The fundamental assumption of metallography is supported by the deterministic relationship between on the one hand microscopic arrangements of phases and defects, and on the other hand macroscopic properties (such as strength, stiffness and plasticity) which determine the materials function: If the microstructure is highly anisotropic, macroscopic properties will not be isotropic. If microscopic stress is high, the material is brittle. If grains are smaller than one micrometer, the macroscopic strength rises.
For multiphase materials such as aluminum-silicon alloy and cast iron our work demonstrates how – in particular – three-dimensional structural parameters, such as connectivity and continguity, strongly influence macroscopic strength. By tailoring the complex three-dimensional morphology of the alloys’ phases through composition, cooling and thermo-mechanical treatment one can establish a multidimensional materials database. Such a database – once established – would allow optimizing any alloy according to its functional use. Such an optimization is already applied to cast alloy components in the automotive sector. Characterizing metallic microstructures by X-ray micro and nano computed tomography (CT), one can also attempt tailoring the corrosive properties of magnesium alloy to make them bio-degradable, yet high-strength, implants for hips and joints. Finally, we will elaborate on the option to use micro- and nano-CT data as building blocks for finite element models in process- and structural simulations. By assigning linear elastic and thermal properties to each materials phase and by numerically evaluating the tensor components of each property in a mesh with 0,1 – 1 mm length, one can create a complete materials model on a much larger scale. For anisotropic structures – of course – representative measures have to be taken at several locations, e.g. by means of small angle X-ray scattering (SAXS). The latter can also be used to sense and quantify nanometer-sized precipitates, e.g. for studying aging in aluminum alloys.
In conclusion, X-ray micro and nano computed tomography and SAXS have become indispensable tools for the characterization of metallic and non-metallic microstructures on a sub-micrometer scale. Paving the way to the “smart materials dataspace” the quest for extraction of meaningful stochastic parameters from 3D CT scans of metallic alloys is now more prominent than ever.