Microsegregations of alloying elements developed during solidification are known to affect solid state transformations in spheroidal graphite cast irons. However, no clear relation between them and the presence and extension of ferrite halos has been established until now. The aim of the present work is to expose how the microsegregations of Si, Mn and Cu influence in the transition from stable to metastable system during solid state transformations and how the extension of the ferrite halo is affected accordingly. The study was carried out on samples cast at a cooling rate of 20 K/min, which allowed the diffusion of carbon under equilibrium conditions.

This investigation studies the partitioning of Mn and Cu – and Si– between ferrite and cementite in the pearlite of two alloys containing similar Mn and Si concentrations, but different Cu contents, keeping the Cu concentration within the usual industrial limits. The results confirm the partitioning of all the elements between ferrite and cementite during pearlite growth. Furthermore, the presence of nanometric Cu-rich precipitates was detected for an alloy with typical Cu contents for achieving pearlitic structures in spheroidal graphite cast irons. This might be linked to the microsegregation of Cu developed during the solidification step. These precipitates have not been reported before and cannot be ignored as they can affect the transformation kinetics and the mechanical properties of the alloy.

Meteorites carry information about the most common processes that have been active in the early solar system. In particular, mesosiderites are meteorites with a structure considered to be composed of equal parts of iron–nickel metal and silicates. A natural delimitation in the study of such complex systems is the discrimination of the iron–nickel metallic and silicate domains. In this work, we focus on the metallic phases of the Mincy mesosiderite, a specimen available at the Instituto de Ciencias Astronómicas, de la Tierray y del Espacio repository. In Mincy, the metallic phases are iron–nickel–carbon alloys that are distributed forming metallic lumps or pebbles (referred to as metallic nodules in the article) in which kamacite and taenite are present, and taenite is found both at the kamacite/silicate interface and surrounded by kamacite, that is, isolated from the silicates. We made use of the electron backscattered diffraction technique to determine the crystallographic orientation relationships along the taenite/kamacite boundaries as well as for characterizing the (hkl)‐specific grain boundaries regarding the underlying tilt, twist, or twinning mechanism to assist the interpretation of the phase transformations and mechanisms that could explain the formation of these metallic nodules. From the results, each of the metallic nodules has a unique temperature–pressure history and kinetics to undergo phase transformations (mainly partial melting, heterogeneous nucleation‐controlled solidification, and possible evaporation–condensation) as well as liquid‐phase sintering and recrystallization in its own way.