Laves phases with their comparably simple crystal structure are very common intermetallic phases and can be formed from element combinations all over the periodic table resulting in a huge number of known examples. Even though this type of phases is known for almost 100 years, and although a lot of information on stability, structure, and properties has accumulated especially during the last about 20 years, systematic evaluation and rationalization of this information in particular as a function of the involved elements is often lacking. It is one of the two main goals of this review to summarize the knowledge for some selected respective topics with a certain focus on non-stoichiometric, i.e., non-ideal Laves phases. The second, central goal of the review is to give a systematic overview about the role of Laves phases in all kinds of materials for functional and structural applications. There is a surprisingly broad range of successful utilization of Laves phases in functional applications comprising Laves phases as hydrogen storage material (Hydraloy), as magneto-mechanical sensors and actuators (Terfenol), or for wear- and corrosion-resistant coatings in corrosive atmospheres and at high temperatures (Tribaloy), to name but a few. Regarding structural applications, there is a renewed interest in using Laves phases for creep-strengthening of high-temperature steels and new respective alloy design concepts were developed and successfully tested. Apart from steels, Laves phases also occur in various other kinds of structural materials sometimes effectively improving properties, but often also acting in a detrimental way.

The present works assesses the knowledge concerning the crystal structures of phases in the Cu–Sn system having their high relevance due to their occurrence in bronze alloys and soldered systems. The crystal structures of the terminal solid solution phases α-Cu and β-Sn and of the stable main intermediate phases β, γ, ε-Cu₃Sn, δ-Cu₄₁Sn₁₁, ζ-Cu₁₀Sn₃, η-Cu₆Sn₅ and η′-Cu₆Sn₅ and some metastable phases appear to be well established in the literature, but details can be intriguing. This paper attempts to review apparently or truly contradictory structure models derived from experimental diffraction data for the different phases, revealing limiting knowledge in some cases. These results are also analyzed regarding the results of first-principles calculations making use of various model structures. The review is also used to highlight exemplarily problems, which can be experienced upon widespread, “routine” means of phase identification, in particular x-ray diffraction (on polycrystalline specimens) and electron backscatter diffraction.

Separation of size and strain effects on diffraction line profiles has been studied in a round robin involving laboratory instruments and synchrotron radiation beamlines operating with different radiation, optics, detectors and experimental configurations. The studied sample, an extensively ball milled iron alloy powder, provides an ideal test case, as domain size broadening and strain broadening are of comparable size. The high energy available at some synchrotron radiation beamlines provides the best conditions for an accurate analysis of the line profiles, as the size–strain separation clearly benefits from a large number of Bragg peaks in the pattern; high counts, reliable intensity values in low-absorption conditions, smooth background and data collection at different temperatures also support the possibility to include diffuse scattering in the analysis, for the most reliable assessment of the line broadening effect. However, results of the round robin show that good quality information on domain size distribution and microstrain can also be obtained using standard laboratory equipment, even when patterns include relatively few Bragg peaks, provided that the data are of good quality in terms of high counts and low and smooth background.

The study of next generation high energy accelerators based on 16 T dipoles has emphasized the need for higher performance, cost-effective $Nb_{3}Sn$ superconducting wires. A Conductor Development Program aiming to reach a non-copper critical current density ( $J_{c}$ ) of 1500 $A/mm^2$ at 16 T and 4.2 K has been launched by CERN, with the involvement of industry and laboratories worldwide. In this article, the targets and strategy of the program are presented, with an overview of the wire layouts and development activities being pursued by each partner, and the latest characterization results are reported. Three of the four participating manufacturers have successfully reached the first stage $J_{c}$ milestone, but a significant advance is still needed to achieve the final target. The next steps are briefly discussed, as the program focuses increasingly on novel alloys and methods to maximize $J_{c}$ .