Hostname: page-component-848d4c4894-89wxm Total loading time: 0 Render date: 2024-07-06T18:47:13.626Z Has data issue: false hasContentIssue false

Precipitation Phenomena and Strain Hardening of Intermetallic Titanium Aluminides

Published online by Cambridge University Press:  11 February 2011

J. Müllauer
Affiliation:
Institute for Materials Research, GKSS Research Center, Max-Planck-Strasse, D-21502 Geesthacht, Germany
F. Appel
Affiliation:
Institute for Materials Research, GKSS Research Center, Max-Planck-Strasse, D-21502 Geesthacht, Germany
Get access

Abstract

In two-phase titanium aluminide alloys, the implementation of precipitation reactions is a widely utilized concept to control the microstructure and strengthen the material. A study has been made on the influence of carbide and boride precipitates on dislocation mobility and strengthening at 300 K. Compression tests were carried out for characterizing the mechanisms determining flow stress and dislocation glide resistance. The interaction mechanisms between the precipitates and dislocations were assessed by thermodynamic glide parameters and transmission electron microscopy. It has been shown that small titanium boride precipitates and carbide precipitates of perovskite type act as long-range dislocation glide obstacles. The interaction between the dislocations and the borides and carbides mainly leads to an athermal stress contribution. However, the dislocation-particle interactions are quite different. Small groups of borides are encircled by dislocations. This gives rise to the formation of loop structures the density of which increases with strain. On the contrary, the carbide precipitates are shearable and can be overcome without Orowan looping. This different behaviour is also reflected in the work hardening characteristics. Whereas the work hardening coefficient of the boron doped material increases with increasing B-concentration, it is independent of concentration in the case of the carbon-doped material.

Type
Research Article
Copyright
Copyright © Materials Research Society 2003

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

[1] Kim, Y-W., JOM 41 (1991), 24.Google Scholar
[2] Appel, F. and Wagner, R., Mater. Sci. Eng. (1998), R22, 187.Google Scholar
[3] Appel, F., Brossmann, U., Christoph, U., Eggert, St., Janschek, P., Lorenz, U., Müllauer, J., Oehring, M., and Paul, J.D.H., Adv. Eng. Mater. (2000), 2, No. 11, 699.Google Scholar
[4] Larsen, D. E., Mater. Res. Soc. Symp. Proc. (1990),Vol. 194, 285.Google Scholar
[5] Christoph, U., Appel, F., Wagner, R., Mater. Sci. Eng. A 239–240, (1997) 39.Google Scholar
[6] Appel, F., Sparka, U., Wagner, R., Intermetallics 7, (1999) 325.Google Scholar
[7] Tian, W. H. and Nemoto, M., in Gamma Titanium Aluminides, (eds. Kim, Y.-W., Wagner, R. and Yamaguchi, M.) TMS, Warrendale, PA, (1995), 689.Google Scholar