Effect of Ti2AlC particles on the microstructure and elevated-temperature-deformation properties of gamma-TiAl alloys
Vpliv delcev Ti2AlC na mikrostrukturo in deformacijske lastnosti zlitin gama-TiAl pri povišani temperaturi

english

2014

volume 48, issue 6

titanium aluminides   mechanical properties    microstructure    carbides    carbon 

Inštitut za kovinske materiale in tehnologije
(Obvezni izvod spletne publikacije)

The g-TiAl intermetallics with and without amount fractions x = 0.3 % of yttrium and with different carbon amount fractions ranging from 0.9 % to 1.6 % were prepared by vacuum-induction melting in a graphite crucible. Different amounts of carbon were obtained by varying the time of melting. The resulting samples had large rod-like carbides with volume fractions 0.6 % to 3.7 % Ti2AlC in the lamellar matrix consisting of the alternating lamellas of g-TiAl and a2-Ti3Al phases. It was found that the grain size of the matrix decreases with the increasing volume fraction of Ti2AlC carbides from 430 %m to 35 %m. In addition, finer carbides with a similar composition were observed. Their size was below 1 %m and they appear mainly at the grain boundaries and also inside the lamellar grains. Compression testing revealed that all the samples had a relatively high yield strength at elevated temperature, from 917 MPa to 623 MPa at 600 °C and from 608 MPa to 547 MPa at 800 °C, but the best strength and the best yield strength were found for the sample with the lowest amount of the large rod-like Ti2AlC carbides. From these results it is concluded that the strengthening at an elevated temperature is a result of C in the solid solution and small carbide precipitates rather than of the rod-like Ti2AlC carbides.

06.11.2015