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Upgraded titania slag (UGS) is a titanium-rich material with over 90 wt% titanium dioxide and some minor elements such as Fe, Al, Cr, and Si, which is mainly used for preparing TiO2 and TiCl4. In this study, UGS was directly reduced with magnesium powder in a hydrogen atmosphere. Titanium alloy hydride powder with the oxygen content of 0.032 wt% was obtained. The minor elements of Fe, Si, Al, and Cr from the UGS were kept in the final powder with the main phase of TiH1.924(δ), and minor intermetallic phases of HFe2Ti, Ti5Si3H0.9 and Cr1.8TiH5.3. EDS elemental mapping results indicated that HFe2Ti and Ti5Si3H0.9 intermetallics formed bright phase islands in the matrix. The reduction mechanism and the reaction sequence were discussed based on the thermodynamic modelling with the assistance of HSC chemistry software. The possibility of hydrogen reduction of titanium oxides was discussed as well.

Additive manufacturing is a new emerging technology which is ideal for low-to-zero waste production, and it is considered to be a green and clean process that has the potential to lower the cost and energy consumption of production. However, the cost of the feedstock for additive manufacturing and the additive manufactured parts is usually very high, which hinders the further application of additive manufacturing, especially for the metal additive manufacturing. The concept of circular metal additive manufacturing involves the recycling of the metal feedstock and the additive manufactured parts leading to the truly zero waste production and the most energy saving. This paper reviews the technologies that help the formation of a circular metal additive manufacturing through recycling of the feedstocks and the damaged metal parts. Reactive metals, such as titanium, tend to be contaminated easily during handling and production. Recycling of the titanium for achieving a circular titanium additive manufacturing is reviewed in detail.

A TiTaNbZrHf refractory high-entropy alloy (RHEA) was synthesized through a cold isostatic pressing and a pressure-less sintering process in a hydrogen atmosphere using a powder mixture of metal hydride prepared either by mechanical alloying (MA) or by rotating mixing. This study investigates how differences in powder particle sizes impact the RHEA’s microstructure and mechanical properties. HCP (a = b = 3.198 Å, c = 5.061 Å) and BCC2 (a = b = c = 3.40 Å) phases were observed in the microstructure of coarse powder TiTaNbZrHf RHEAs at 1400 °C. In contrast, fine powder RHEAs were found to possess two-phase structures of HCP and BCC1 (a = b = c = 3.36 Å) with a higher hardness of 431 HV, compression strength of 1620 MPa, and a plasticity of >20%.

Cobalt-chrome-molybdenum (Co-Cr-Mo) alloy possesses outstanding strength, wear, and corrosion resistance and is a good material candidate for making dental and orthopedic implants. Spherical Co-Cr-Mo powder for additive manufacturing is usually costly due to the high-temperature melting processes and low yield of the powder with desirable particle size in the conventional melt-atomization process. A novel process for making spherical Co-Cr-Mo alloy powder through a simple meltless granulation and sintering process is described herein. The results indicate that the compositional segregation problem can be overcome and high-temperature operation avoided. Segregation-free powder was obtained after sintering above 1200°C. The powder was purified during sintering in a hydrogen atmosphere. The hydrogen purification mechanism is discussed with the aid of thermodynamic modeling using HSC Chemistry software. The oxygen content in the final powder can be controlled to

Jamesonite is a significant complex mineral containing antimony, lead, iron and other elements. At present, the traditional smelting method has high sulfur dioxide pollution and low metal recovery. This paper puts forward a method of treating jamesonite by vacuum distillation. The decomposition behavior of jamesonite (Pb4FeSb6S14) in argon and 10 Pa, the volatilization of pure sulfides and the vacuum distillation behavior of jamesonite under 10 Pa were also studied. The separation of lead and antimony via two methods, namely multi-step condensation and one-step multi-stage condensation was developed. The results show that the initial decomposition temperature of jamesonite is higher than 600 °C in argon and about 500 °C at 10 Pa. The final decomposition products are antimony trisulfide, lead sulfide and ferrous sulfide. The decomposition temperature can be effectively reduced under negative pressure. Pure antimony sulfide volatilizes violently at 630 °C-760 °C, and pure lead sulfide sublimates violently at 887–1098 °C, respectively. The purity of antimony sulfide and lead sulfide obtained by multi-step condensation experiment is 99.12% and 98.74%, respectively. The purity of antimony sulfide and lead sulfide obtained by one-step multi-stage condensation is 98.12% and 89.26%, respectively. Zinc sulfide is also enriched by a multi-stage condensation, with a purity of 99.40%. This method can achieve the separation of Sb2S3 and PbS directly from jamesonite, significantly reduce the production cost compared to the traditional process.