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Austenite reversion during tempering of a Fe-13.6Cr-0.44C (wt.%) martensite results in an ultrahigh strength ferritic stainless steel with excellent ductility. The austenite reversion mechanism is coupled to the kinetic freezing of carbon during low-temperature partitioning at the interfaces between martensite and retained austenite and to carbon segregation at martensite-martensite grainboundaries. An advantage of austenite reversion is its scalability, i.e., changing tempering time and temperature tailors the desired strength-ductility profiles (e.g. tempering at 400°C for 1 min. produces a 2 GPa ultimate tensile strength (UTS) and 14% elongation while 30 min. at 400°C results in a UTS of ~ 1.75 GPa with an elongation of 23%). The austenite reversion process, carbide precipitation, and carbon segregation have been characterized by XRD, EBSD, TEM, and atom probe tomography (APT) in order to develop the structure-property relationships that control the material's strength and ductility.

Magnetic properties of spinel zinc ferrites are strongly linked to the synthesis method and the processing route since they control the microstructure of the resulting material. In this work, ZnFe 2 O 4 nanoparticles were synthesized by the mechanochemical reaction of stoichiometric ZnO and α-Fe 2 O 3 , and single-phase ZnFe 2 O 4 was obtained after 150 h of milling. The as-milled samples, with a high inversion degree, were subjected to different thermal annealings up to 600 °C to control the inversion degree and, consequently, the magnetic properties. The as-milled samples, with a crystallite size of 11 nm and inversion degree δ = 0.57, showed ferrimagnetic behavior even above room temperature, as shown by Rietveld refinements of the X-ray diffraction pattern and superconducting quantum interference device magnetometry. The successive thermal treatments at 300, 400, 500, and 600 °C decrease δ from 0.57 to 0.18, affecting the magnetic properties. A magnetic phase diagram as a function of δ can be inferred from the results: for δ < 0.25, antiferromagnetism, ferrimagnetism, and spin frustration were observed to coexist; for 0.25 < δ < 0.5, the ferrimagnetic clusters coalesced and spin glass behavior vanished, with only a pure ferrimagnetic phase with a maximum magnetization of M s = 3.5μ B remaining. Finally, for δ > 0.5, a new antiferromagnetic order appeared due to the overpopulation of nonmagnetic Zn on octahedral sites that leads to equally distributed magnetic cations in octahedral and tetrahedral sites.

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The exposure of carbon steel in marine atmospheres can lead in certain circumstances to the formation of thick rust layers (containing a number of compact laminas) that are easily detached (exfoliated) from the steel substrate, leaving it unprotected and considerably accelerating the corrosion process. This deterioration phenomenon is of particular concern in steel infrastructures located close to the sea (civil constructions, bridges, etc.), whose service lifetime can be extraordinarily limited. High times of wetness of the metallic surface and high chloride ion deposition rates play a decisive role in the formation of this type of rust. Research has been carried out for 1 year in eight pure marine atmospheres with annual average chloride deposition rates of 70–1906 mg Cl-/m2 day. The studied carbon steels consisted of one mild steel, one conventional weathering steel (Corten A), and one high nickel (~3 wt.%) advanced weathering steel (AWS). The paper describes the environmental conditions that lead to the formation of these thick multilaminar rust layers and presents a characterisation study of this singular type of rust using a variety of analysis techniques: scanning electron microscopy/energy-dispersive X-ray spectroscopy, X-ray diffraction, Mössbauer spectroscopy, and transmission electron microscopy/electron diffraction. The Ni-AWS shows greater resistance to the occurrence of rust exfoliation.