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Metal additive manufacturing (AM) technologies have made significant progress in the basic theoretical field since their invention in the 1970s. However, performance instability during continuous processing, such as thermal history, residual stress accumulation, and columnar grain epitaxial growth, consistently hinders their broad application in standardized industrial production. To overcome these challenges, performance-control-oriented hybrid AM (HAM) technologies have been introduced. These technologies, by leveraging external auxiliary processes, aim to regulate microstructural evolution and mechanical properties during metal AM. This paper provides a systematic and detailed review of performance-control-oriented HAM technology, which is categorized into two main groups: energy field-assisted AM (EFed AM, e.g. ultrasonic, electromagnetic, and heat) technologies and interlayer plastic deformation-assisted AM (IPDed AM, e.g. laser shock peening, rolling, ultrasonic peening, and friction stir process) technologies. This review covers the influence of external energy fields on the melting, flow, and solidification behavior of materials, and the regulatory effects of interlayer plastic deformation on grain refinement, nucleation, and recrystallization. Furthermore, the role of performance-control-oriented HAM technologies in managing residual stress conversion, metallurgical defect closure, mechanical property improvement, and anisotropy regulation is thoroughly reviewed and discussed. The review concludes with an analysis of future development trends in EFed AM and IPDed AM technologies. Performance-control-oriented hybrid additive manufacturing was defined as the review scope. Multifarious technologies were classified, summarized and synthesized based on applied objects. Microstructural evolution, mechanical property, and defect elimination were depicted and compared. The synergetic enhancement of strength and ductility was statistically measured and analyzed. Future development trends were predicted on account of the historical outline and research status.

The present overview gives a new approach toward developments and recent achievements in severe plastic deformation. The review focuses on several subjects. First, an outline of SPD research status in the world is presented by literature analysis based on the total number of publications, citations, and the contribution of the top-ranked countries. Second, the mechanisms of grain refinement and grain growth during SPD processing are discussed by means of the latest concepts. Third, all SPD methods invented so far are classified based on a new approach. Up to now, the growing tendency of researchers to introduce new SPD techniques results in a large number of SPD methods which can be considered as new or modified techniques or a combination of previous ones. Such a reference can help to prevent the future duplication to introduce the SPD processes, which are technically similar. At the end, the practical applications of ultrafine/nanostructured materials and industrial commercialization of SPD methods are summarized.

Understanding the direct effects of hydrogen bonding (H‐bonding) on the mechanical response of glassy state polymers remains a challenge, largely owing to the use of semicrystalline polymers in such studies, wherein, separating the contributions due to the changes in degree of crystallinity and direct H‐bonding effects on the observed mechanical properties is extremely difficult. This limitation is overcome by studying the mechanical behavior of amorphous, glassy polyvinylpyrrolidone (PVP), H‐bonded with tannic acid (TA). Uniaxial tension experiments on individual submicron scale PVP fibers (0.6–1.0 µm diameters) with different TA concentrations are conducted to capture their elasto‐plastic deformation characteristics. Amorphous PVP‐TA complexes exhibited some distinctive trends in elasto‐plastic properties with increasing H‐bond density, which are not observed earlier. These distinctive trends are discussed in terms of the competing effects of H‐bond driven crosslinking and TA‐induced reduction in entanglement density, and their differing roles during elastic and plastic deformation. The improvements in elasto‐plastic properties (particularly ductility and toughness) are simultaneously accompanied by uniquely significant thermal stability (i.e., glass transition temperature, Tg) improvements, that can help improve the practical applicability, operational life, and performance of these materials. H‐bonding is shown to significantly improve the mechanical properties of an already strong, tough, and glassy polymer, PVP, in the nanofiber form. It is shown that properties like strength, toughness, and thermal stability, which are commonly considered orthogonal, can all be simultaneously improved, thus opening new material design spaces for advanced applications.

Nanoindentation testing using a Berkovich indenter was conducted to explore the relationships among indentation hardness (H), elastic work energy (We), plastic work energy (Wp), and total energy (Wt = We + Wp) for deformation among a wide range of pure metal and alloy samples with different hardness, including iron, steel, austenitic stainless steel (H ≈ 2600–9000 MPa), high purity copper, single-crystal tungsten, and 55Ni–45Ti (mass%) alloy. Similar to previous studies, We/Wt and Wp/Wt showed positive and negative linear relationships with elastic strain resistance (H/Er), respectively, where Er is the reduced Young’s modulus obtained by using the nanoindentation. It is typically considered that Wp has no relationship with We; however, we found that Wp/We correlated well with H/Er for all the studied materials. With increasing H/Er, the curve converged toward Wp/We = 1, because the Gibbs free energy should not become negative when indents remain after the indentation. Moreover, H/Er must be less than or equal to 0.08. Thermodynamic analyses emphasized the physical meaning of hardness obtained by nanoindentation; that is, when Er is identical, harder materials show smaller values of Wp/We than those of softer ones during nanoindentation under the same applied load. This fundamental knowledge will be useful for identifying and developing metallic materials with an adequate balance of elastic and plastic energies depending on the application (such as construction or medical equipment).

In this review, severe plastic deformation (SPD) is considered as a materials processing technology. The deformation mode is the principal characteristic differentiating SPD techniques from common forming operations. For large plastic strains, deformation mode depends on the distribution of strain rates between continuum slip lines and can be varied from pure shear to simple shear. A scalar, invariant, and dimensionless coefficient of deformation mode is introduced as a normalized speed of rigid rotation. On this basis, simple shear provides the optimal mode for structure modification and grain refinement, whereas pure shear is “ideal” for forming operations. Special experiments and SPD practice confirm this conclusion. Various techniques of SPD are classified and described in accordance with simple shear realization or approximation. It is shown that correct analyses of the processing mechanics and technological parameters are essential for the comparison of SPD techniques and the development of effective industrial technologies.

