Effect of Chemical Composition on Grain Refinement of AlxCoCrFeNi High Entropy Alloys with NiAl Grain Boundary Precipitates

2021 ◽  
Vol 1016 ◽  
pp. 1690-1695
Author(s):  
Hiroyuki Y. Yasuda ◽  
Hiroyuki Miyamoto ◽  
Takuya Inagaki ◽  
Ken Cho ◽  
Takeshi Nagase
Keyword(s):  
Grain Refinement ◽  
Volume Fraction ◽  
High Entropy Alloys ◽  
High Entropy ◽  
Nial Phase ◽  
Ultrafine Grained ◽  
Average Grain Size ◽  
Ultrafine Grained Microstructure ◽  
B2 Structure ◽  
Smith Model

In AlxCoCrFeNi high entropy alloys (x = 0.3–0.5), the NiAl phase with the B2 structure is precipitated rapidly along the fcc grain boundaries. During recrystallization after conventional cold rolling, the NiAl precipitates effectively suppress the grain growth, which results in the ultrafine-grained microstructure. It should be noted that no severe plastic deformation is necessary to obtain the microstructure. The volume fraction of the NiAl precipitates increases with increasing x. As a result, the average grain size of the fcc matrix (dm) after the recrystallization decreases with increasing x, and therefore, a minimum dm of 0.5 μm can be obtained at x = 0.5. The grain refinement by the NiAl precipitates is consistent with the Zener-Smith model. At x = 0.5, the alloy with dm = 0.5 μm exhibits a yield stress of 1163 MPa and an elongation of 24% at room temperature.

scholarly journals Enhanced strength–ductility synergy in ultrafine-grained eutectic high-entropy alloys by inheriting microstructural lamellae

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Peijian Shi ◽  
Weili Ren ◽  
Tianxiang Zheng ◽  
Zhongming Ren ◽  
Xueling Hou ◽  
...  
Keyword(s):  
High Entropy Alloys ◽  
High Entropy ◽  
Ultrafine Grained

Deformation behavior of nanocrystalline and ultrafine-grained CoCrCuFeNi high-entropy alloys

2019 ◽  
Vol 34 (5) ◽  
pp. 720-731 ◽  
Author(s):  
Seungjin Nam ◽  
Jun Yeon Hwang ◽  
Jonggyu Jeon ◽  
Jihye Park ◽  
Donghyun Bae ◽  
...  
Keyword(s):  
Deformation Behavior ◽  
High Entropy Alloys ◽  
High Entropy ◽  
Ultrafine Grained ◽  
Image Position

Abstract

scholarly journals Prediction of Strength and Ductility in Partially Recrystallized CoCrFeNiTi0.2 High-Entropy Alloy

Entropy ◽  
2019 ◽  
Vol 21 (4) ◽  
pp. 389 ◽  
Author(s):  
Hanwen Zhang ◽  
Peizhi Liu ◽  
Jinxiong Hou ◽  
Junwei Qiao ◽  
Yucheng Wu
Keyword(s):  
Tensile Strength ◽  
Single Phase ◽  
Volume Fraction ◽  
Tensile Elongation ◽  
High Entropy Alloy ◽  
High Entropy Alloys ◽  
Number Density ◽  
High Entropy ◽  
Average Size ◽  
Strength And Ductility

The mechanical behavior of a partially recrystallized fcc-CoCrFeNiTi0.2 high entropy alloys (HEA) is investigated. Temporal evolutions of the morphology, size, and volume fraction of the nanoscaled L12-(Ni,Co)3Ti precipitates at 800 °C with various aging time were quantitatively evaluated. The ultimate tensile strength can be greatly improved to ~1200 MPa, accompanied with a tensile elongation of ~20% after precipitation. The temporal exponents for the average size and number density of precipitates reasonably conform the predictions by the PV model. A composite model was proposed to describe the plastic strain of the current HEA. As a consequence, the tensile strength and tensile elongation are well predicted, which is in accord with the experimental results. The present experiment provides a theoretical reference for the strengthening of partially recrystallized single-phase HEAs in the future.

scholarly journals Designing (Ultra)Fine-Grained High-Entropy Alloys by Spark Plasma Sintering and Equal-Channel Angular Pressing

