Влияние температуры деформации на эффект реализации высокой пластичности в ультрамелкозернистом сплаве Al-1.5Cu

For the first time the influence of temperature of mechanical tension on the plastification effect (PE) in ultrafine-grained (UFG) Al-1.5Cu (wt.%) alloy was studied. The UFG structure in the material was formed by high pressure torsion (HPT). A significant increase in the plasticity (from ~ 3% to 22%) of the UFG alloy while maintaining high ultimate tensile strength (450 MPa) was achieved by additional treatment, including low temperature annealing and subsequent small additional HPT deformation. The temperature range of the PE implementation was revealed. It was shown that decrease of the deformation temperature leads to a gradual decrease of the PE and its disappearance at –20 oC. Cu alloying led to a significant narrowing of the range of PE implementation from low temperature side compared to the UFG commercially pure Al. Possible reasons of the influence of Cu alloying on temperature dependence of the PE are discussed.

Ionic liquid–based click-ionogels

Gels that are freeze-resistant and heat-resistant and have high ultimate tensile strength are desirable in practical applications owing to their potential in designing flexible energy storage devices, actuators, and sensors. Here, a simple method for fabricating ionic liquid (IL)–based click-ionogels using thiol-ene click chemistry under mild condition is reported. These click-ionogels continue to exhibit excellent mechanical properties and resilience after 10,000 fatigue cycles. Moreover, due to several unique properties of ILs, these click-ionogels exhibit high ionic conductivity, transparency, and nonflammability performance over a wide temperature range (−75° to 340°C). Click-ionogel–based triboelectric nanogenerators exhibit excellent mechanical, freeze-thaw, and heat stability. These promising features of click-ionogels will promote innovative applications in flexible and safe device design.

Evolution of Secondary α Phase during Aging Treatment in Novel near β Ti-6Mo-5V-3Al-2Fe Alloy

Evolution of secondary α phase during aging treatment of a novel near β titanium alloy Ti-6Mo-5V-3Al-2Fe(wt.%) was studied by OM, SEM, and TEM. Results indicated that size and distribution of secondary α phase were strongly affected by aging temperature and time. Athermal ω phase formed after super-transus solution treatment followed by water quenching, and promoted nucleation of needle-like intragranular α in subsequent aging process. When aged at 480 °C, fine scaled intragranular α with small inter-particle spacing precipitated within β grains and high ultimate tensile strength above 1500 MPa was achieved. When the aging temperature increased, the size and inter-particle spacing of intragranular α increased and made the strength reduce, but the ductility got improved. When aging temperature reached as high as 600 °C, ω phase disappeared and intragranular α coarsened obviously, resulting in serious decrease of strength. While mutually parallel Widmanstätten α laths formed at the vicinity of β grain boundaries and grew into the internal area of β grains, and significant improvement of ductility was achieved. As the aging time increased from 4 h to 16 h at 600 °C, the intragranular α grew slightly and brought about minor change of mechanical properties.

Tensile Properties of Ti-6Al-4V Discs Produced by Open Die Powder Compact Forging of Pre-Alloyed HDH Powders

Open die powder compact forging was employed for consolidation of Ti-6Al-4V(wt.%) powders which were produced by a hydride-dehydride (HDH) process. The powders were initially warm-compacted into cylindrical shapes. Induction heating was used for preheating the compacts prior to forging into plates. The effect of the forging parameters such as temperature and pre-sintering time on the microstructure and tensile properties of the forged plates were studied. Porosity and the alpha-beta phase distribution were investigated to enable a better understanding of their effect on the fracture behaviour of the tensile tested specimens. The fracture surfaces of the broken tensile specimens were analysed using Scanning Electron Microscopy (SEM) to find the correlation between microstructure, residual porosity and fracture behaviour. A combination of high ultimate tensile strength of over 1200MPa and a good ductility reflected by an elongation to fracture of around 10% was achieved in some of the forged discs.

Mechanical Behavior and Stress-Induced Martensitic Transformation in Nanocrystalline Ti49.4Ni50.6 Alloy

Amorphous-nanocrystalline Ti49.4Ni50.6 alloy in the shape of a disc 20 mm in diameter has been successfully produced using high pressure torsion (HPT). Application of HPT and annealing at temperatures of 300–550°C resulted in formation of a nanocrystalline (NC) structure with the grain size (D) about 20–300 nm. The HPT samples after annealing at Т = 400°C with the D= 20 nm possess high yield stress and high ultimate tensile strength (more than 2000 MPa). There is an area of strain-induced transformation B2-B19’ on the tensile curve of the samples with the grain size D =20 nm. The stress of martensitic transformation (σm) of samples is 450 MPa, which is three times higher than σm in the initial coarse-grained state (σm ≈ 160 MPa). The HPT samples after annealing at Т = 550°C with the D= 300 nm possess high ductility (δ>60 %) and high ultimate tensile strength (about 1000 MPa).

Materials and Processing Designs for High-Performance Magnesium Alloys

Materials and processing designs for advanced magnesium alloys with fine microstructures and superior properties were established by the combination of the repeated plastic working and the Mg2Si synthesis in solid-state. The grain size was less than 1 μm via RPW process due to its severe plastic working on raw powder. The hot extruded magnesium alloys produced in industries showed high ultimate tensile strength, e.g. 420~450MPa, when employing Mg-Zn-Al-Ca-RE (Rare Earth) alloy coarse powder, having 0.5~2 mm diameter, as input materials.