On the origin of extremely high strength of ultrafine-grained Al alloys produced by severe plastic deformation

Ultrafine-grained Al alloys produced by high pressure torsion are found to exhibit a very high strength, considerably exceeding the Hall-Petch predictions for the ultrafine grains. The phenomena can be attributed to the unique combination of ultrafine structure and deformation-induced segregations of solute elements along grain boundaries, which may affect the emission and mobility of intragranular dislocations

Ultrafine grained titanium for biomedical applications: An overview of performance

AbstractUltrafine grain sized titanium (UFG Ti) obtained by severe plastic deformation presents a bright potential for biomedical applications because it provides the strength of titanium alloys without toxic alloying elements, such as Al and V that, by dissolving away from the implant, may be harmful to human health. The most recent developments and challenges in this field are reviewed. UFG Ti mini-devices were implanted in rabbits and the removal torque was compared with that of conventional commercially pure (cp) grain sized Ti Grade 2 and Ti6Al4V alloy Grade 5. The osseointegration of the UFG Ti was slightly superior of that of cp Ti Grade 2. The microstructure and mechanical properties of the UFG Ti, with special emphasis on dental implant application are reviewed and some additional properties evaluated and presented

Polyfunctional Modifiers for Bitumen and Bituminous Materials with High Performance

Over the last decade increase in capacity and the intensity of vehicular traffic has increased manifoldly, including heavy trucks, super singles, and higher tire pressures, resulting in significant increase of dynamic loads on the road surface which in turn lead to high quality requirements for bitumen in order to avoid premature wear and failure of asphalt concrete pavements. One of the possibilities to increase the quality of bitumen is to use special additives and modifiers that can provide a high adhesion to mineral filler and inhibit the aging and degradation processes in the asphalt coating. To achieve this, in the present study composite modifiers based on bisimidazolines derivatives were synthesized. The developed polyfunctional modifier (PFM) of complex action provides enhanced thermal stability, significantly improves the adhesion between bitumen binder and aggregates, and also improves the physical-mechanical properties of the asphalt concrete. Based on the test results it is recommended to use the synthesized samples of the PFM additive with complex action in asphalt mixtures for road paving

Effect of Grain Size on the Irradiation Response of Grade 91 Steel Subjected to Fe Ion Irradiation at 300 °C

Irradiation using Fe ion at 300 °C up to 100 dpa was carried out on three variants of Grade 91 (G91) steel samples with different grain size ranges: fine-grained (FG, with blocky grains of a few micrometers long and a few hundred nanometers wide), ultrafine-grained (UFG, grain size of ~ 400 nm) and nanocrystalline (NC, lath grains of ~ 200 nm long and ~ 80 nm wide). Electron microscopy investigations indicate that NC G91 exhibit higher resistance to irradiation-induced defect formation than FG and UFG G91. In addition, nano-indentation studies reveal that irradiation-induced hardening is significantly lower in NC G91 than that in FG and UFG G91. Effective mitigation of irradiation damage was achieved in NC G91 steel in the current irradiation condition. Graphical abstract: [Figure not available: see full text.

Comparison of the Thermal Stability in Equal-Channel-Angular-Pressed and High-Pressure-Torsion-Processed Fe–21Cr–5Al Alloy

Nanostructured Steels Are Expected to Have Enhanced Irradiation Tolerance and Improved Strength. However, They Suffer from Poor Microstructural Stability at Elevated Temperatures. in This Study, Fe–21Cr–5Al–0.026C (Wt%) Kanthal D (KD) Alloy Belonging to a Class of (FeCrAl) Alloys Considered for Accident-Tolerant Fuel Cladding in Light-Water Reactors is Nanostructured using Two Severe Plastic Deformation Techniques of Equal-Channel Angular Pressing (ECAP) and High-Pressure Torsion (HPT), and their Thermal Stability between 500–700 °C is Studied and Compared. ECAP KD is Found to Be Thermally Stable Up to 500 °C, Whereas HPT KD is Unstable at 500 °C. Microstructural Characterization Reveals that ECAP KD Undergoes Recovery at 550 °C and Recrystallization above 600 °C, While HPT KD Shows Continuous Grain Growth after Annealing above 500 °C. Enhanced Thermal Stability of ECAP KD is from Significant Fraction (\u3e50%) of Low-Angle Grain Boundaries (GBs) (Misorientation Angle 2–15°) Stabilizing the Microstructure Due to their Low Mobility. Small Grain Sizes, a High Fraction (\u3e80%) of High-Angle GBs (Misorientation Angle \u3e15°) and Accordingly a Large Amount of Stored GB Energy, serve as the Driving Force for HPT KD to Undergo Grain Growth Instead of Recrystallization Driven by Excess Stored Strain Energy

Effect of Zn content on microstructure evolution in Al–Zn alloys processed by high-pressure torsion

Al–Zn alloys having different Zn contents of 2, 5, 10 and 30 wt% were processed by high-pressure torsion (HPT) to produce ultrafine-grained (UFG) materials. Microstructural features of these UFG Al–Zn alloys were investigated using depth-sensing indentations, focused ion beam (FIB), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). Emphasis was placed on the microstructure evolution of the alloys with different Zn-concentration which demonstrated substantially different mechanical behavior, exhibiting superductility with increasing Zn content. It was shown that in every case, HPT resulted decomposition in the microstructure, but there is a significant difference between the microstructures of alloys with low and high Zn content. Based on the microstructural observations, a scenario is proposed about that how the decomposed microstructure developed during HPT process in low- and high Zn-containing Al–Zn alloys, influencing their mechanical behavior

Estimation of Potential Capability of Natural Bitumens and High Viscosity Oils for Refining According to Fuel-Bitumen Scheme

According to different estimates, geological heavy oil and natural bitumens resources at the Tatarstan deposits make 1,5- 7 billion tons. On the territory of Tatarstan across all bituminous horizons about 450 deposits of natural bitumens have been found. One third of deposits of this raw materials existing in Russia fall on the share of Tatarstan. Natural bitumens are valuable material for production of fine chemicals that are used in different spheres of life activities