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.

中文翻译：

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谐波结构设计：结构材料优异机械性能的策略

结构化的异质材料在生物系统中无处不在，现在已被结构工程采用，以实现金属材料的定制性能。本文概述了称为谐波结构（HS）的独特网络类型的异质结构，该结构由一个连续的三维网络组成，该网络由坚固的超细晶粒（壳）骨架填充有柔软的粗晶粒（核心）区域的岛组成。HS的微观结构是通过战略性加工方法实现的，该方法涉及微米级金属粉末颗粒的严重塑性变形（SPD）及其随后的烧结。HS设计材料的微观结构和性能可通过根据材料的固有特性通过控制机械研磨和烧结条件来改变芯区和壳区的一部分来控制。HS设计的金属材料表现出高强度和延展性的出色组合，这归因于微结构基质中优化的分层特征。实验和数值结果表明，在塑性变形过程中，梯度结构的连续网络以及较大程度的微观结构异质性导致明显的机械不相容性和应变分配。因此，与传统的均质（均质）结构材料相反，在HS设计的材料中可以获得协同效应，例如协同增效。