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1. An Overview on the Effect of Severe Plastic Deformation on the Performance of Magnesium for Biomedical Applications

   https://doi.org/10.3390/ma16062401  

   Medeiros, Mariana P.; Lopes, Debora R.; Kawasaki, Megumi; Langdon, Terence G.; Figueiredo, Roberto B. (March 2023, Materials)

   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. 

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2. The Microstructural Evolution and Corrosion Behavior of Zn-Mg Alloys and Hybrids Processed Using High-Pressure Torsion

   https://doi.org/10.3390/ma17010270  

   Tanji, Ayoub; Hermawan, Hendra; Boehlert, Carl J. (January 2024, Materials)

   Zinc (Zn) alloys, particularly those incorporating magnesium (Mg), have been explored as potential bioabsorbable metals. However, there is a continued need to enhance the corrosion characteristics of Zn-Mg alloys to fulfill the requirements for biodegradable implants. This work involves a corrosion behavior comparison between severe-plastic-deformation (SPD) processed cast Zn-Mg alloys and their hybrid counterparts, having equivalent nominal compositions. The SPD processing technique used was high-pressure torsion (HPT), and the corrosion behavior was studied as a function of the number of turns (1, 5, 15) for the Zn-3Mg (wt.%) alloy and hybrid and as a function of composition (Mg contents of 3, 10, 30 wt.%) for the hybrid after 15 turns. The results indicated that HPT led to multimodal grain size distributions of ultrafine Mg-rich grains containing MgZn2 and Mg2Zn11 nanoscale intermetallics in a matrix of coarser dislocation-free Zn-rich grains. A greater number of turns resulted in greater corrosion resistance because of the formation of the intermetallic phases. The HPT hybrid was more corrosion resistant than its alloy counterpart because it tended to form the intermetallics more readily than the alloy due to the inhomogeneous conditions of the materials before the HPT processing as well as the non-equilibrium conditions imposed during the HPT processing. The HPT hybrids with greater Mg contents were less corrosion resistant because the addition of Mg led to less noble behavior. 

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3. Multi-Scale Microstructural Characterization of Aluminum Alloys Subject to Advanced Processing Techniques for Improving Mechanical Properties

   Wu, Yun-Hsuan (August 2025, Oregon State University)

   This work presents a multi-scale microstructural characterization of aluminum alloys processed by high-pressure torsion (HPT) and cold angular rolling process (CARP) to improve their mechanical properties. Mechanical properties such as microhardness and tensile strength were correlated with microstructural features. To understand the processing-structure-property relationships, characterization methods spanning nano- to millimeter scales were used, including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and scanning transmission electron microscopy (STEM) EDS. TEM and STEM EDS were used to show that HPT of a Mg sheet sandwiched between Al sheets successfully produced a supersaturated solid solution (SSSS) of Mg in Al and several Al-Mg intermetallic phases, leading to significant grain refinement and increases in microhardness over pure Al. Although CARP has potential to induce the severe plastic deformation (SPD), the CARP system used in this work was not able to achieve SPD aluminum alloys. However, SEM EBSD characterization shows that CARP achieves an increase of the low-angle grain boundaries (LAGBs) and geometrically necessary dislocation (GND) density in Al-1043,which improves the mechanical properties. Moreover, a preliminary study was conducted on CAPR processed Al-6061 alloys to understand the synergistic effects precipitation and CARP-processing on the microstructure and properties. This research provides the critical insights into the capabilities and current limitations of CARP as a continuous SPD technique for aluminum alloys, and demonstrate the importance of integrated multi-scale characterization in understanding advanced materials processing. 

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4. Recent Developments in the Processing of Advanced Materials Using Severe Plastic Deformation

   https://doi.org/10.4028/www.scientific.net/MSF.1016.3  

   Kawasaki, Megumi; Figueiredo, Roberto B.; Langdon, Terence G. (January 2021, Materials Science Forum)

   null (Ed.)

   The processing of bulk metals through the application of severe plastic deformation (SPD), using procedures such as equal-channel angular pressing (ECAP) and high-pressure torsion (HPT), is now well established for the fabrication of materials with exceptionally small grain sizes, usually in the submicrometer range and often having grain sizes at the nanometer level. These grain sizes cannot be achieved using thermo-mechanical processing or any conventional processing techniques. Recently, these procedures have been further developed to process alternative advanced materials. For example, by stacking separate disks within the HPT facility for the synthesis of bulk nanocrystalline metastable alloys where it is possible to achieve exceptionally high hardness, or by pressing powders or metallic particles in order to obtain new and novel nanocomposites exhibiting unusual properties. 

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5. Advanced Characterization and Scalability of Severe Plastic Deformation Processes in Bulk Ultra-fined Grained Material

   Lee, Isshu (May 2025, Oregon State University)

   Severe plastic deformation (SPD) has been known for decades to provide microstructural refinement under a hydrostatic stress state by introducing a tremendous quantity of lattice defects, including vacancies, dislocations, and grain boundaries, leading to enhanced mechanical properties. Many SPD processes have been well studied and utilized for the processing of ultrafine-grained (UFG) metals and materials. One major challenge with SPD-processed UFG materials is their limited applicability, primarily due to their microstructural stability at elevated temperatures and the difficulty of scaling up to larger sizes or volumes. To first understand the thermal stability of UFG material, a copper prepared by high-pressure torsion, a technique that can achieve true nano-scale grains in bulk samples, was evaluated using two novel in situ techniques of micro-beam high-energy synchrotron X-ray diffraction. These are, namely, monochromatic X-ray beams that yield changes in microstructure with time and temperature, and a polychromatic X-ray beam that determines grain reorientation behavior during microstructural relaxation. Furthermore, a new processing technique named cold angular rolling process (CARP) demonstrated some promise as an SPD technique for producing theoretically unlimited lengths of strength-enhanced copper sheets at room temperature with a relatively low energy consumption. Additional miniature tensile testing incorporating digital image correlation (DIC) method and microstructural analysis utilizing high-energy X-ray diffraction determined the influence of CARP having higher shear strain hardening in comparison with other established techniques. This study highlights the significance of lattice-defect influenced mechanical properties and microstructure of UFG obtained across multi-length scales and volumes, which are critical for guiding the control and scalable production of advanced materials for commercialization. 

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