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Bimodal nanostructured (NS) metals composed of coarse-grained (CG) and nano-/ultrafine-grained phases possess high strength and good ductility. In this paper, three-dimensional (3D) microstructure-based numerical simulations via the mechanism-based strain gradient plasticity and the Johnson–Cook failure model are performed to study the effects of the shape and distribution of CG inclusions on the strength and ductility of bimodal NS Cu. Our results show that both the shape and distribution of CG inclusions significantly affect the overall ductility, while the former has more prominent influences than the latter. Spherical CG inclusions result in excellent overall ductility under all considered spatial distributions, while CG inclusions with sharp edges and corners facilitate microcrack initiation. However, the earlier microcrack initiation does not necessarily lead to a lower ductility since proper combinations of the shape and distribution of CG inclusions may retard microcrack propagation and thus enhance the overall ductility. These 3D microstructure-based simulations are helpful for the design of bimodal NS metals with improved mechanical properties. [ABSTRACT FROM AUTHOR]

Abstract: Visualization and representation of three-dimensional (3D) pore morphologies in the high-pressure die-cast Mg alloys are of significant interest for understanding and modeling processing–microstructure–properties relationships. In this contribution, an efficient and unbiased montage serial sectioning technique is applied for reconstruction of large volume (∼1.24×109 μm3) high-resolution (∼1μm) 3D microstructure of a high-pressure die-cast AM50 Mg alloy containing gas (air) and shrinkage pores. The reconstruction of 3D microstructure from montage serial sections enables visualization and characterization of detailed 3D morphologies and spatial correlations of gas (air) and shrinkage pores. The reconstructed 3D microstructure is implemented in a 3D finite elements (FE) computational framework to illustrate how realistic complex microstructural feature morphologies can be incorporated in the simulations of micromechanical response of these high-pressure die-cast cast microstructures. [Copyright &y& Elsevier]

A three-dimensional (3D) microstructure of Fe-intermetallic compounds (Fe-IMCs) was analyzed by means of x-ray tomography. 3D images were obtained to understand the internal structure of the Fe-IMCs in Al-Si-Mg-Fe alloys. A needle-shaped β phase appears in two-dimensional (2D) observations while platelet and irregular morphologies of the Fe-IMCs are identified in 3D investigations. The reconstructed microstructure was roughly crushed with 20% reduction rates and less broken parts of Fe-IMCs are observed, showing platelet and blunt morphologies. The combination of a large- and small-volume of the Fe-IMCs remained after a 60% reduction rate. The needle- and lateral-shaped of the Fe compounds were finely fragmented into the micro- and/or nano-scale at a 80% reduction rate. The average size of the Fe-IMCs is refined from 20.3 to 2.9 μm at the 80% reduction rate. The largest size of the Fe-IMCs is shortened from 85.5 to 21.3 μm. It is considered that fracture is affected by the length of the Fe-IMCs. Rapid cracks initiated around the fragmented Fe-IMCs at the reduction rate of 40% because the number of the Fe-IMCs is increased due to fragmentation. On the other hand, the harmful influence of Fe-IMCs on elongation becomes positive when the length of the Fe-IMCs decreases to less than a critical size. [ABSTRACT FROM AUTHOR]