Creep cavitation in 304 stainless steel

Abstract

A micromechanical analysis of deformation and fracture in creeping alloys is presented based on a mechanistic approach using continuum mechanics. The analysis was first carried out on a coarse microscopic level in which the self-consistent theory of Hill was employed to treat the steady state creep of heterogeneous alloys with coarse microstructures allowing for grain boundary sliding. Processes operating on a finer scale than the grain size such as grain boundary diffusion and surface diffusion were subsequently included in the analysis. It was found that the high stresses required for cavity nucleation occur at intergranular particles only in transients of grain boundary sliding, and that two modes of cavity growth result corresponding to rate control by each of the abovementioned diffusional processes.Creep cavitation in 304 stainless steel in the neighborhood of 0.5 Tm was studied experimentally to test these theoretical models. Our results suggest that a broad spectrum of interfacial energy may exist and that microstructural changes such as those caused by twins can alter cavitation behavior drastically. Cavities grow in most cases by grain boundary diffusion coupled with matrix creep, somewhat restricted by surface diffusion. However, the grain boundary sliding can be a dominant mode of cavity growth at high stresses and for large cavities.

Interaction of cavitating grain boundary facets in creeping polycrystals

“…Clearly, the representation of grain boundary cavities in terms of a continuous variation of 6c over a grain boundary facet, presumes that the cavity spacing is significantly smaller than the facet length. This is a reasonable approximation for many metals, as has been shown experimentally by micrographs of polished sections (Hull and Rimmer, 1959;Ashby and Dyson, 1984;Riedel, 1985;Saxena and Bassani, 1984) or by SEM showing fine dimples left by cavities on intergranular fracture surfaces (Chen and Argon, 1981;Dyson and Loveday, 1980). Experimental observations of cavity nucleation (Dyson, 1983;Argon, 1982) show that the number of cavities grows continuously, mainly as a function of the effective strain.…”

A creep rupture model accounting for cavitation at sliding grain boundaries

“…1 a will be accompanied by a noticeable amount of sliding, unless the viscosity i s in (2 .4) is relatively large . Diffusional growth accompanied by grain boundary sliding may give rise to non-equilibrium void shapes showing inversion symmetry, as discussed by Argon and Chen [3,22,23], and may give an important contribution to accelerated cavity growth in the last stage of creep (see [23]) . A first quantitative model of diffusive cavity growth on sliding grain boundaries was introduced recently by Chen [24] .…”

Autonomous Repair Mechanism of Creep Damage in Fe-Au and Fe-Au-B-N Alloys

“…[1,2] Extensive research has focussed on identifying the metallurgical processes that help preventing the formation of this pore-related high-temperature creep damage. [3][4][5] A viable alternative to these established approaches to avoid premature creep damage can be achieved by incorporation self-healing capabilities in these steels. As recently demonstrated, self-healing of damage can significantly enhance the component lifetime for a wide range of materials, including metals.…”