scholarly journals Microstructure and Mechanical Property Evolution during Annealing of a Cold-Rolled Metastable Powder Metallurgy High Entropy Alloy

Entropy ◽  
2019 ◽  
Vol 21 (9) ◽  
pp. 833 ◽  
Author(s):  
Li ◽  
Qiu ◽  
Guo ◽  
Liu ◽  
Zhou ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Mechanical Property ◽  
Tensile Strength ◽  
Powder Metallurgy ◽  
Cold Deformation ◽  
Precipitation Strengthening ◽  
High Entropy Alloy ◽  
Σ Phase ◽  
High Entropy ◽  
Fine Grain

Precipitation strengthening is an effective approach to strengthen high-entropy alloys (HEAs) with a simple face-center-cubic (FCC) structure. In this work, CoCrFeNiMo0.2 HEAs were prepared by powder metallurgy, followed by cool rolling and subsequent heat-treatment at different temperatures. The effects of cold working and annealing on microstructure and mechanical properties have been investigated. Results show the fine and dispersed (Cr, Mo)-rich σ phase with a topologically close-packed structure precipitated in the FCC matrix after the prior cold deformation process, which enhanced the mechanical property of the CoCrFeNiMo0.2 alloy. The HEA annealed at 600 °C for 48 h had a tensile strength of 1.9 GPa but an elongation which decreased to 8%. The HEA annealed at 800 °C for 12 h exhibited a tensile strength of 1.2 GPa and an elongation of 31%. These outstanding mechanical properties can be attributed to precipitation strengthening and fine-grain strengthening.

Influence of alumina whisker or nano-carbon contents on the microstructure and mechanical properties of CuZrTiAlNi refractory high entropy alloy composites

2020 ◽  
Vol 62 (7) ◽  
pp. 678-688
Author(s):  
X. Jiang ◽  
J. Chen ◽  
H. Sun ◽  
Z. Shao
Keyword(s):  
Mechanical Properties ◽  
Load Transfer ◽  
Microwave Sintering ◽  
Fracture Morphology ◽  
Strengthening Mechanism ◽  
Cold Isostatic Pressing ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Structure And Property ◽  
Fine Grain

Abstract High-entropy alloy composites were fabricated by ball milling, cold isostatic pressing and microwave sintering to which were added varied contents of Al2O3 whiskers, La-Ce, and carbon nanotubes-graphene, respectively. The structure and mechanical properties of the composites were investigated by X-ray diffraction, scanning electron microscopy and a microhardness tester. The high-entropy alloy and composites show amorphous phases and some crystalline phases. Accordingly, the addition of the reinforcement phase can refine the grain size. The formation mechanism of the phase is mainly related to the factors of mixing entropy, enthalpy, differences in atomic size, and the structure and property of the elements. The hardness of the composites is higher than that of the alloy (437.5 HV), and those composites reinforced by 0.5 wt.-% nanotubes- 0.5 wt.-% graphene are the highest (593.99 HV). The fracture morphology of the Al2O3 whisker reinforced composite shows a river pattern, indicating brittle cleavage. According to the research results, it can be concluded that the strengthening mechanism of the high entropy alloy composites mainly reflects fine grain strengthening and load transfer, and the toughening mechanism mainly crack bridging and a pulling out of the reinforcing phase.

scholarly journals Effects of Annealing on Microstructure and Mechanical Properties of Metastable Powder Metallurgy CoCrFeNiMo0.2 High Entropy Alloy

Entropy ◽  
2019 ◽  
Vol 21 (5) ◽  
pp. 448 ◽  
Author(s):  
Cui Zhang ◽  
Bin Liu ◽  
Yong Liu ◽  
Qihong Fang ◽  
Wenmin Guo ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Powder Metallurgy ◽  
Volume Fraction ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Large Volume Fraction ◽  
The Matrix ◽  
Coarse Precipitation ◽  
Precipitation Enhancement ◽  
Precipitation Phase

