Superior ductility in magnesium alloy-based nanocomposites: the crucial role of texture induced by nanoparticles

In an expansive field of metals, magnesium has been trending of late in automobile, aerospace, defense, sports, electronic and biomedical sectors as it offers an advantage in lightweighting. In the realm of Mg-based materials, Mg nanocomposites have a good combination of specific strength, thermal and damping properties, but lack a high ductility and do not typically undergo a large amount of uniform elongation. The current work bridges this gap by reporting a magnesium nanocomposite (Mg�1.8Y/1.5Y 2 O 3 ) that exhibits a significantly high tensile ductility of 36. Microstructural characterization of the nanocomposite revealed that the striking presence of micron-Mg�Y phases and nano-Y 2 O 3 particles in matrix led to a bimodal particle distribution which affected the dynamic recrystallization mechanism. It was also observed that the addition of Y 2 O 3 nanoparticles weakened the texture of nanocomposite. The dominating influence of texture weakening over other mechanisms (grain refinement and alleviated micro-strain) on the plastic deformation/ductility of the nanocomposite is highlighted, and the contribution of nanoparticles toward the enhancement of ductility is ascertained. In contrast to the previous studies where Mg-based nanocomposites are known to have improved strengths, this approach can be used to develop magnesium nanocomposites that are exceptional. © 2019, Springer Science+Business Media, LLC, part of Springer Nature

Surface mechanical attrition treatment of additively manufactured 316L stainless steel yields gradient nanostructure with superior strength and ductility

Abstract Surface severe plastic deformation (S²PD) of additively manufactured/three-dimensional (3D) printed metallic parts is gaining increased attention as a post-manufacturing operation to enhance the material performance in a wide variety of applications. Surface mechanical attrition treatment (SMAT) is an S²PD technique that can yield a nanostructured surface layer induced by compressive stresses and work hardening. In the present study, SMAT was performed on 316L (austenitic) stainless steel (SS) processed by selective laser melting (SLM), and the consequent effects on mechanical response were investigated. The underlying mechanisms of microstructural evolution leading to the formation of nanocrystalline grains resulting from SMAT in SLM 316L SS are elucidated. The interactions between twins and deformation bands act as potential sites for impeding the movement of dislocations, which in turn leads to the formation of stacking faults, twinning, and occasionally transform to a different crystal structure. Twin-twin and/or twin-deformation band intersections sub-divide the matrix grains into smaller cells or low-angle disoriented blocks, which result in the formation of low-angle grain boundaries and finally in nanocrystallization at the surface. The size of nanocrystalline grains increases progressively with depth from the surface to micrometer size grains in bulk. The gradient nanostructure in the additively manufactured alloy after SMAT imparts an unusual combination of strength and ductility that markedly exceeds that of conventional, bulk nanostructured, or even high-performance 316L SS (containing nanoscale deformation twins embedded in submicron-sized austenitic grains obtained by dynamic plastic deformation processes). Analytical models revealed that strengthening results from a combination of grain boundaries and dislocations. The results of the present investigation pave the way for engineering high-performance SS for a variety of engineering applications

A strong and deformable in-situ magnesium nanocomposite igniting above 1000 °c

10.1038/s41598-018-25527-0Scientific Reports81703