Self-propagating high-temperature synthesis provides an attractive practical method for producing advanced materials such as ceramics, composites and intermetallics. This kind of reaction has been investigated in situ using time-resolved X-ray diffraction, with an X-ray synchrotron beam (D43 beamline, LURE, Orsay) coupled to simultaneous IR thermography to study structural transformations and thermal evolution. With short acquisition times (30 ms per pattern) it has been possible to observe several steps before obtaining compounds. Two different compound formations have been described: (i) the different steps of reaction, aluminium melting, subsequent temperature increase and fast reaction between Al and Ni at such temperatures that only Ni and AlNi are solid and all other compositions are liquid and well identified; (ii) the formation of FeAl. Here, a portion of the iron seems to transform into its allotropic phase and this transition stabilizes the reaction temperature at approximately 1173 K. In addition, the aluminium melting during the reaction explains why the nanostructure induced by the mechanical activation is maintained in the end product.
[1]
E. Gaffet,et al.
Enhancement of self-sustaining reaction by mechanical activation: case of an FeSi system
,
1999
.
[2]
B. Zeghmati,et al.
Mechanically activated synthesis studied by X-ray diffraction in the Fe–Al system
,
1999
.
[3]
J. Gachon,et al.
Real time X-ray diffraction study of the formation by SHS of the phases γ′ and H in the ternary system AlNiTi
,
1997
.
[4]
J. Chevreul,et al.
Powder diffraction for solid state reaction studies
,
1993
.
[5]
E. Gaffet.
Ball milling : an E-v-T parameter phase diagram
,
1991
.
[6]
J. B. Holt,et al.
Time-Resolved X-ray Diffraction Study of Solid Combustion Reactions
,
1990,
Science.
[7]
T. Takasugi,et al.
Electronic and structural studies of grain boundary strength and fracture in L12 ordered alloys—III. On the effect of stoichiometry
,
1987
.
[8]
Lawrence H. Bennett,et al.
Binary alloy phase diagrams
,
1986
.