A CoCrFeNiMo0.2 high entropy alloy (HEA) was prepared through powder metallurgy (P/M) process. The effects of annealing on microstructural evolution and mechanical properties of P/M HEAs were investigated. The results show that the P/M HEA exhibit a metastable FCC single-phase structure. Subsequently, annealing causes precipitation in the grains and at the grain boundaries simultaneously. As the temperature increases, the size of the precipitates grows, while the content of the precipitates tends to increase gradually first, and then decrease as the annealing temperature goes up to 1000 °C. As the annealing time is prolonged, the size and content of the precipitates gradually increases, eventually reaching a saturated stable value. The mechanical properties of the annealed alloys have a significant correspondence with the precipitation behavior. The larger the volume fraction and the size of the precipitates, the higher the strength and the lower the plasticity of the HEA. The CoCrFeNiMo0.2 high entropy alloy, which annealed at 800 °C for 72 h, exhibited the most excellent mechanical properties with the ultimate tensile strength of about 850 MPa and an elongation of about 30%. Nearly all of the annealed HEAs exhibit good strength–ductility combinations due to the significant precipitation enhancement and nanotwinning. The separation of the coarse precipitation phase and the matrix during the deformation process is the main reason for the formation of micropores. Formation of large volume fraction of micropores results in a decrease in the plasticity of the alloy.

A Powder-Metallurgy-Based Fabrication Route Towards Achieving High Tensile Strength with Ultra-High Ductility in High-Entropy Alloy

2020 ◽  
Author(s):  
Peyman Asghari-Rad ◽  
Praveen Sathiyamoorthi ◽  
Nhung Thi-Cam Nguyen ◽  
Alireza Zargaran ◽  
Taek Soo Kim ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Powder Metallurgy ◽  
High Entropy Alloy ◽  
High Ductility ◽  
High Tensile Strength ◽  
High Entropy

scholarly journals Evolution of Microstructure and Mechanical Properties of LM25–HEA Composite Processed through Stir Casting with a Bottom Pouring System

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 230
Author(s):  
Mekala Chinababu ◽  
Nandivelegu Naga Krishna ◽  
Katakam Sivaprasad ◽  
Konda Gokuldoss Prashanth ◽  
Eluri Bhaskara Rao
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Tensile Strength ◽  
Aluminum Matrix ◽  
Stir Casting ◽  
Significant Loss ◽  
Aluminum Matrix Composites ◽  
High Entropy Alloy ◽  
High Entropy ◽  
The Matrix

Aluminum matrix composites reinforced by CoCrFeMnNi high entropy alloy (HEA) particulates were fabricated using the stir casting process. The as-cast specimens were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). The results indicated that flake-like silicon particles and HEA particles were distributed uniformly in the aluminum matrix. TEM micrographs revealed the presence of both the matrix and reinforcement phases, and no intermetallic phases were formed at the interface of the matrix and reinforcement phases. The mechanical properties of hardness and tensile strength increased with an increase in the HEA content. The Al 6063–5 wt.% HEA composite had a ultimate tensile strength (UTS) of approximately 197 MPa with a reasonable ductility (around 4.05%). The LM25–5 wt.% HEA composite had a UTS of approximately 195 Mpa. However, the percent elongation decreased to roughly 3.80%. When the reinforcement content increased to 10 wt.% in the LM25 composite, the UTS reached 210 MPpa, and the elongation was confined to roughly 3.40%. The fracture morphology changed from dimple structures to cleavage planes on the fracture surface with HEA weight percentage enhancement. The LM25 alloy reinforced with HEA particles showed enhanced mechanical strength without a significant loss of ductility; this composite may find application in marine and ship building industries.

A powder-metallurgy-based fabrication route towards achieving high tensile strength with ultra-high ductility in high-entropy alloy

2021 ◽  
Vol 190 ◽  
pp. 69-74 ◽  
Author(s):  
Peyman Asghari-Rad ◽  
Praveen Sathiyamoorthi ◽  
Nhung Thi-Cam Nguyen ◽  
Alireza Zargaran ◽  
Taek Soo Kim ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Powder Metallurgy ◽  
High Entropy Alloy ◽  
High Ductility ◽  
High Tensile Strength ◽  
High Entropy
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