Abstract
In order to enhance the negligible low-temperature ductility and low high-temperature strength of nickel aluminides, NiAl/TiC composites were fabricated by the combustion reaction process from elemental powders. In this study, the effects of Fe on the combustion reaction of Ni-Al-Ti-C system were studied and mechanical properties of NiAl/TiC composites prepared by the combustion reaction process, following arc-melting were also estimated. The matrix compositions of the alloys included Ni50Fe10Al40, Ni50Fe20Al30 and Ni25Fe50Al25, with TiC of 0-50 at%, respectively.
The addition of Fe significantly reduced the heat of formation during the combustion reaction in Ni-Al-Ti-C system. Resulting compacts consisted of small TiC particles of about 0.5μm and the matrix NiAl. In the arc-melted and annealed specimens, TEM observation revealed that γ-Ni phase appeared on the grain boundaries in Ni50Fe10Al40 alloys, and α -Fe phase precipitated in the matrix in Ni25Fe50Al25 alloys. For Ni50Fe10Al40 alloys, ductility in bending increased because of the γ-Ni phase. The other hand, for Ni25Fe50Al25 alloys, compressive strength pronouncedly increased at ambient and elevated temperatures, caused to the presence of α-Fe phase and TiC particles in the matrix.