The influence of the nanocrystalline structure produced by severe plastic deformation (SPD) on the corrosion behavior of CoCrFeMnNi alloys with Cr contents ranging from 0 to 20 at.% was investigated in aqueous 0.5 M H2SO4 and 3.5% NaCl solutions. The resistance to general corrosion and pitting became higher in both the solutions, with higher passivation capability observed with increasing Cr content, and it is believed that the high corrosion resistance of CoCrFeMnNi alloys can be attributed to the incorporation of the Cr element. However, the impact of the nanocrystalline structure produced by SPD on the corrosion behavior was negligibly small. This is inconsistent with reports on nanocrystalline binary Fe–Cr alloys and stainless steels processed by SPD, where grain refinement by SPD results in higher corrosion resistance. The small change in the corrosion behavior with respect to grain refinement is discussed, based on the passivation process of Fe–Cr alloys and on the influence of the core effects of HEAs on the passivation process.

There has been a great interest in evaluating the potential of severe plastic deformation (SPD) to improve the performance of magnesium for biological applications. However, different properties and trends, including some contradictions, have been reported. The present study critically reviews the structural features, mechanical properties, corrosion behavior and biological response of magnesium and its alloys processed by SPD, with an emphasis on equal-channel angular pressing (ECAP) and high-pressure torsion (HPT). The unique mechanism of grain refinement in magnesium processed via ECAP causes a large scatter in the final structure, and these microstructural differences can affect the properties and produce difficulties in establishing trends. However, the recent advances in ECAP processing and the increased availability of data from samples produced via HPT clarify that grain refinement can indeed improve the mechanical properties and corrosion resistance without compromising the biological response. It is shown that processing via SPD has great potential for improving the performance of magnesium for biological applications.

Fatigue is a dominant failure mechanism of several engineering components. One technique for increasing the fatigue life is by inducing surface residual stress to inhibit crack initiation. In this review, a microstructural study under various bulk (such as severe plastic deformation) and surface mechanical treatments is detailed. The effect of individual microstructural feature, residual stress, and strain hardening on mechanical properties and fatigue crack mechanisms are discussed in detail with a focus on nickel-based superalloys. Attention is given to the gradient microstructure and interface boundary behavior for the mechanical performance. It is recommended that hybrid processes, such as shot peening (SP) followed by deep cold rolling (DCR), could enhance fatigue life. The technical and scientific understanding of microstructural features delineated here could be useful for developing materials for fatigue performance.

Severe plastic deformation (SPD) is effective in producing bulk ultrafine-grained and nanostructured materials with large densities of lattice defects. This field, also known as NanoSPD, experienced a significant progress within the past two decades. Beside classic SPD methods such as high-pressure torsion, equal-channel angular pressing, accumulative roll-bonding, twist extrusion, and multi-directional forging, various continuous techniques were introduced to produce upscaled samples. Moreover, numerous alloys, glasses, semiconductors, ceramics, polymers, and their composites were processed. The SPD methods were used to synthesize new materials or to stabilize metastable phases with advanced mechanical and functional properties. High strength combined with high ductility, low/room-temperature superplasticity, creep resistance, hydrogen storage, photocatalytic hydrogen production, photocatalytic CO 2 conversion, superconductivity, thermoelectric performance, radiation resistance, corrosion resistance, and biocompatibility are some highlighted properties of SPD-processed materials. This article reviews recent advances in the NanoSPD field and provides a brief history regarding its progress from the ancient times to modernity. Abbreviations: ARB: Accumulative Roll-Bonding; BCC: Body-Centered Cubic; DAC: Diamond Anvil Cell; EBSD: Electron Backscatter Diffraction; ECAP: Equal-Channel Angular Pressing (Extrusion); FCC: Face-Centered Cubic; FEM: Finite Element Method; FSP: Friction Stir Processing; HCP: Hexagonal Close-Packed; HPT: High-Pressure Torsion; HPTT: High-Pressure Tube Twisting; MDF: Multi-Directional (-Axial) Forging; NanoSPD: Nanomaterials by Severe Plastic Deformation; SDAC: Shear (Rotational) Diamond Anvil Cell; SEM: Scanning Electron Microscopy; SMAT: Surface Mechanical Attrition Treatment; SPD: Severe Plastic Deformation; TE: Twist Extrusion; TEM: Transmission Electron Microscopy; UFG: Ultrafine Grained This article comprehensively reviews recent advances on development of ultrafine-grained and nanostructured materials by severe plastic deformation and provides a brief history regarding the progress of this field.

Fusion welding causes joint deterioration when joining aluminum alloys, which limits the use of aluminum alloy components in high-end equipment. This paper focuses on an overview of how to achieve high-strength aluminum alloy welded joints using welding/plastic deformation composite forming technology. The current technology is summarized into two categories: plastic deformation welding and plastic deformation strengthening. Plastic deformation welding includes friction stir welding, friction welding, diffusion welding, superplastic solid-state welding, explosive welding, and electromagnetic pulse welding. Plastic deformation strengthening refers to the application of plastic deformation to the weld seam or heat-affected zone, or even the whole joint, after welding or during welding, including physical surface modification and large-scale plastic deformation technology. Important processing parameters of plastic deformation welding and their effects on weld quality are discussed, and the microstructure is described. The effect of plastic deformation strengthening technology on the microstructure and performance evolution, including the hardness, tensile strength, fatigue property, residual stress, and hot cracking of aluminum alloy welded joints, and its evolution mechanism are systematically analyzed. Finally, this paper discusses the future development of plastic deformation strengthening technology and anticipates growing interest in this research area.