The effect of nickel on the martensitic-type transformations of Pt3Al and PtTi
- EDP Sciences
- Publication Type:
- Journal Article
- Journal de Physique IV France, 2001, 11 (Pr8), pp. 493 - 498
- Issue Date:
The effect of nickel on two classes of martensitic-type transformations in platinum systems has been studied. The first transformation is Ll to DO[c]' in the Pt3Al system and the second is B2 to B 19 in the TiPt system. The microstructures after transformation in the two systems are very different. The product of the PtAl transformation has a twinned microstructure, typical of cubic-to-tetragonal transformations. The product of the TiPt transformation is lath-like, although the morphology can be altered using heat treatments. The parent phase in the TiPt system is not retained at room temperature, whereas the parent phase in the PtAl transformation can be stabilised to room temperature. A great variation in hardness and transformation temperature is seen in each system as the composition is varied about the stoichiometric ratio, which has the lowest hardness. The PtAl transformation temperature has been reported to range from around room temperature to 1000°C. The TiPt transformation temperature can range from 1000 to 1080°C. The effect of nickel additions on these alloys also has a marked effect on the parent and product phase stability, and hence the microstructure and resulting hardness. The effect on the PtAl phase is complex, as nickel appears to stabilise the parent phase. The hardness varied in the region of 350 to 500 HV. For the TiPt phase, the hardness values were generally found to increase with the nickel additions increasing from 250 to about 600 HV. The addition of 20 at.% nickel decreases the transformation temperature from around 1000°C to about 600°C.
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