In the present study, the microstructure development and mechanical properties of the cast boron-rich Fe–B–C alloys cooled at 10 and 103 K/s were investigated as functions of alloying elements additions. These alloys were prepared in the following compositional ranges: B (10–14 wt.%), C (0.1–1.2 wt.%), M (5 wt.%), where M – Cu, Ni or Mn, balance Fe. Structural properties were characterized by quantitative metallography, X-Ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. Mechanical properties of the structural constituents, such as microhardness and fracture toughness, were measured by a Vickers indenter. Copper becomes negligibly incorporated into the phases Fe(B,C) and Fe2(B,C) of the Fe–B–C alloys, but solubility limit forces the remaining solute into the residual liquid. As a result, the globular Cu inclusions are seen in the structure. As compared with copper, nickel has higher solubility in the constituent phases, with preferential solubility observed in the Fe2(B,C) crystals, where Ni occupies Fe positions. Having limited solubility, nickel also forms secondary Ni4B3 phase at the Fe2(B,C) boundaries. Manganese was found to dissolve completely in the Fe–B–C alloys forming substitutional solid solutions preferentially with Fe(B,C) dendrites. By entering into the iron borides structure, Mn and Ni improve their ductility but lower microhardness. The peculiarities in the structure formation and properties of the doped boron-rich Fe–B–C alloys were explained with electronic structure of the alloying elements considered.

В работе исследована структура квазикристаллических сплавов Al 65 Co 20 Cu 15 и Al 72 Co 18 Ni 10 , а также композиционных материалов на их основе, полученных методом печной пропитки. Использованы методы металлографического, рентгеноструктурного, электронно-микроскопического и микрорентгеноспектрального анализов. В сплаве Al 65 Co 20 Cu 15 квазикристаллическая декагональная фаза сосуществует с кристаллическими фазами Al 4 (Co, Cu) 3 и Al 3 (Cu, Co) 2 , а в сплаве Al 72 Co 18 Ni 10-с фазами Al 9 (Co 1−х Ni х) 2 и Al 9 (Ni 1−х Co х) 2. Содержание квазикристаллической фазы в сплавах колеблется в пределах 60-65% об. С помощью оригинальной методики автоматизированного структурного анализа построены кривые распределения коэффициентов поглощения света, использованные для расчёта энтропии фаз. В ходе пропитки латунной связкой марки Л62 гранул наполнителей, изготовленных из сплавов Al 65 Co 20 Cu 15 или Al 72 Co 18 Ni 10 , расплавленная связка растворяет кристаллические фазы наполнителя, проникая до центра гранул. При этом квазикристаллическая фаза наполнителей растворяется с гораздо меньшей скоростью. В структуре композиционного материала, упрочнённого сплавомнаполнителем Al 65 Co 20 Cu 15 , содержание квазикристаллической фазы на 15% об. превышает содержание этой фазы в композиционном материале с

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In the present study, the microstructure development and properties of the starting Fe-B-C powders for plasma spraying fabricated by dispersing a consumable rotating rod were investigated as functions of alloying elements additions. These powders were prepared in the following compositional ranges: B (10…14 wt.%), C (0.01…0.5 wt.%), Me (0…5.0 wt.%), where Me – Cr, V, Mo or Nb, balance Fe. Structural properties were characterized by etallography, X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. Mechanical properties of the powders were measured by a Vickers indenter. Compression strength, oxidation resistance, and melting temperature were also determined. Chromium or vanadium were found to dissolve completely in Fe2(B, C) and Fe(B, C) constituent phases of the Fe-B-C powders replacing iron and forming substitutional solid solutions. By entering into the iron borides structure, these alloying elements improve ductility and oxidation resistance but lower melting temperature and hardness of the powders. Molybdenum or niobium were mainly found in secondary phases such as Mo2B, Mo2(B, C) or NbB2 at the Fe2(B, C) boundaries. As a result, these alloying elements enhance hardness, oxidation resistance and melting temperature of the powders.