The current understanding of the fundamentals of recrystallization is summarized. This includes understanding the as-deformed state. Several aspects of recrystallization are described: nucleation and growth, the development of misorientation during deformation, continuous, dynamic, and geometric dynamic recrystallization, particle effects, and texture. This article is authored by the leading experts in these areas. The subjects are discussed individually and recommendations for further study are listed in the final section.

/pdf/current-issues-in-recrystallization-a-review-12181rj4pn.pdf

Current issues in recrystallization: a review

Flexible electronics and other nanoscale devices require simple yet reliable assembly procedures. An optical welding technique for metal nanowires, based on surface plasmon resonances, is now used to fabricate interconnected nanowire networks with enhanced electrical properties for use as transparent electrodes in solar cells and other electrical devices.

/pdf/self-limited-plasmonic-welding-of-silver-nanowire-junctions-1weoppggxv.pdf

Self-limited plasmonic welding of silver nanowire junctions

After almost three decades of intensive fundamental research and development activities, intermetallic titanium aluminides based on the ordered γ-TiAl phase have found applications in automotive and aircraft engine industry. The advantages of this class of innovative high-temperature materials are their low density and their good strength and creep properties up to 750 °C as well as their good oxidation and burn resistance. Advanced TiAl alloys are complex multi-phase alloys which can be processed by ingot or powder metallurgy as well as precision casting methods. Each process leads to specific microstructures which can be altered and optimized by thermo-mechanical processing and/or subsequent heat treatments. The background of these heat treatments is at least twofold, i.e., concurrent increase of ductility at room temperature and creep strength at elevated temperature. This review gives a general survey of engineering γ-TiAl based alloys, but concentrates on β-solidifying γ-TiAl based alloys which show excellent hot-workability and balanced mechanical properties when subjected to adapted heat treatments. The content of this paper comprises alloy design strategies, progress in processing, evolution of microstructure, mechanical properties as well as application-oriented aspects, but also shows how sophisticated ex situ and in situ methods can be employed to establish phase diagrams and to investigate the evolution of the micro- and nanostructure during hot-working and subsequent heat treatments.

Design, Processing, Microstructure, Properties, and Applications of Advanced Intermetallic TiAl Alloys†

This paper provides an overview on the current understanding of electromigration in metals. The discussion is first focused on studies in bulk metals and alloys. This part includes a thermodynamic formulation of electromigration, a kinetic analysis of the atomic processes and a review of the theory. In addition, experimental results in interstitial and substitutional systems are summarised. The second part of the paper reviews the studies in metallic thin films. This emerged as an important area of electromigration studies since the late 1960s when electromigration damage was found to cause failure of conductor lines in integrated circuits. The discussion will review first the basic nature of electromigration in thin films with emphasis on the role of grain boundaries in mass transport and damage formation. Then the materials issues of electromigration will be explored according to the scaling trends in VLSI technology. Finally, the recent results of electromigration in fine lines and device contacts of dimensions in the micrometre range are discussed.

https://iopscience.iop.org/article/10.1088/0034-4885/52/3/002/pdf

Electromigration in metals

Grain Boundary Complexions

Diffusion in the Ti–Al system

Grain boundary (GB) diffusion often controls the evolution of structure and properties of engineering materials at elevated temperatures. A knowledge of diffusion characteristics of GBs and deep fundamental understanding of this phenomenon are critical to many materials applications. In this paper we give an overview of boundary diffusion theory with emphasis on the interpretation of concentration profiles measured in diffusion experiments. We consider the most important situations encountered in boundary diffusion experiments, such as diffusion in the B and C regimes and diffusion in the presence of segregation. We also discuss the recent progress in the atomistic interpretation of GB diffusion. We conclude with an outlook for future research in this area.

Grain boundary diffusion: recent progress and future research

Grain boundary self-diffusion in Cu polycrystals of different purity

The phonon dispersion of the high-temperature bcc phase of Zr has been measured at several temperatures. The longitudinal L 2/3(1,1,1) mode and the transverse ${\mathrm{T}}_{1}$ 1/2(1,1,0) mode with [11\ifmmode\bar\else\textasciimacron\fi{}0] polarization are of very low energy (i.e., of large amplitude) and overdamped. These phonons achieve the displacements necessary for two martensitic phase transitions. The L 2/3(1,1,1) phonon displaces the lattice toward the high-pressure \ensuremath{\omega} phase and the ${\mathrm{T}}_{1}$ 1/2(1,1,0) phonon shifts the bcc planes into the stacking sequence of the low-temperature hcp phase. These fluctuations are interpreted as dynamical precursors of the low-symmetry phases within the bcc phase. Elastic precursors or central peaks were not found in pure bcc Zr. Furthermore, it is shown that the bcc phase is stabilized mainly by the excess vibrational entropy due to the low-energy phonons.

Chr. Herzig

Papers

Diffusion in the Ti–Al system

Grain boundary diffusion: recent progress and future research

Grain boundary self-diffusion in Cu polycrystals of different purity

Phonon dispersion of the bcc phase of group-IV metals. II. bcc zirconium, a model case of dynamical precursors of martensitic transitions

Self-diffusion in γ-TiAl: an experimental study and atomistic calculations