Composition rules of Ni-base single crystal superalloys and its influence on creep properties via a cluster formula approach.

ABSTRACT: The present work investigated the composition evolution of the TMS series of Ni-base single crystal (SC) superalloys in light of the cluster formula approach systematically. The cluster formula of SC superalloys could be expressed with [Formula: see text], in which all the alloying elements were classified into three groups, Al series ([Formula: see text]), Cr series ([Formula: see text]), and Ni series ([Formula: see text]). It was found that the total atom number (Z) of the cluster formula units for TMS series of superalloys varies from Z?~?17 to Z?~?15.5, and then to Z?~?16 with the alloy development from the 1st to the 6th generation, in which the superalloys with prominent creep resistance possess an ideal cluster formula of [Formula: see text] with Z?=?16. Similar tendency of composition evolution also appears in the PWA and CMSX series of SC superalloys. Typical TMS series of superalloys with prominent creep properties generally exhibit a moderate lattice misfit of ?/?' which could render alloys with appropriate particle size of cuboidal ?' precipitates to acquire a maximum strength increment by precipitation strengthening mechanism. More importantly, the relationship between the lattice misfit (?) of ?/?' and the creep rupture lifetime (t_r) of superalloys was then established, showing a linear correlation in the form of lgt_r-lg|?|^3/2 at both conditions of 900 °C/392 MPa and 1100 °C/137 MPa. Combined with the lattice misfit, the cluster formula approach would provide a new way to modify or optimize the compositions of Ni-base superalloys for further improvement of creep property.

SUBMITTER: Chen C 

PROVIDER: S-EPMC7728759 | biostudies-literature | 2020 Dec

REPOSITORIES: biostudies-literature