Thermodynamics of rapid solidification and crystal growth kinetics in glass-forming alloys

Thermodynamic driving forces and growth rates in rapid solidification are analysed. Taking into account the relaxation time of the solute diffusion flux in the model equations, the present theory uses, in a first case, the deviation from local chemical equilibrium, and ergodicity breaking. The second case of ergodicity breaking may exist in crystal growth kinetics of rapidly solidifying glass-forming metals and alloys. In this case, a theoretical analysis of dendritic solidification is given for congruently melting alloys in which chemical segregation does not occur. Within this theory, a deviation from thermodynamic equilibrium is introduced for high undercoolings via gradient flow relaxation of the phase field. A comparison of the present derivations with previously verified theoretical predictions and experimental data is given. This article is part of the theme issue 'Heterogeneous materials: Metastable and nonergodic internal structures'. ©2019 The Author(s) Published by the Royal Society

Laser Cladding and Additive Manufacturing Technologies Using High-Entropy, Ceramic and Multilayer Materials

Рассмотрено получение теплостойких покрытий и деталей из высокоэнтропийных сплавов лазерными наплавкой и выращиванием. Высокоскоростным селективным лазерным плавлением создаются сверхтвердые покрытия на основе карбида и нитрида бора. Предложена комбинированная постобработка изделий аддитивного производства с формированием многослойных тонкопленочных покрытий.The review considers the production of heat-resistant coatings and parts from high-entropy alloys by laser cladding and additive manufacturing. High-speed selective laser melting creates superhard coatings based on boron carbide and boron nitride. A combined post-processing of additive manufacturing products with the formation of multilayer thin-film coatings is proposed.Работа выполнена в рамках государственных заданий ИФМ УрО РАН по теме № АААА-А18-118020190116-6 и ИМАШ УрО РАН по теме № АААА-А18-118020790147-4 при поддержке гранта РФФИ № 20-48­660065 и Свердловской области в части постобработки деталей аддитивного производства с формированием тонкопленочного покрытия. Исследование также поддержано проектом № IRA-SME‑66316 «cladHEA+» по программе M‑ERA. NET, Call 2019‑II в части получения покрытий из высокоэнтропийных сплавов лазерной наплавкой.The work was carried out within the framework of the state tasks of the IFM of the Ural Branch of the Russian Academy of Sciences on the topic no. AAAA18–118020190116–6 and IMASH of the Ural Branch of the Russian Academy of Sciences on the topic no. AAAA18-118020790147-4 with the support of the RFBR grant no. 20-48-660065 and the Sverdlovsk region in terms of post-processing of additive manufacturing parts with the formation of thin-film coating. The research is also supported by the project No. IRA-SME‑66316 “cladHEA+” under the program M‑ERA. NET, Call 2019‑II in terms of obtaining coatings from high-entropy alloys by laser surfacing

Powder bed generation in integrated modelling of additive layer manufacturing of orthopaedic implants

This paper presents an original model of powder bed generation developed within the frame of an integrated modelling approach for studying the interaction of physical mechanisms in additive layer manufacturing (ALM) of orthopaedic implants. The model is based on cellular automata (CA) approach and describes the relationship between moving particles of different sizes during deposition on a surface in three dimensions. The surface is defined by the horizontal two-dimensional CA on which particles fall and irreversibly stick to a growing deposit. The model allows for consideration of different restructuring cases when particles are allowed to rotate as often as necessary until achievement of a local minimum position. Changes in the packing density of the powder bed have been investigated numerically depending on technological parameters, such as particle size distribution, deposition rate and sequence of powder deposition. The model has been developed with the aim of merging to the finite element (FE)-based integrated model and is applicable to a different ranges of materials including metals and also non-metals