Microstructural Transitions during Powder Metallurgical Processing of Solute Stabilized Nanostructured Tungsten Alloys

Exploiting grain boundary engineering in the design of alloys for extreme environments provides a promising pathway for enhancing performance relative to coarse-grained counterparts. Due to its attractive properties as a plasma facing material for fusion devices, tungsten presents an opportunity to exploit this approach in addressing the significant materials challenges imposed by the fusion environment. Here, we employ a ternary alloy design approach for stabilizing W against recrystallization and grain growth while simultaneously enhancing its manufacturability through powder metallurgical processing. Mechanical alloying and grain refinement in W-10 at.% Ti-(10,20) at.% Cr alloys are accomplished through high-energy ball milling with transitions in the microstructure mapped as a function of milling time. We demonstrate the multi-modal nature of the resulting nanocrystalline grain structure and its stability up to 1300 °C with the coarser grain size population correlated to transitions in crystallographic texture that result from the preferred slip systems in BCC W. Field-assisted sintering is employed to consolidate the alloy powders into bulk samples, which, due to the deliberately designed compositional features, are shown to retain ultrafine grain structures despite the presence of minor carbides formed during sintering due to carbon impurities in the ball-milled powders.

Recent Advancements in Metallurgical Processing of Marine Minerals

Polymetallic manganese nodules (PMN), cobalt-rich manganese crusts (CRC) and seafloor massive sulfides (SMS) have been identified as important resources of economically valuable metals and critical raw materials. The currently proposed mineral processing operations are based on metallurgical approaches applied for land resources. Thus far, significant endeavors have been carried out to describe the extraction of metals from PMN; however, to the best of the authors’ knowledge, it lacks a thorough review on recent developments in processing of CRC and SMS. This paper begins with an overview of each marine mineral. It is followed by a systematic review of common methods used for extraction of metals from marine mineral deposits. In this review, we update the information published so far in peer-reviewed and technical literature, and briefly provide the future perspectives for processing of marine mineral deposits.

Prospects for using boron in metallurgy. Report 2

The second part of the article presents perspective directions of using boron and its compounds in the preparation processes, metallurgical processing of ore materials and steel smelting in order to improve the quality of the final product. An efficient technology of silicothermal production of ferrosilicoboron containing 0.6 – 2.0 % B and 60 – 80 % Si has been developed. The advantage of this scheme is the possibility of obtaining a boron-containing alloy during ferrosilicon smelting. It has been experimentally shown that ferrosilicoboron has higher performance characteristics than ferroboron both in production and when used for steel processing. The results of industrial tests of the technology for microalloying pipe grades of steel with a new ferroalloy with boron confirmed a high degree of boron assimilation – up to 96 %. The possibility of widespread use of boron for steel microalloying is due to its cheapness, availability and environmental friendliness. According to the calculations, boron from complex ferrosilicoboron is the cheapest trace element used to increase the strength characteristics of steel. Additives of B2O3 can be successfully used to form high-magnesium liquid steel-making slags. It is shown that 0.37 – 0.55 % В2О3 effectively stabilizes the highly basic slags of the steel and ferroalloy industries. This operation allows obtaining a marketable lump material. The above review, results of the laboratory and industrial studies have shown the effectiveness of boron usage at different stages of metallurgical production. An increase in technical and economic indicators of production and quality of steel and ferroalloys, and effective disposal of waste slags is shown. The technical solutions advanced and tested at metallurgical enterprises do not require capital expenditures. They are implemented by adding microdosing of boron and its compounds to metallurgical production facilities.

Additive Manufacturing of Textured FePrCuB Permanent Magnets

Permanent magnets based on FePrCuB were realized on a laboratory scale through additive manufacturing (laser powder bed fusion, L-PBF) and book mold casting (reference). A well-adjusted two-stage heat treatment of the as-cast/as-printed FePrCuB alloys produces hard magnetic properties without the need for subsequent powder metallurgical processing. This resulted in a coercivity of 0.67 T, remanence of 0.67 T and maximum energy density of 69.8 kJ/m3 for the printed parts. While the annealed book-mold-cast FePrCuB alloys are easy-plane permanent magnets (BMC magnet), the printed magnets are characterized by a distinct, predominantly directional microstructure that originated from the AM process and was further refined during heat treatment. Due to the higher degree of texturing, the L-PBF magnet has a 26% higher remanence compared to the identically annealed BMC magnet of the same composition.

Advanced Methods for Kiln-Shell Monitoring to Optimize the Waelz Process for Zinc Recycling

The recycling of zinc in the Waelz process is an important part of the efficient use of resources in the steel processing cycle. The pyro-metallurgical processing of zinc-containing wastes takes place in a Waelz rotary kiln. Various measured variables are available to monitor the process. The temperature of the kiln-shell is analyzed by an infrared kiln-shell-scanner. In this paper, methods are presented which eliminate external weather-related disturbances on the temperature measured by the kiln-shell-scanner using a weather model and which extend the monitoring of the regularly necessary melting process to remove accretions. For this purpose, an adapted sigmoid estimation is introduced for the melting process, which provides new information about the current process status and a forecast of the further development of the melting process. As an assistance system for the plant operator, this enables an efficient execution of the melting process and reduces downtimes.

Pyro-Metallurgical Processing of Ilmenite Concentrate with Production of Iron and Titanium Oxides

The main problem of processing of ores with a high content of titanium oxides is refractory slag based on TiO2, which makes it difficult to melt. The methods of processing of titanomagnetite and ilmenite ores were analyzed. It is shown that the existing scheme of processing does not meet the requirements of complex use of materials. The paper presents the results of laboratory studies on reduction of ilmenite concentrate and subsequent pyrometallurgical separation of reduction products without addition of flux or slag-forming materials. Solid-phase reduction of iron enabled to extract iron selectively from the ilmenite crystal lattice, not diluting the oxide phase with the reducing agent ash. Using the advantages of solid-phase reduction, the possibility of obtaining pure iron and slag with a high content of titanium oxides was shown.