Hs. Park et al., Microstructural refinement and mechanical properties improvement of elemental powder metallurgy processed Ti-46.6Al-1.4Mn-2Mo alloy by carbon addition, MET MAT T A, 32(2), 2001, pp. 251-259
Strengthening of a gamma TiAl alloy was sought by a chemical modification o
f the composition with carbon. Up to 0.6 at. pet of carbon was added to the
Ti-46.6Al-1.4Mn-2Mo alloy processed by elemental powder metallurgy. Carbon
addition resulted in considerable microstructural changes such as refineme
nt, by a factor of about. 2, of the lamellar microstructure and carbide pre
cipitation. The cause of the lamellar structure refinement is twofold, incr
eased heterogeneous nucleation rate and decreased gamma platelet growth rat
e, the net result of which was a retarded diffusional transformation kineti
cs of alpha to alpha/gamma lamellae. As a consequence of the microstructura
l changes, the high-temperature tensile properties and the creep properties
of the alloy were significantly improved. Anomalous hardening was also obs
erved at 800 degreesC, resulting in a tensile yield strength of 700 MPa. Th
e strengthening effect of carbon was realized by the microstructural refine
ment and by precipitation hardening of intergranular as well as interlamell
ar Ti3AlC. In terms of the tensile properties and the creep properties, the
optimum amount of carbon addition was 0.3 at. pct.