https://material.karlov.mff.cuni.cz/people/janecek/studenti/FyzMetNano/Estrin_AM61_2013_782.pdf

Extreme grain refinement by severe plastic deformation: A wealth of challenging science

With the presentation of a theory of liquid alloys, we have now assembled all the necessary tools for the ab initio construction of an alloy phase diagram.

Alloy Phase Diagrams

The excellent cryogenic tensile properties of the CrMnFeCoNi alloy are generally caused by deformation twinning, which is difficult to achieve at room temperature because of insufficient stress for twinning. Here, we induced twinning at room temperature to improve the cryogenic tensile properties of the CrMnFeCoNi alloy. Considering grain size effects on the critical stress for twinning, twins were readily formed in the coarse microstructure by cold rolling without grain refinement by hot rolling. These twins were retained by partial recrystallization and played an important role in improving strength, allowing yield strengths approaching 1 GPa. The persistent elongation up to 46% as well as the tensile strength of 1.3 GPa are attributed to additional twinning in both recrystallized and non-recrystallization regions. Our results demonstrate that non-recrystallized grains, which are generally avoided in conventional alloys because of their deleterious effect on ductility, can be useful in achieving high-strength high-entropy alloys.

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Cryogenic strength improvement by utilizing room-temperature deformation twinning in a partially recrystallized VCrMnFeCoNi high-entropy alloy

In the circular economy, products, components, and materials are aimed to be kept at the utility and value all the lifetime. For this purpose, repair and remanufacturing are highly considered as proper techniques to return the value of the product during its life. Directed Energy Deposition (DED) is a very flexible type of additive manufacturing (AM), and among the AM techniques, it is most suitable for repairing and remanufacturing automotive and aerospace components. Its application allows damaged component to be repaired, and material lost in service to be replaced to restore the part to its original shape. In the past, tungsten inert gas welding was used as the main repair method. However, its heat affected zone is larger, and the quality is inferior. In comparison with the conventional welding processes, repair via DED has more advantages, including lower heat input, warpage and distortion, higher cooling rate, lower dilution rate, excellent metallurgical bonding between the deposited layers, high precision, and suitability for full automation. Hence, the proposed repairing method based on DED appears to be a capable method of repairing. Therefore, the focus of this study was to present an overview of the DED process and its role in the repairing of metallic components. The outcomes of this study confirm the significant capability of DED process as a repair and remanufacturing technology.

Application of Directed Energy Deposition-Based Additive Manufacturing in Repair

http://ercnsm.osu.edu/sites/ercnsm.osu.edu/files/uploads/S_press/650.pdf

Mechanical servo press technology for metal forming

Influence of cryo-rolling reduction and annealing of commercially pure (CP) Al is evaluated in four aspects: microstructure, mechanical properties, electrical conductivity and general corrosion. It is shown that by selecting optimal cryo-rolling reduction and subsequent annealing condition result in ultrafine grains in CP Al with good combination of high strength and ductility. Electrical conductivity of the cryo-rolled samples decreased due to increased number of the electron scattering centers (lattice defects and grain boundary area). However, optimization of cryo-rolling and annealing treatment could restore the conductivity coupled with high strength in CP Al. Corrosion behaviour of cryo-rolled CP Al improved after annealing treatment. High dissolution rate and low thermal stability of the ultrafine grain structure could override the anticipated advantage of uniform corrosion in ultrafine grain CP Al.

Effect of cryo-rolling and annealing on microstructure and properties of commercially pure aluminium

Production of ultrafine grain sizes in aluminium sheets by severe plastic deformation using the technique of groove pressing

Commercial purity copper sheets were subjected to a severe plastic deformation technique called groove pressing (GP) to a strain of 3.48 at both room and cryogenic temperatures. The mechanical properties and microstructure were studied as a function of the number of passes. A deformed microstructure with cell sizes approximately 0.5 μm in size were obtained from a starting annealed grain size of 78 μm.

Applicability of the groove pressing technique for grain refinement in commercial purity copper

Candidature of equal channel angular pressing for processing of tubular commercial purity-titanium

The present investigation attempts to understand the friction welding characteristics of sintered P/M steel preforms–wrought copper dissimilar parts. In order to achieve sound weld between these two materials the process parameters were optimized and inferred that the preforms of lower densities with lower process parameters yields quality weldments, established through post-weld tests. This study also envisages the influence of process parameters which include resident preform densities, friction pressure, upset pressure, and burn-off length on microstructure and mechanical properties of the welds. This work consolidates information on the aspects of joining P/M component with wrought materials for practical execution.

P. Venugopal

Papers

Effect of cryo-rolling and annealing on microstructure and properties of commercially pure aluminium

Production of ultrafine grain sizes in aluminium sheets by severe plastic deformation using the technique of groove pressing

Applicability of the groove pressing technique for grain refinement in commercial purity copper

Candidature of equal channel angular pressing for processing of tubular commercial purity-titanium

Investigations on the continuous drive friction welding of sintered powder metallurgical (P/M) steel and wrought copper parts