Abstract
Structured heterogeneous materials are ubiquitous in a biological system and are now adopted in structural engineering to achieve tailor-made properties in metallic materials. The present paper is an overview of the unique network type heterogeneous structure called Harmonic Structure (HS) consisting of a continuous three-dimensional network of strong ultrafine-grained (shell) skeleton filled with islands of soft coarse-grained (core) zones. The HS microstructure is realized by the strategic processing method involving severe plastic deformation (SPD) of micron-sized metallic powder particles and their subsequent sintering. The microstructure and properties of HS-designed materials can be controlled by altering a fraction of core and shell zones by controlling mechanical milling and sintering conditions depending on the inherent characteristics of a material. The HS-designed metallic materials exhibit an exceptional combination of high strength and ductility, resulting from optimized hierarchical features in the microstructure matrix. The experimental and numerical results demonstrate that the continuous network of gradient structure in addition to the large degree of microstructural heterogeneity leads to obvious mechanical incompatibility and strain partitioning, during plastic deformation. Therefore, in contrast to the conventional homogeneous (homo) structured materials, synergy effects, such as synergy strengthening, can be obtained in HS-designed materials. This review highlights recent developments in HS-structured materials as well as identifies further challenges and opportunities.
Highlights
IntroductionMetallic materials are significantly crucial for manufacturing industry and structural applications
Metallic materials are significantly crucial for manufacturing industry and structural applications.Metals with an optimized balance of higher strength and ductility are in demand for many industrial applications
The harmonic structure (HS)-designed metallic materials can be successfully produced by efficient powder metallurgy approaches, such as mechanical milling and bimodal milling (BiM)
Summary
Metallic materials are significantly crucial for manufacturing industry and structural applications. The focus of this review is, on microstructures and improve the mechanical properties through grain refinement by several means, single-phase metallic materials, such as; pure metals (Ti and Ni) or solid solutions (SUS316L) based for example; severe plastic deformation, thermo-mechanical treatments, friction stir processing, etc These techniques use the interruption in the dislocations’ motion, but still make a dislocation activity possible ensure some ductility. 1 depicts a schematic of aHowever, true stress–true by introducing heterogeneities in the microstructure matrix, the strain hardening rate dσ/dε of the strain diagram of conventional homo-structured metallic materials. The localized reduction in the cross-sectional area of the tensile specimen, i.e., words, a good combination of superior strength and ductility can be achieved when a larger strain necking, occurs when the rate of strain hardening is lower than the flow stress of the material. An overview of the basics of harmonic structure design and highlighting recent developments in harmonic structured materials is presented, as well as identifying perspectives and future challenges and opportunities
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