Crystals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1157
Author(s):  
Lisa-Marie Rymer ◽  
Thomas Lindner ◽  
Philipp Frint ◽  
Martin Löbel ◽  
Thomas Lampke
Keyword(s):  
Tensile Strength ◽  
Grain Refinement ◽  
Spark Plasma Sintering ◽  
Equal Channel Angular Pressing ◽  
High Entropy Alloys ◽  
High Entropy ◽  
Fine Grained ◽  
Angular Pressing ◽  
Plasma Sintering ◽  
Spark Plasma

Single-phase, face-centered cubic (FCC) high-entropy alloys (HEA) are promising materials for future applications. In order to improve the mechanical properties, especially the tensile strength of these materials, this study focuses on the combination of spark plasma sintering (SPS) and equal-channel angular pressing (ECAP). The initial fine-grained microstructure produced by SPS is further refined by ECAP in a 90°-die. Optical microscopy and electron backscatter diffraction (EBSD) confirm this considerable grain refinement, leads to a grain size below 1 µm after 1 ECAP pass. An alternating arrangement of fine-grained areas and much coarser regions, aligned under an angle of approximately 27°, is found. Moreover, a first microstructural investigation of the twin structure is conducted. The mechanical behavior was investigated by hardness measurements and tensile testing. Both the hardness and tensile strength are remarkably increased after ECAP. In contrast, the uniform elongation and elongation at fracture are significantly reduced due to the strengthening mechanisms of strain hardening and grain refinement. It is concluded that the combination of SPS and ECAP is an attractive approach for designing (ultra)fine-grained HEAs with superior properties. The investigated techniques could be applied to understand the underlying microstructural mechanisms.

Microstructural and Mechanical Properties Enhancement in Ultrafine Grained Ni-Cr Alloy

2012 ◽  
Vol 1372 ◽  
Author(s):  
Kuk Hyun Song ◽  
Hye Jin Lee ◽  
Han Sol Kim ◽  
Won Yong Kim
Keyword(s):  
Mechanical Properties ◽  
Grain Refinement ◽  
Effective Strain ◽  
Initial Material ◽  
Grain Boundary Character ◽  
Ultrafine Grained ◽  
Processed Material ◽  
Average Grain Size ◽  
Ebsd Technique ◽  
Conventional Rolling

ABSTRACTThe present study was carried out to evaluate the microstructures and mechanical properties of severely deformed Ni-30Cr alloy. Cross-roll rolling (CRR) as severe plastic deformation (SPD) process was introduced and Ni-30Cr alloy sheets were cold rolled to a 90% thickness reduction and subsequently annealed at 700 °C for 30 min so as to obtain the recrystallized microstructure. For the analysis of grain boundary character distributions (GBCDs), electron back-scattered diffraction (EBSD) technique was introduced. CRR on Ni-30Cr alloy was effective to enhance the grain refinement through heat treatment; consequently, average grain size was significantly reduced from 33 μm in initial material to 0.6 μm in CRR processed material. This grain refinement directly affected the mechanical properties improvement, in which yield and tensile strengths were significantly increased than those of initial material. In this study, we systematically discussed the grain refinement, accompanying with increase in mechanical properties, in terms of the effective strain imposed by CRR, comparing with conventional rolling (CR).

scholarly journals Effects of Repetitive Upsetting Extrusion on the Microstructure and Texture of GWZK124 Alloy under Different Starting Temperatures

Materials ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2437
Author(s):  
Guanshi Zhang ◽  
Zhimin Zhang ◽  
Yingze Meng ◽  
Zhaoming Yan ◽  
Xin Che ◽  
...  
Keyword(s):  
Grain Size ◽  
Dynamic Recrystallization ◽  
Grain Refinement ◽  
Volume Fraction ◽  
Bimodal Microstructure ◽  
Continuous Dynamic Recrystallization ◽  
Average Grain Size ◽  
Second Phases ◽  
Continuous Dynamic ◽  
Weak Texture

The effects of repetitive upsetting extrusion under different starting temperatures on the microstructure and texture of GWZK124 alloy were investigated. The results clearly showed that the particles and second phases induced dynamic recrystallization (DRX), which can be explained by the particle-stimulated nucleation (PSN) mechanism. It was shown that grain refinement during repetitive upsetting extrusion (RUE) is dominated by a complicated combination of continuous dynamic recrystallization and discontinuous dynamic recrystallization. The RUEed alloys under different starting temperatures exhibited a bimodal microstructure comprising fine DRXed grains with weak texture and coarse deformed grains with strong texture. The DRXed grains could weaken the texture. As the RUE starting temperature decreased, the average grain size increased and the volume fraction of DRXed grains decreased.

