High‐pressure sintering of ultrafine‐grained high‐entropy diboride

Herein the ultrafine-grained (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2)B 2 high-entropy diboride ceramics were successfully fabricated by high-pressure sintering technology for the first time. The results showed that the grain size, relative density, and Vickers hardness of the as-fabricated samples all increased gradually with increasing …

Strengthening mechanisms in an ultrafine-grained Al

The microstructures of an Al Zn Mg Cu alloy processed by high pressure torsion at room temperature and 200 °C were characterized by transmission Kikuchi diffraction and atom probe tomography.Hardening effects of different microstructural features including grain boundaries, dislocations and solute nanostructures were …

High-pressure strengthening in ultrafine-grained metals.

Understanding the strengthening of nanograined metals has been puzzling, as mixed results of both size softening and hardening have been reported 4-7.The main challenges in resolving this debate are the difficulty in synthesizing high-quality, ultrafine-grained metal samples for traditional tension or hardness tests and making statistically …

Nanoindentation analysis for local properties of ultrafine …

Severe plastic deformation (SPD) techniques have recently been developed for producing bulk ultrafine grained metallic materials. High pressure torsion (HPT) produces finer microstructures than those achieved by other SPD processes because of the higher imposed strain and hydrostatic pressure. It is known that HPT-processed metals …

Grain size dependent high-pressure elastic properties of ultrafine …

However, the differences diminish with increasing pressure, and the velocity crossover eventually takes place at approximately 20–30 GPa. The X-ray diffraction peaks of the ultrafine micro/nanocrystalline grossular samples significantly broaden between 15–40 GPa, especially for Gr179.

Processing of an ultrafine-grained titanium by high-pressure …

A commercial purity (CP) Grade 2 Ti was processed by high-pressure torsion (HPT) using an imposed pressure of 3.0 GPa at room temperature.The HPT processing reduced the grain size from ∼8.6 μm in the as-received state to ultra-fine grains (UFG) of ∼130 nm after HPT.Tensile testing showed the HPT-processed Ti exhibited a good …

Strengthening mechanisms in an ultrafine-grained …

The microstructures of an Al Zn Mg Cu alloy processed by high pressure torsion at room temperature and 200 °C were characterized by transmission Kikuchi diffraction and atom probe tomography. Hardening effects of different microstructural features including grain boundaries, dislocations and solute nanostructures were …

High‐pressure sintering of ultrafine‐grained …

Herein the ultrafine-grained (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2)B 2 high-entropy diboride ceramics were successfully fabricated by high-pressure sintering technology for the first time. The results showed …

High-pressure strengthening in ultrafine-grained metals

High-pressure strengthening in ultrafine-grained metals. Published Web Location. The Hall-Petch relationship, according to which the strength of a metal increases as the grain size decreases, has been reported to break down at a critical grain size of around 10 to 15 nanometres 1,2. As the grain size decreases beyond this point, the dominant ...

Different models of hardness evolution in ultrafine-grained materials

High-pressure torsion (HPT) is an attractive processing method in severe plastic deformation techniques involving the application of high compressive pressure with concurrent torsional straining. Excellent grain refinement is anticipated when using this technique to average grain sizes of the submicrometer or even nanometer ranges. …

Grain size dependent high-pressure elastic properties of ultrafine …

The ultrafine micro/nanocrystalline silicate samples synthesized by ultra-high-pressure methods are optically excellent for Brillouin scattering experiments, although the obtained sound velocity values need to be evaluated with caution especially for samples with smaller than 100 nm grain size.

Ultrafine-grained magnesium–lithium alloy processed by …

A Mg–Li alloy with 8 wt% Li was processed by severe plastic deformation (SPD) through the process of high-pressure torsion (HPT) to achieve ultrafine grains …

High-pressure strengthening in ultrafine-grained metals

Our high-pressure experiments reveal continuous strengthening in samples with grain sizes from 200 nanometres down to 3 nanometres, with the strengthening …

High-pressure strengthening in ultrafine-grained metals

High-pressure strengthening in ultrafine-grained metals. The Hall-Petch relationship, according to which the strength of a metal increases as the grain size decreases, has been reported to break down at a critical grain size of around 10 to 15 nanometres 1,2. As the grain size decreases beyond this point, the dominant mechanism of deformation ...

Ultrafine-Grained Materials | SpringerLink

Different superplastic deformation processes such as equal-channel angular pressing, high-pressure torsion, accumulative roll bonding, friction stir processing, …

High-pressure strengthening in ultrafine-grained metals

High-pressure strengthening in ultrafine-grained metals. Simulations and transmission electron microscopy reveal that the high strength observed in nickel of grain size 3 nanometres is caused by the superposition of strengthening mechanisms: both partial and full dislocation hardening plus suppression of grain boundary plasticity. Expand.

