Materials Science Forum Vols. 667-669

Abstract: Nanostructured metals hold the potential to significantly augment the product portfolios of the metals industry. This potential is being progressively developed through contributions from the academic community to the underlying science of nanostructuring, increasing development and protection of intellectual property, and the involvement of large corporations. In this paper we review the trends and status of the commercialization of nanostructured metals technology, focusing on metals produced by severe plastic deformation.

Abstract: Future applications of ultrafine-grained, high performance materials produced by equal-channel angular pressing (ECAP) will most likely require processing on an industrial scale. There is a need for detailed microstructural and mechanical characterisation of large-scale, ECAP-processed billets. In the present study, we examine the microstructure and mechanical properties as a function of location and orientation within large (50 x 50 x 300 mm³) billets of an Al 6060 alloy produced by ECAP (90° channel angle) with different magnitudes of backpressure. The internal deformation is analysed using a grid-line method on split billets. Hardness is recorded in longitudinal and cross-sectional planes. In order to further characterise the local, post-ECAP mechanical properties, tensile tests in different layers are performed. Moreover, low voltage scanning transmission electron microscopy observations highlight relevant microstructural features. We find that the homogeneity and anisotropy of mechanical properties within the billets depend significantly on the geometry of the shear zone. We demonstrate that deformation gradients can be reduced considerably by increasing the backpressure: The opening-angle of the fan-shaped shear zone is reduced from ψ ≈ 20 ° to ψ ≈ 7 ° when the backpressure is increased from 0 to 150 MPa. Backpressures of 150 MPa result in excellent homogeneity, with a relative variation of tensile mechanical properties of less than 7 %. Our investigation demonstrates that ECAP is suitable for processing homogenous, high performance materials on a large scale, paving the way for advanced industrial applications.

Abstract: The paper reports on the investigation results for the criteria required for estimation of the SPD technologies. It has been demonstrated that one of the important criteria is specific surface area of the deformation zone, which enables considering the scale factor during processing and predicting the properties of the processed semi-products and items. Practical use of the results of conducted studies is demonstrated on the example of establishment of a production line for high-strength nanostructured semi-products from CP Ti for medical application.

Abstract: This work reports on the results of investigation of microstructure change of commercially pure titanium Grade 4 with the increase of the number of ECAP-Conform passes. There has been investigated influence of continuous equal-channel angular pressing by the scheme “Conform” (ECAP-C) on the structure and properties of commercially pure titanium Grade 4. It has been demonstrated that as a result of first two ECAP-C cycles titanium structure is strongly fragmented and deformation bands are formed. With the further increase of ECAP-C passes to 6 the band structure is transformed into ultrafine-grained (UFG) structure with the grain size of about 250 nm. The strength of titanium regularly grows with the increase of the number of ECAP-C passes, while ductility, which settles after first cycle on the level of 12%, is almost not changed with the further strain degree increase. As a result of the subsequent drawing of titanium after ECAP-C its strength additionally increases to 1300 MPa, with retention of ductility about 11%.

Abstract: The influence of ultrafine grains produced by severe plastic deformation technology on the weldability of Fe3Al and Al dissimilar materials was investigated. An ultrafine grain layer was produced on Fe3Al intermetallic compound by surface mechanical attrition treatment. Then the SMATed Fe3Al was diffusion bonded with 1060Al at 550°C for 90 min in the vacuum of 10-3 Pa. The microstructures of surface ultrafine grain layer and transition zone at the interface of SMATed-Fe3Al/Al joint were observed by scanning electron microscopy. The grain size of surface ultrafine grains was characterized by X-ray diffractometry. The elements distribution at the interface and the phase constituents of transition zone were measured by energy disperse spectroscopy. The results showed that a deformed layer about 10-20 μm wide and surface nanocrystallines about 35nm were produced after 15 min surface mechanical attrition. SMATed Fe3Al was well bonded with Al and 11-30 µm wide transition zone formed. The transition zone consisted of FeAl and FeAl3 phases. The surface nanocrystallines helped the atom diffusion and the formation of diffusion bonded joint with rough surface and lower pressure.

