1992    
1993    
1994    
1995    
1996    
1997    
1998    
1999    
2000    
2001    
2002    
2003    
2004    
2005    
2006    
2007    
2008    
2009    
2010    
2011    
2012    
2013    
2014    
2015    
2016    
Häußler, D., Messerschmidt, U., Bartsch, M., Appel, F., Wagner, R.

In situ high-voltage electron microscope deformation study on a two-phase( a2+g) TiAl alloy
Materials Science & Engineering A 233, pp 15-25 (1997)
In situ straining experiments in a high-voltage electron microscope have been performed on two-phase Ti-47at.%Al-2at.Cr-0.2at.%Si at room temperature and at 900 K. Two microstructures were investigated which were produced by thermomechanical treatments: a so-called near-gamma and a nearly lamellar microstructure. The processes controlling the motion of individual dislocations in the phase are very similar in both materials. At room temperature, ordinary dislocations and superdislocations show a jerky motion which is impeded by localized obstacles and jogs. At high temperature, the dislocations are smoothly bent or arranged in preferred orientations and move in a viscous way. This mode of motions as well as the nonplanar arrangement of dislocations point to the action of climb as an essential process during the high-temperature deformation of Ti-Al. These observations are very similar to those on Al-rich single phase TiAl investigated earlier. The considerably higher flow stress of the two-phase alloys is an effect of their particular microstructures, i.e. of grain boundaries and lamella interfaces.

ki-1997-i02