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Abstract: The corrosion effects of 3.5% NaCl aqueous solution on the tensile mechanical, micromagnetic Barkhausen emission (MBE) and microfailure behavior of low carbon steel were investigated. At first it was found that this steel shows a dramatic and consistent decrease of its ductility with time of corrosion. The ductility reduction as well as microfailure features obtained by Scanning Electron Microscopy (SEM)-fractographic analysis yields an acceptable evidence for the occurrence of the Hydrogen Environmental Embrittlement (HEE) phenomenon during the corrosion process. During tensile straining the MBE-signal increases monotically at an average constant rate towards necking point. This rate shows tendency to increase with corrosion time fact which helped to establish the existence of a corrosion-induced micromagnetic hardening rate effect. It was shown that the main contribution to this effect should be attributed primarily to the combined effect of the HEE and dislocation multiplication and to a lower extent to the formed magnetite surface layers. Necking plasticity and MBE were correlated on the basis of combined stress bias and microvoid/microcracking-induced creation and rearangement of magnetic domains. [Copyright &y& Elsevier]

Abstract: A lattice Boltzmann model is proposed for the simulation of the statistical evolution of numerous microvoids under high stress triaxiality subjected to dynamic loadings. It considers the size distribution of microvoids during ductile fracture based on the balance law of microvoids’ number. A series of lattice Boltzmann equations governing the statistical evolution of microvoids are derived by using distribution function and multi-scale technique. Numerical results show that after a given time of evolution, microvoids in rate-sensitive materials are small and compact, whereas microvoids in rate-insensitive materials appear to be big and sparse, and the porosity in rate-insensitive material increases faster than that in rate-sensitive material. These numerical results might put insight into the mechanism of ductile fracture. [Copyright &y& Elsevier]

Abstract: Microstructure changes and micro-damage behaviors of a Al–6Mg alloy under the impact of GCr15 steel projectiles have been studied by optical microscope, scanning electron microscope (SEM) and transmission electron microscope (TEM). The results show that dynamic recrystallization in the material just adjacent to the crater can be induced by the hypervelocity impact. Dislocation cells formed during the impact process act as the nuclei of dynamic recrystallization, and the temperature rising caused by the heat transformed from the adiabatic plastic deformation work offers the temperature condition for the recrystallization. The degree of recrystallization depends on the impact velocity. Three kinds of micro-damages: micro-cracks, microvoids and adiabatic shear bands, in the region around the crater are usually produced by hypervelocity impacts. When the impact velocity is lower, grains within adiabatic shear bands are obviously fragmentated, and when the velocity is higher, whirlpool-like shear bands and wavy ones are formed just near the crater wall and the bottom, respectively. Micro-cracks are formed in front of the shear band, and are observed to propagate along the bands. Microvoids are observed in the region ahead of micro-cracks. [Copyright &y& Elsevier]