Defect phases – thermodynamics and impact on material properties

Abstract

Two approaches in materials physics have proven immensely successful in alloy design: First, thermodynamic and kinetic descriptions for tailoring and processing alloys to achieve a desired microstructure. Second, crystal defect manipulation to control strength, formability and corrosion resistance. However, to date, the two concepts remain essentially decoupled. A bridge is needed between these powerful approaches to achieve a single conceptual framework. Considering defects and their thermodynamic state holistically as 'defect phases', provides a future materials design strategy by jointly treating the thermodynamic stability of both, the local crystalline structure and the distribution of elements at defects. Here, we suggest that these concepts are naturally linked by defect phase diagrams describing the coexistence and transitions of defect phases. Construction of these defect phase diagrams will require new quantitative descriptors. We believe such a framework will enable a paradigm shift in the description and design of future engineering materials.

Effect of Sn on Generalized Stacking Fault Energy Surfaces in Zirconium and its Hydrides

“…With our analysis we understand not only a Sn decoration of stacking faults, but also the reason for the formation of stacking faults inside the hydride. The chemical stabilization of the defects by Sn, which would otherwise not be present, belongs to the category of defect phases [37] that are currently reported for various materials systems [38].…”

On Strong-Scaling and Open-Source Tools for High-Throughput Quantification of Material Point Cloud Data: Composition Gradients, Microstructural Object Reconstruction, and Spatial Correlations

“…Literature results from early APFIM measurements [130,131] which relied on a different methodological approach than compared to modern APT measurements also report such narrow segregation profiles for W-Re solid solutions. The here proposed protocol for automated characterization of gradients at interfaces can support research on disentangling the individual contributions of inaccuracies due to reconstruction models used or the eventual existence of defect phases [132], and/or precipitates at the interface. Whether such a disentangling is possible with experiments alone or requires the support of computer simulations is a topic of current research [57].…”

“…Specifically, an example of research on characterizing the composition of metastable phases in a metastable titanium alloy. The challenge here is that thermodynamics enable eventually for a range of object compositions, which can oftentimes be very similar, especially when defect phases [132] are involved and finite counting effects are relevant [137]. Specifically, the user story summarizes practical research experiences from a recent analysis by Zheng and coworkers [138,139].…”

Defect-characterized phase transition kinetics

“…Indeed, there have been significant advances in theoretical and experimental techniques in recent years that allow to probe the microscopic mechanisms of defect-characterized phase transition kinetics. [48][49][50][51][52][53][54][55][56][57][58][59][60][61][62] Conceptually, the idea of "defect phases" has recently been proposed, 63 which focuses more on the thermodynamic aspects. In this review, we will use selected examples to demonstrate the various roles that defects can play in phase transition kinetics.…”