Microstructural Characterization of Graphite Spheroids in Ductile Iron

The present work brings new insights by transmission electron microscopy allowing disregarding or supporting some of the models proposed for spheroidal growth of graphite in cast irons. Nodules consist of sectors made of graphite plates elongated along a hai direction and stack on each other with their c axis aligned with the radial direction. These plates are the elementary units for spheroidal growth and a calculation supports the idea that new units continuously nucleate at the ledge between sectors

NLL′{'} resummation of jet mass

Starting from a factorization theorem in effective field theory, we present resummed results for two non-global observables: the invariant-mass distribution of jets and the energy distribution outside jets. Our results include the full next-to-leading-order corrections to the hard, jet and soft functions and are implemented in a parton-shower framework which generates the renormalization-group running in the effective theory. The inclusion of these matching corrections leads to an improved description of the data and reduced theoretical uncertainties. They will have to be combined with two-loop running in the future, but our results are an important first step towards the higher-logarithmic resummation of non-global observables.Comment: 32 pages, 12 figures. v2: journal versio

Effect of Ce and Sb on Primary Graphite Growth in Cast Irons

It is well-known that if certain trace elements are present in cast iron melts the morphology of the graphite precipitates can be altered. In order to understand the effect of doping elements on primary growth of graphite, pure Fe–Sb alloys were prepared by induction melting. They were then placed in graphite crucibles and heated to a temperature above the Fe–C eutectic so that the charge became saturated in carbon and melted. To obtain Fe–Ce alloys, metallic Ce was added at the bottom of a graphite crucible and covered with iron, and then heated as for the Fe–Sb charge. In both cases, the melt was then cooled and held slightly above the eutectic temperature so that primary graphite crystals, which had nucleated on the crucible walls and then detached from it, could grow freely in the melt. The influence of the added elements on graphite growth was revealed by the change in the shape and distribution of the crystals compared to those obtained in similar experiments carried out with pure Fe. The experiments were made in air and vacuum so as to point out possible interactions between the elements present in the melt and oxygen

Examination of Austenite Solidification and Spheroidal Graphite Growth in Ni-Fe-C Alloys

The austenite phase and the spheroidal graphite in a Ni-Fe-C alloy at various solidification stages were captured by quenching experiments using spherical ceramic shell molds with inserted thermocouples. Multiple graphite nodules/spheroidal graphite particles inside an eutectic cell were observed using optical microscopy. Individual eutectic cells were differentiated by an intermetallic phase occurring within the interdendritic regions. Electron backscatter diffraction (EBSD) and orientation image mapping (OIM) analyses were performed to investigate the crystallographic orientation and the grain boundary distribution of the austenite grains surrounding individual spheroidal graphite particles. The austenite engulfment process around the spheroidal graphite was revealed by EBSD/OIM analyses. Examination of the graphite nodules extracted by deep etching experiments revealed three stages of growth for the spheroidal graphite particles