Depletion and voids formation in the substrate during high temperature oxidation of Ni-Cr alloys

A numerical model to treat the kinetics of vacancy annihilation at the metal/oxide interface but also in the bulk metal has been implemented. This was done using EKINOX, which is a mesoscopic scale 1D-code that simulates oxide growth kinetics with explicit calculation of vacancy fluxes. Calculations were performed for high temperature Ni-Cr alloys oxidation forming a single chromia scale. The kinetic parameters used to describe the diffusion in the alloy were directly derived from an atomistic model. Our results showed that the Cr depletion profile can be strongly affected by the cold work state of the alloy. In fact, the oversaturation of vacancies is directly linked to the efficiency of the sinks which is proportional to the density of dislocations. The resulting vacancy profile highlights a supersaturation of vacancy within the metal. Based on the classical nucleation theory, the possibility and the rate of void formation are discussed

Palaeo-environmental observations on the ancient Holocene of the Florentine area

Ricostruzione paleoambientale nell'area di Firenze

The Bell Beaker Tumulus on Via Bruschi in Sesto Fiorentino: new researches

The archaeological area of Via Bruschi, already noted for some twenty years as a centre of ritual (Sarti et al. 1987-1988), is among the settlement evidence for Developed Bell Beaker Step 3 (Leonini, Sarti 2008). The study of Bell Beaker settlements in the Florentine area has been carried out through analysis of their relationship to the landscape of the past, by attempting to reconstruct its settings and its sequence of changes identified at a local level. The analysis of the spatial, chronological and functional relationships of the settlement and ritual findings (rendered interactive and dynamic by use of GIS) must, in fact, include the evaluation of the presumed relationships and contacts between the excavated structures. These relationships are not identifiable, at the present time, in a direct way because of the limitations of field research. For this reason, a hypothesis already proposed earlier (Sarti, Martini 2001) has been confirmed for two Bell Beaker areas. Furthermore, it is valid in general on a territorial scale (Pizziolo, Sarti 2006) or where it is possible to apply the concept of “Settlement Unit” (Pizziolo, Sarti 2008). This concept refers to a large context, within which different structural finds can be recognized, belonging to different phases during which the same space was in use. It includes large settlement nuclei (Settlement Units), with functional structures and substructures, all of long duration with the re-use of areas in the close vicinity; Via Bruschi is related to a group of two large settlement areas, Sassaiola and Frilli, referred to as Developed Bell Beaker