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Formation and characterization of an Al‐rich metastable phase in the Al–B phase diagram
Author(s) -
Malkin Alexander I.,
Chernyshev Vladimir V.,
Ryazantseva Alena A.,
Vasiliev Alexander L.,
Nickolsky Maximilian S.,
Shiryaev Andrei A.
Publication year - 2021
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s1600576721005756
Subject(s) - metastability , nucleation , phase diagram , phase (matter) , boron , materials science , crystallography , aluminium , thermal stability , standard enthalpy of formation , diffraction , thermodynamics , allotropy , chemistry , metallurgy , physics , organic chemistry , optics
Vacuum heat treatment of mechanically alloyed powders of boron and aluminium leads to the formation of a metastable Al‐rich phase, which can be quenched. Its structure, composition and thermal stability are established. With the chemical formula Al 1.28 B the rhombohedral phase is unusually rich in Al. The parameters of the unit cell determined from X‐ray powder diffraction are a = 18.3464 (19), c = 8.9241 (9) Å, V = 2601.3 (6) Å 3 , space group R 3 . It is stable on heating to 630°C. It is suggested that this phase is an important intermediate step in the formation of AlB 2 and, eventually, of other borides; its nucleation and thermal stability are explained by high elastic energy hindering the formation of equilibrium phases at low temperatures.