention in medical applications due to its biomechanical compatibility. However, the human bone stiffness is between 10 and 30 GPa while solid Ti6Al4V is several times stiffer, which would cause stress shielding with the surrounding bone, which can lead to implant and/or the surrounding bone’s failure.,In this work, the effect of selective laser melting (SLM) process parameters on the characteristics of Ti6Al4V samples, such as porosity level, surface roughness, elastic modulus and compressive strength (UCS), has been investigated using response surface method. The examined ranges of process parameters were 35-50 W for laser power, 100-400 mm/s for scan speed and 35-120 µm for hatch spacing. The process parameters have been optimized to obtain structures with properties very close to that in human bones.,The results showed that the porosity percentage of a SLM component could be increased by reducing the laser power and/or increasing the scan speed and hatch spacing. It was also shown that there was a reverse relationship between the porosity level and both the modulus of elasticity and UCS of the SLM part. In addition, the increased laser power was resulted into a substantial decrease of the surface roughness of SLM parts. Results from the optimization study revealed that the interaction between laser process parameters (i.e. laser power, laser speed, and the laser spacing) have the most significant influence on the mechanical properties of fabricated samples. The optimized values for the manufacturing of medical implants were 49 W, 400 mm/s and 99 µm for the laser power, laser speed and laser spacing, respectively. The corresponding porosity, surface roughness, modulus of elasticity and UCS were 23.62 per cent, 8.68 µm, 30 GPa and 522 MPa, respectively.,Previous investigations related to additive manufacturing of Ti alloys have focused on producing fully dense and high-integrity structures. There is a clear gap in literature regarding the simultaneous enhancement and adjustment of pore fraction, surface and mechanical properties of Ti6Al4V SLM components toward biomedical implants. This was the objective of the current study.

/pdf/optimization-of-slm-process-parameters-for-ti6al4v-medical-5bmbl0fh5d.pdf

Optimization of SLM Process Parameters for Ti6Al4V Medical Implants

Reliable thermophysical data of Ni-based superalloys are needed for the mathematical modelling of solidification in casting applications. This paper derives equations and procedures to calculate the following properties of these alloys from chemical composition of the alloy: the γ′ phase content, liquidus and solidus temperatures, density and thermal expansion coefficient, heat capacity and enthalpy, electrical resistivity, thermal diffusivity and conductivity, viscosity, surface tension and contact angle. Estimates are also for the diffusion coefficient and emissivity. This work has revealed an urgent need for reliable property measurements on liquid Ni-based alloys for the following: heat capacity, electrical resistivity, thermal diffusivity and conductivity, emissivity and diffusion coefficients.

Y. M. Youssef

Papers

Effect of clustering on particle pushing and solidification behaviour in TiB2 reinforced aluminium PMMCs

Measurement and estimation of thermophysical properties of nickel based superalloys

Optimization of SLM Process Parameters for Ti6Al4V Medical Implants

Calculation of Thermophysical Properties of Ni-based Superalloys

Evolution of pore morphology and distribution during the homogenization of direct chill cast Al-Mg alloys