Abstract: The production of primary aluminum is an energy costly process. With the global warming being of concern, the secondary aluminum stream is becoming an even more important component of aluminum production and is attractive due to its economic and environmental benefits. Recycling of aluminum by new solid state recycling techniques instead of conventional remelting and subsequent refining processing can result in significant energy savings. Severe Plastic Deformation (SPD) techniques have been applied for consolidating nano particles into fully dense materials with good mechanical properties. However, solid state recycling of scraps by SPD is only in the beginning. In the present study, degreasing of aluminum chips from the machine workshop was investigated by a thermal method and chemical treatment. Thereafter, the decoated chips were recycled by Cyclic Extrusion Compression (CEC) at deformation temperatures between 400 and 500 °C. The microstructure and mechanical properties of the recycled aluminum scrap processed by SPD were subsequently investigated. The results show that SPD technology provides a promising alternative for recycling of aluminum scrap. Thermal degreasing of aluminum scrap resulted in more oxidization of aluminum scrap particles. Visible interfaces between chips were observed even at a low magnification.

Abstract: The mechanical and physical properties of ultrafine-grained titanium alloys produced by severe plastic deformation are considered. It is found that the formation of ultrafine-grained structure in these materials causes a significant enhancement in their mechanical properties at room temperature and in their resistance to hydrogen embrittlement as well as a change in their acoustic properties. Moreover, superplasticity is realized in these materials at less elevated temperatures relative to the respective coarse grained counterparts. It is shown that the above changes in material properties permit optimization of conditions by the production of items from the titanium alloys, e.g. medical implants having the requisite strength and stepped waveguides having long life even in the high power density conditions of an ultrasound system.

Abstract: An attempt has been made to fabricate highly cube textured ({001}<100>) polycrystalline nickel substrate tapes for coated superconductor applications using severe plastic deformation route. For this purpose high purity Ni (~99.97%) plates with widely different average grain size (28 µm or fine grained starting material and 650 µm or coarse grained starting material, respectively) are severely deformed by Accumulative Roll Bonding (ARB) up to an equivalent strain level of (εeq = 6.4) and annealed at various temperatures between 300° to 800°C for one hour. Upon annealing at different temperatures, the fine grained starting material developed a much stronger cube texture than the coarse grained starting material. By suitable annealing treatment near 100% cube textured tape could be obtained in the SPD processed fine grained nickel tapes having a predominantly low angle boundary network. The observed difference in the strength of cube texture in the two materials could be explained based on the oriented nucleation mechanism of formation of cube texture. The present results indicate that SPD processing route such as ARB is very effective in fabricating high purity Ni or Ni alloys intended for coated superconductor substrate applications.

Abstract: Commercial pure Ti (CP Ti) was subjected to the effects of ECAE processes at 673 K by Bc path. The initial 80~100 μm equiaxed and coarse grains were elongated along the shearing force direction of ECAE and refined to ~300 nm after the eight passes ECAE. Surface roughness of CP Ti samples and contact angle of deionized water on CP Ti surface, with coarse or ultrafine grains, modified by polish and HF treatment have been investigated. It is found that CP Ti substrates with ultrafine grains show a significantly lower water contact angle and higher surface energy compared with coarse-grains. HF treatment on pure Ti surfaces brings higher surface roughness and hydrophobicity than polish treated. These results reveal that the combination of ultrafine grains and higher surface roughness, hydrophobic allows a favorable condition for cell growth and bone generation on the surfaces of pure Ti after ECAE process.

Abstract: The work presents main achievements of international R&D activities of the Institute of Physics of Advanced Materials of Ufa State Aviation Technical University (IPAM USATU, Ufa, Russia) with a special attention to the innovative potential of nanostructured metals and alloys produced by severe plastic deformation (SPD) techniques. Examples of the first promising applications of bulk nanostructured materials (BNM) in medicine are considered and discussed.