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| Dobrovská J., Hrbáček K., Dobrovská V., Stránský K., Dobrovský L. |
| STUDY OF NICKEL-BASED SUPERALLOY CHEMICAL MICROHETEROGENEITY |
Abstract
Nickel based alloys are characterised during crystallisation, similarly as carbon and alloyed steels, by an intensive dendritic segregation of constitutive elements and impurities, as well as admixtures. The process of dendritic segregation and its final state, which determines dendritic heterogeneity of the alloy under consideration, can be, nevertheless, described from the physical-metallurgical point of view with use of the same models that are used for steels. However, contrary to steels, segregation of which and final dendritic heterogeneity of which have been systematically investigated already for quite a long time (1? and we have thus at our disposal a comparatively large set of concrete data (partition coefficients of segregation elements, heterogeneity indexes and relationships between heterogeneity and properties of the relevant alloy), the number of such data for nickel based alloys is incomparably smaller (2?.
This work was aimed at investigation of chemical micro-heterogeneity of the nickel super-alloy IN 738 LC as cast and after long-term annealing at the temperature of 850°C. In order to achieve this goal we have used the original method of measurement of dendritic micro-heterogeneity of elements for the given nickel based alloy, and we have determined basic statistic parameters of heterogeneity of selected elements of the alloy. We have also determined effective partition coefficients both for the sample as cast and for the samples after long-term annealing.
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| Keywords: Ni-based superalloy|microsegregation|partition coefficients| |
| No 3 (2004), p. 209-218 |
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