Microstructure and Abrasion Resistance of Laser Cladding CoCrFeNiTiNbB1.25 High-Entropy Alloys Coatings Treated by Aging

2021 ◽  
Vol 13 (8) ◽  
pp. 1479-1487
Author(s):  
Lin Ding ◽  
Hongxin Wang ◽  
Xiumin Quan
Keyword(s):  
Abrasive Wear ◽  
Mass Loss ◽  
Laser Cladding ◽  
Aging Temperature ◽  
Abrasion Resistance ◽  
Volume Fraction ◽  
High Entropy Alloys ◽  
H13 Steel ◽  
High Entropy ◽  
The Right

Laser cladding CoCrFeNiTiNbB1.25 high-entropy alloys coatings on H13 steel was fabricated. The microstructure and abrasion resistance of aged high-entropy alloys coatings at different temperature were researched. Results showed the phase was not changed in the high-entropy alloys coatings as the aging temperature elevated, the volume fraction of TiB phase was firstly increased, then reduced. The diffraction peak of fcc phase was firstly shifted to the right, and then shifted to the left. The aged high-entropy alloys coatings consisted of typical dendrite, interdendritic eutectic and dispersed intermetallic compound, and the dendrite obviously was coarsened after aging at 850 °C. Compared with non-aged high-entropy alloys coatings, the microhardness of aged high-entropy alloys coatings was firstly elevated as the aging temperature elevated, then decreased, and the mass loss was opposite. The microhardness and mass loss was decreased by 4.3% and 11.9%, respectively, for the aging at 750 °C. The abrasion mechanism of non-aged high-entropy alloys coatings was the abrasive wear, and was the abrasive wear and adhesive wear after aging.

scholarly journals The Effect of Equal-Channel Angular Pressing on Microstructure, Mechanical Properties, and Biodegradation Behavior of Magnesium Alloyed with Silver and Gadolinium

Crystals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 918
Author(s):  
Boris Straumal ◽  
Natalia Martynenko ◽  
Diana Temralieva ◽  
Vladimir Serebryany ◽  
Natalia Tabachkova ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Grain Refinement ◽  
Equal Channel Angular Pressing ◽  
Fine Particles ◽  
Volume Fraction ◽  
Galvanic Corrosion ◽  
Angular Pressing ◽  
Average Grain Size ◽  
The Matrix ◽  
Mechanical Properties And Corrosion

The effect of equal channel angular pressing (ECAP) on the microstructure, texture, mechanical properties, and corrosion resistance of the alloys Mg-6.0%Ag and Mg-10.0%Gd was studied. It was shown that ECAP leads to grain refinement of the alloys down to the average grain size of 2–3 μm and 1–2 μm, respectively. In addition, in both alloys the precipitation of fine particles of phases Mg54Ag17 and Mg5Gd with sizes of ~500–600 and ~400–500 nm and a volume fraction of ~9% and ~8.6%, respectively, was observed. In the case of the alloy Mg-6.0%Ag, despite a significant grain refinement, a drop in the strength characteristics and a nearly twofold increase in ductility (up to ~30%) was found. This behavior is associated with the formation of a sharp inclined basal texture. For alloy Mg-10.0%Gd, both ductility and strength were enhanced, which can be associated with the combined effect of significant grain refinement and an increased probability of prismatic and basal glide. ECAP was also shown to cause a substantial rise of the biodegradation rate of both alloys and an increase in pitting corrosion. The latter effect is attributed to an increase in the dislocation density induced by ECAP and the occurrence of micro-galvanic corrosion at the matrix/particle interfaces.

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