Mechanical properties of the alloy 36NKhTYu in relation to the mechanisms underlying the precipitation of the γ′-and η-phases

The kinetic characteristics of processes taking place during the aging of the alloy 36NKhTYu at 700–850?C were studied; these included an increase in the diameter of theγ′-phase particles formed in regions of continuous decomposition, an increase in the thickness of theγ′-lamellas formed in regions of discontinuous decomposition, and an increase in the volumetric proportion of material in which continuous precipitation of theγ′-phase was occurring. The formation of theη-phase was also studied (the degree of discontinuous precipitation of theη-phase depended on the quench temperature); interstitial stacking faults appeared, their formation and growth being associated with the precipitation of titanium carbide. With increasing period of aging the mechanism underlying the interaction of the dislocations with theγ′-particles changed; initially the particles were intersected by superdislocations; later they were encircled by single dislocations. The discontinuousγ′-phase precipitation which occurred on aging the material after quenching from 1280?C (in the case of fine-grained samples) was ascribed to the fact that insufficient carbon was available to provide carbide particles for pinning the grain boundaries.