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Introduction to Metallic Glasses
Published in Sumit Sharma, Metallic Glass–Based Nanocomposites, 2019
This method solves the problem of sample size where it is difficult to produce samples of larger diameters as well as the challenges involved in fast cooling of the samples. Amorphous powders are produced by different techniques, e.g., mechanical alloying, high-pressure gas atomization, or atomization. The powders are then densified using different procedures, e.g., cold pressing, equal channel angular extrusion, hot pressing, and, the most efficient method, spark plasma sintering (SPS). This method can be improved by the introduction of heat energy during sintering and then rapid cooling. This method has proven to be time-saving and cost-effective, though challenges of incorporation of impurities may pose problems [24].
The structure and mechanical properties of nanocrystals
Published in A. M. Glezer, E. V. Kozlov, N. A. Koneva, N. A. Popova, I. A. Kurzina, Plastic Deformation of Nanostructured Materials, 2017
A. M. Glezer, E. V. Kozlov, N. A. Koneva, N. A. Popova, I. A. Kurzina
Increasing the strength properties by grain refining is an effective technique which can be used for all types of metallic materials [21]. In the last decade, different grain refining processes were developed by metal physicists. The most effective of these are various variants of severe plastic deformation (SPD): 1) equal channel angular pressing (ECAP) [16,17,21â23] $ [16,17,21-23] $ and its various modifications, for example, equal channel angular extrusion (ECAE) [24], matched ECAP (ECAP-M)[25] when the metal is pushed through a channel having the shape of a circle, a combination of extrusion and ECAP [26], dissimilar angular pressing [16,27], equal channel angular drawing [21,28]; 2) high pressure torsion (HPT) [29,30]; 3) various methods of deep rolling deformation [29]; 4) combined methods (torsion plus rolling) [31,32], shear under high pressure [33], and others. In principle, it was possible to reduce the grain sizes by least 2-4 orders of magnitude compared to the previously used fine grains [34].
Mg with High Purity for Biomedical Applications
Published in Yufeng Zheng, Magnesium Alloys as Degradable Biomaterials, 2015
According to the results of Fan et al. (2012), as-cast CP-Mg (99.88 wt.%) was hot quadratic extruded into a rectangular bar at a reduction ratio of 12:1, then followed by ECAP. Mechanical test results showed that the elongation to failure of the ECAPed pure Mg was enhanced to 27% without sacrificing the strength after extrusion. In addition, fine grains smaller than 5 μm were obtained. Yamashita et al. (2001) examined the microstructure and mechanical property of pure Mg (99.9%) subjected to ECAP processing at 400°C. Reduced grain sizes of Mg were observed under all pressing conditions attributed to the occurrence of recrystallization during pressing. Meanwhile, the tensile testing indicated a significant improvement in both strength (improvement > 160%) and ductility. Equal channel angular extrusion (ECAE) is one of the most effective ways for the grain refinement of pure Mg. Biswas et al. (2010) demonstrated a way to impart severe plastic deformation to hot-rolled CP-Mg (99.93%) at room temperature to produce an ultrafine grain size of ~250 nm with significantly improved strength through ECAE as shown in Figure 5.8.
Deformation-induced changes in single-phase Al-0.1Mg alloy
Published in Philosophical Magazine, 2018
The results of extensive theoretical and experimental work on developing fine and ultra-fine microstructures using equal channel angular extrusion (ECAE) and other methods of severe plastic deformation to high strains [17–21] have expanded the possibilities for research on DGG. ECAE is one of the methods used to deform metallic specimens to high and ultra-high strains without any net change in their dimensions. During ECAE, the sample is extruded in a closed die that has two intersecting channels of the equal cross-section with an internal angle 2θ between them. The lubricated billet is forced from one channel to the other by applying a pressure and a shear is introduced to the material when it crosses the plane of intersection between the two channels. Experimental and modelling results related to processing using ECAE [22] have shown that most parts of the billet are deformed homogeneously. Zones, which are not deformed or deformed to a lesser extent, are generally located at the ends of the sample.