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Abstract: A three-dimensional numerical analysis of the mesoscale deformation behavior of welded low-carbon steel specimens is performed. A weld-affected polycrystalline microstructure is designed to reproduce gradual changes of the grain size throughout the base metal and heat-affected zone regions. A mathematical model based on a double-limit yield criterion is used to describe Lüders band propagation characteristic of this type of steel. The effects of the free surface, grain boundaries and interfaces between the fusion zone and the heat-affected zone, and between the heat-affected zone and the base metal are discussed. [Copyright &y& Elsevier]

Abstract: Classical molecular dynamics simulations of the interaction of edge dislocations in Ni with chains of spherical Ni3Al precipitates are performed using EAM potentials. The order hardening is investigated at temperature  K by determining the critical resolved shear stresses (CRSSs) for a superdislocation that is dissociated into four partial dislocations. The CRSS is computed as a function of the radius and the distance of the precipitates. It is found that for precipitates with a diameter smaller than the dissociation width of perfect edge dislocation in Ni, the CRSS of the trailing dislocation of the superdislocation is a fraction of about 0.4 of the CRSS of the leading dislocation. [Copyright &y& Elsevier]

The creep behavior of HR3C austenitic steels was investigated at 650 °C and over the stress range from 150 to 250 MPa for up to 13,730 h. The corresponding microstructure evolution was characterized by optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In the initial stage of the creep process, the creep-resistance of HR3C steel is enhanced by the precipitation of second-phases particles in the grain and at the grain boundary. Compared with the precipitates inside the grain, the higher nucleation and growth rate of precipitates at the grain boundary is related to the higher interfacial energy and diffusion rate of atoms. The high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) results show that the precipitates inside the grain may initially nucleate at dislocation pile-up sites, and the interface coherency between the precipitate and the matrix can be destroyed after a long-term creep process. The TEM morphology indicates that the agglomerated tiny particles interact with the dislocations, contributing mostly to the precipitation strengthening inside the grain during the long-term creep process at 650 °C, while the growth of chain-like M 23 C 6 precipitates at the grain boundary increases the tendency of intergranular cracking as the creep time increased. [ABSTRACT FROM AUTHOR]