High-pressure strengthening in ultrafine-grained metals

Our high-pressure experiments reveal continuous strengthening in samples with grain sizes from 200 nanometres down to 3 nanometres, with the strengthening enhanced (rather than reduced) at grain sizes smaller than 20 nanometres. Here, we achieve a yield strength of approximately 4.2 gigapascals in our 3-nanometre-grain-size …

Sintering of ultrafine diamond particles under high …

Sintering of ultrafine diamond particles Ni-Zr (10 wt.% Zr) alloy was used as the sintering aid instead of nickel metal. The diamond powder of size 0.5 1.5 p.rn was sintered under a high pressure of 5.8 GPa at 1350 for 5-30min with the Ni-Zr alloy. It was found in the experiment that the abnormal grain growth of diamond did not occur.

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Microstructural, mechanical and tribological properties of ultrafine …

The effect of temperature on tribological properties of coarse grained (CG) and ultrafine-grained (UFG) Cu–Cr–Zr alloy processed via high pressure torsion (HPT) was investigated. Dominant wear mechanism depends on both temperature and microstructure of the alloy.

High-pressure strengthening in ultrafine-grained …

Our high-pressure experiments reveal continuous strengthening in samples with grain sizes from 200 nanometres down to 3 nanometres, with the strengthening enhanced (rather than reduced) at...

Hard and tough ultrafine-grained B4C-cBN composites prepared by high

Tough and hard ultrafine-grained B 4 C-cBN composites were firstly fabricated by high-pressure sintering mixed B 4 C and cBN nanopowders at 6 GPa and 1700 °C. The phase transition from cBN to hBN is avoided by high pressure during the sintering process.The effects of the cBN content on the densification and mechanical …

High‐pressure sintering of ultrafine‐grained high‐entropy …

Dense and pure high-entropy metal diboride ceramics sintered from self-synthesized powders via boro/carbothermal reduction approach. Equimolar quinary diboride powders, with nominal composition of (Ti0.2Hf0.2Zr0.2Nb0.2Ta0.2)B2, were synthesized by boro/carbothermal reduction (BCTR) of oxide mixtures (MOx, M = Ti, Hf, Zr, Nb and….

Preparation of ultrafine-grained GH4169 superalloy by high-pressure

The distorted microstructure after HPT was replaced with the newly formed fine grain without distortion, eventually forming an ultrafine grain structure with high-angle grain boundaries. After HPT processing was performed at 5 GPa × 2 turns, a cubic texture in the {100}<001> direction was produced in the GH4169 superalloy.

Full article: Ultra-strong and strain-hardenable ultrafine …

An equiatomic VCoNi medium-entropy alloy possesses high sensitivity to grain-boundary strengthening, achieved by severe lattice distortions. Its ultrafine-grain …

High-pressure strengthening in ultrafine-grained …

High-pressure strengthening in ultrafine-grained metals Xiaoling Zhou 1,2,3,14, Zongqiang Feng 4,14, Linli Zhu 5,6,14, Jianing Xu 1,7,14, ... Our high-pressure experiments reveal continuous strengthening in samples with grain sizes from 200 nanometres down to 3 nanometres, with the strengthening enhanced (rather than reduced) at grain sizes ...

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Microstructure and mechanical properties of ultrafine-grained …

In addition to processing of ultrafine-grained (UFG) and nanocrystalline microstructures in bulk coarse-grained materials, ... Jahedi et al. [20] showed that unconstrained HPT and high pressure double torsion processes with hollow holder can be successfully used for consolidation of metallic powders. If the initial powder is coarse …

(PDF) High pressure sintering of ultrafine grained high‐entropy

Herein the ultrafine grained (Hf0.2Zr0.2Ta0.2Nb0.2Ti0.2)B2 high‐entropy diboride ceramics was successfully fabricated by high pressure sintering technology for the first time. The results showed ...

Outstanding mechanical properties of ultrafine-grained …

Introduction. Severe plastic deformation (SPD) is an efficient strategy for creating a high density of line defects (dislocation) in metals. The combination of large shear strain with high hydrostatic pressure, which is caused by SPD, reduces the grain size of the alloy, vacancy agglomerates, and nanoprecipitation [[1], [2], [3], [4]].

High-pressure strengthening in ultrafine-grained metals

We achieve a yield strength of approximately 4.2 gigapascals in our 3-nanometre-grain-size samples, ten times stronger than that of a commercial nickel material. A maximum flow …

High-pressure strengthening in ultrafine-grained …

We achieve a yield strength of approximately 4.2 gigapascals in our 3-nanometre-grain-size samples, ten times stronger than that of a commercial nickel material. A maximum flow stress of 10.2 ...