The crystal structure of an M₃B₂-type double boride

Abstract

Two isomorphous borides extracted from different superalloys possess a double boride structure, involving metal atoms of varying size. The structure is tetragonal with c/a = 0.54 and belongs to space group P4/mbm. It consists of larger metal atoms located at the vertices of directly stacked 3 ~ . 4.3.4 semi-regular-tessellation layers with smaller metal atoms at the centers of square prisms and boron at the centers of triangular prisms. Boron atoms occur in isolated bonded pairs. ExperimentalA new boride structure has been found in alloys ttS-88 and Incoloy 901, each with around 0.1% boron addition. The borides were extracted electrolytically from unaged specimens and examined by X-ray powder analysis. Small amounts of TiC were also present in both extracts. Incoloy 901 without boron does not produce this structure.

Solid-State Phase Transformations Involving (Nb,Mo)2CrB2 Borides and (Nb,Ti)2CS Carbosulfides at the Grain Boundaries of Superalloy Inconel 718

“…Yet, the tetragonal structure P4/mbm and a c/a ratio equal to 0.54 are typical of M 3 B 2 borides. [29] The lattice parameters found in the present study were very close to that found by Vincent [20] for his (Nb,Mo,Cr) 3 B 2 borides (a = 5.78 Å and c = 3.16 Å [20] ). However, if Vincent [20] recognized a lack of stoichiometry for his (Nb,Mo,Cr) 3 B 2 borides, here the stoichiometry of the M 3 B 2 structure was rather well respected.…”

“…Indeed, it is known that the M 3 B 2 phase is actually an arrangement of large metallic atoms (L), smaller metallic atoms (S) and boron atoms (B) so that the exact chemical formula is L 2 SB 2 . [20,29] The large metallic atoms are typically Ti, Nb and Mo, while the smaller metallic atoms are typically Cr, Fe and Ni. [20] Here, the TEM-EDX spectrum acquired on the particle 1 of Figure 7 gave the chemical composition 1.2Ti-37.5Nb-26.5Mo-26.5Cr-4.6Fe-2.8Ni at.…”

Review of Microstructure–Mechanical Property Relationships in Cast and Wrought Ni‐Based Superalloys with Boron, Carbon, and Zirconium Microalloying Additions

“…[29,30,39,50,[103][104][105] Mo-rich M 3 B 2 borides have a D5 a tetragonal crystal structure (see Figure 3c) that can be constituted by the general L 2 SB 2 structure where L represents elements with larger atomic radii such as W, Mo, and Ti, while S represents elements with smaller atomic radii such as Cr, Co, and Ni. [30,103,106] Their blocky morphology is shown in Figure 3d. [30] In cast IN939 and Udimet 700, M 3 B 2 borides have been linked to the formation of eutectic pools once the incipient melting temperature is exceeded.…”

“…Figure 8a reveals two domains in the C and B contents. Carbides [12,[26][27][28]40,47,48,54,56,57,[63][64][65]80,81,104,106,108,111,137,143,[221][222][223][224] For a more intuitive representation and a table of the used references, readers are referred to the supporting information. are predominantly preferred above the isoline, below which borides and both, carbides and borides, are preferred.…”

Avaliação do comportamento mecânico em fluência e de oxidação da superliga MAR-M246 convencional e modificada pela substituição do Ta pelo Nb

“…Em geral, quatro tipos de boretos tem sido reportado como precipitados nas superligas de Ni, o M3B2, M5B3, M2B e M23B6, onde M é uma combinação dos elementos metálicos de transição, sendo os dois primeiros as fases mais comuns observadas. No entanto, embora a estrutura cristalina dos boretos M3B2 e M5B3 tenham sido determinados por diferentes técnicas de análise microestrutural, ainda há incerteza sobre como os metais de transição estão distribuídos nos locais da rede cristalográfica, ou seja, se eles estão distribuídos aleatoriamente em diferentes locais ou se preferem ocupar inicialmente alguns locais devido ao seu raio atômico ou sua afinidade química (BEATTIE, 1958;HU et al, 2014HU et al, , 2015HU et al, , 2018. A Figura 4 mostra uma partícula de M3B2 presente no interior do grão de uma superliga à base de Ni.…”