Nanometer-scaled lamellar microstructures in Ti–45Al–7.5Nb–(0; 0.5)C alloys and their influence on hardness

In this study, nanometer-scaled lamellar microstructures were adjusted in Ti–45Al–7.5Nb–(0; 0.5C) alloys (in at.%) and analyzed by means of transmission electron microscopy. Different annealing temperatures subsequent to quenching were used to obtain well-defined lamellar microstructures with ultrafine widths of a few tens of nanometers to a few nanometers. Surprisingly, the hardness of these alloys is enhanced by increasing the volume fraction of γ-TiAl laths. This behavior is different from the results reported in literature and can be explained by the occurrence of a size effect. The nanometer-size γ laths became harder than the α2-Ti3Al laths which are 10 times wider.