REDUCTION OF PRIMARY CREEP IN TIAL ALLOYS BY PRESTRAINING

The reduction of primary creep is important for TiAl alloys. In additi on to previous alloying and microstructure-controlling investigations, this study demonstrates that primary creep of TiAl alloy can also be significantly reduced by a prestraining technique. When the material w as first deformed at higher stresses for a few per cent strain, it did not begin to creep at a subsequent stress lower than a critical level , even after one week under load. This behaviour is in strong contrast to that exhibited by the material without prestraining under otherwis e identical conditions. The origin of this prestraining effect may ste m from the observed feature that creep of TiAl alloys is recovery-cont rolled at low stresses. The prestraining technique may be of technolog ical importance for prolonging the service life of a potential TiAl al loy component.