Temperature and strain rate dependence of microstructural evolution and dynamic mechanical behavior in nanocrystalline Ti

The mechanical behavior of commercial purity titanium with a nanocrystalline (NC) grain size was investigated using split Hopkinson pressure bar tests at high strain rates and over a range of temperatures. The study was accompanied by detailed microstructural investigations before and after compression testing. The results show that rotary dynamic recrystallization operates during compressive deformation at strain rates of ~3000 and ~4500 s?1 at temperatures from 298 to 573 K but cells form at 673 K. The dynamic mechanical behavior of NC Ti shows a strong dependence on temperature and strain rate such that the flow stress and the strain hardening rate both increase with increasing strain and decreasing temperature. A constitutive equation is derived to relate the flow stress to the temperature, strain rate and true strain and to predict the yield strength and the peak stress of NC Ti subjected to dynamic deformation at elevated temperatures

Effect of grain size on compressive behaviour of titanium at different strain rates

An investigation was conducted to evaluate the dependence on grain size of the compressive deformation of commercial purity (CP) Ti. Tests were performed at room temperature using grain sizes from coarse-grained CG (20 ?m) to ultrafine-grained UFG (500 nm) and nanocrystalline NC (90 nm) with testing strain rates in the range from 0.01 to 10 s?1. The results show the flow stress and the strain rate sensitivity of CP Ti increase with decreasing grain size. Work hardening dominates at all strain rates in CG Ti but it balances with flow softening at 0.01 and 0.1 s?1 in UFG and NC Ti and there is obvious flow softening in these two materials at 10 s?1

Regularities of Microstructure Evolution in a Cu-Cr-Zr Alloy during Severe Plastic Deformation

The effect of severe plastic deformation by the conforming process of equal channel angular extrusion (ECAE-Conform) followed by cold rolling on the microstructures developed in a Cu-0.1Cr-0.1Zr alloy was investigated. Following the ECAE-Conform of 1 to 8 passes (corresponding strains were 0.8 to 6.4) cold rolling to a total strain of 4 was accompanied by substantial grain refinement and strengthening. An average grain size tended to approach 160 nm with an increase in the rolling reduction. An increase in the ECAE-Conform strain promoted the grain refinement during subsequent cold rolling. The fraction of the ultrafine grains with a size of 160 nm after cold rolling to a strain of 4 increased from 0.12 to 0.52 as the number of ECAE-Conform passes increased from 1 to 8. Correspondingly, the yield strength increased above 550 MPa. The strengthening could be expressed by a Hall–Petch type relationship with a grain size strengthening factor of 0.11 MPa m0.5

Influence of the Chromium Content in Low-Alloyed Cu–Cr Alloys on the Structural Changes, Phase Transformations and Properties in Equal-Channel Angular Pressing

The quantitative concentration of alloying elements in low-alloyed copper alloys is an important factor in forming electrical and mechanical characteristics. It is known that severe plastic deformation is accompanied by both a substantial refinement of the structure and changes in the kinetics of phase transformations during the deformation and the post-deformation thermal treatment. This paper presents the results of a comparative analysis of the Cu–0.2Cr and Cu–1.1Cr alloys subjected to equal-channel angular pressing at room temperature. The analysis was performed for the grain structure, solid solution, and second-phase particles using transmission electron microscopy, scanning electron microscopy, X-ray crystal analysis, and the small-angle diffraction method. It was found that the level of structure refinement and mechanical characteristics after equal-channel angular pressing was almost the same for both studied alloys. Post-deformation aging of the Cu–0.2Cr alloy leads to the development of polygonization and re-crystallization within it. The aging of the Cu–1.1Cr alloy shows a better thermal stability than that of the Cu–0.2Cr alloy. In the Cu–1.1Cr alloy, after aging, in comparison with Cu–0.2Cr, a denser-packed ensemble of fine particles with an average size of 54 ± 2 nm is formed. In this case, the average size of fragments is 270 ± 15 nm and the ultimate tensile strength reaches 485 MPa

Development and Research of Method CCRE-SPD for Obtaining Aluminum Semi-Finished Products of High Quality

В статье представлены исследования метода СЛИПП-ИПД с использованием математического моделирования в программном комплексе DEFORM-3D. Показано, что данный метод имеет потенциальные возможности для улучшения качества продукции за счет формирования более однородных структурных состояний, в том числе и в ультрамелкозернистом диапазоне за счет высокого уровня накопленной сдвиговой деформации в процессе обработкиThis work represents studies of CCRE-SPD method with using mathematic modeling in program complex DEFORM-3D. It is shown that this method has the potential to improve product quality through the formation of a more homogeneous structure states, including in the ultrafinegrained range due to the high level of accumulated shear deformation during processin

Development and Research of Method CCRE-SPD for Obtaining Aluminum Semi-Finished Products of High Quality

В статье представлены исследования метода СЛИПП-ИПД с использованием математического моделирования в программном комплексе DEFORM-3D. Показано, что данный метод имеет потенциальные возможности для улучшения качества продукции за счет формирования более однородных структурных состояний, в том числе и в ультрамелкозернистом диапазоне за счет высокого уровня накопленной сдвиговой деформации в процессе обработкиThis work represents studies of CCRE-SPD method with using mathematic modeling in program complex DEFORM-3D. It is shown that this method has the potential to improve product quality through the formation of a more homogeneous structure states, including in the ultrafinegrained range due to the high level of accumulated shear deformation during processin

Superior Strength of Austenitic Steel Produced by Combined Processing, including Equal-Channel Angular Pressing and Rolling

Enhancement in the strength of austenitic steels with a small content of carbon can be achieved by a limited number of methods, among which is ultrafine-grained (UFG) structure formation. This method is especially efficient with the use of severe plastic deformation (SPD) processing, which significantly increases the contribution of grain-boundary strengthening, and also involves a combination of the other strengthening factors (work hardening, twins, etc.). In this paper, we demonstrate that the use of SPD processing combined with conventional methods of deformation treatment of metals, such as rolling, may lead to additional strengthening of UFG steel. In the presented paper we analyze the microstructure and mechanical properties of the Cr–Ni stainless austenitic steel after a combined deformation. We report on substantial increases in the strength properties of this steel, resulting from a consecutive application of SPD processing via equal-channel angular pressing and rolling at a temperature of 400 °C. This combined loading yields a strength more than 1.5 times higher than those produced by either of these two techniques used separately

Developing Nanostructured Ti Alloys for Innovative Implantable Medical Devices

Recent years have witnessed much progress in medical device manufacturing and the needs of the medical industry urges modern nanomaterials science to develop novel approaches for improving the properties of existing biomaterials. One of the ways to enhance the material properties is their nanostructuring by using severe plastic deformation (SPD) techniques. For medical devices, such properties include increased strength and fatigue life, and this determines nanostructured Ti and Ti alloys to be an excellent choice for the engineering of implants with improved design for orthopedics and dentistry. Various reported studies conducted in this field enable the fabrication of medical devices with enhanced functionality. This paper reviews recent development in the field of nanostructured Ti-based materials and provides examples of the use of ultra-fine grained Ti alloys in medicine