Federal University of São Carlos

About: Federal University of São Carlos is a education organization based out in São Carlos, Brazil. It is known for research contribution in the topics: Population & Microstructure. The organization has 16471 authors who have published 34057 publications receiving 456654 citations. The organization is also known as: UFSCar & Federal University of São Carlos.

A microstructural investigation of adiabatic shear bands in an interstitial free steel

Abstract: We report the microstructural characterization of induced adiabatic shear bands (ASB) in a hot-rolled interstitial free (IF) steel deformed at high strain rates (>2.8 × 104 s−1) in a split Hopkinson bar under controlled conditions at −50 and 25 °C. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) were used to reveal the degree of subdivision within ASB and neighboring grains. Deformation twins were found in adjacent grains suggesting that twinning occurs before the flow associated to shear banding. Progressive subgrain misorientation (PriSM) recrystallization is a plausible mechanism to explain the development of a new structure consisting of weakly textured ultrafine grains (0.1–0.5 μm) within the ASB. Recrystallization is proposed to occur by the formation and mechanical rotation of subgrains during deformation, coupled with boundary refinement via diffusion during shear band cooling. The presence of elongated subgrains and grains perfectly aligned within regions resembling a former lamellar structure within bands supports the occurrence of such a mechanism.

TEM and XRD study of early crystallization of lithium disilicate glasses

Abstract: Numerous researchers have speculated the precipitation of metastable phase(s) in the early stages of crystallization of lithium disilicate glass to explain the large discrepancies between the predictions of the classical nucleation theory (CNT) and experimental data. Therefore, we have investigated the early and intermediate stages of crystallization of three glasses on both sides of the stoichiometric composition through direct observations by transmission electron microscopy (TEM)/selected area electron diffraction (SAED) and X-ray diffraction (XRD). In samples heat-treated at ∼Tg=454 °C, two distinct crystalline phases, stable lithium disilicate (LS2) and metastable lithium metasilicate (LS) coexist up to 120 h at 454 °C (crystalline fraction