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.

Microstructure and Mechanical Properties of W-High Entropy Alloy Composite by Hot Swaging

2021 ◽  
Vol 871 ◽  
pp. 3-8
Author(s):  
Rui Zhi Jian ◽  
Shang Cheng Zhou ◽  
Yun Fei Xue
Keyword(s):  
Mechanical Properties ◽  
Dynamic Compression ◽  
Axial Direction ◽  
High Entropy Alloy ◽  
Degree Of Deformation ◽  
High Entropy ◽  
The Matrix ◽  
Compression Yield Strength ◽  
Reduction In Area ◽  
Strengthening Method

To improve the mechanical properties of a sintered WHA using high entropy alloy as the matrix (W-HEA), investigations were carried out to apply deformation strengthening method of hot swaging on the W-HEA. The W-HEA samples were swaged around 1300°C with the 10%, 15% and 20% of reduction in area. The results show that the strength and hardness of the W-HEA composite increased with the increasing degree of deformation. And the aspect ratio of tungsten grains increases along the axial direction in the swaged alloys. The hardness of W-HEA with a 20% reduction in area reaches 448 HV, and the dynamic compression yield strength is about 1911 MPa. After hot swaging, the hardness and strength of the W-HEA are greatly improved compared with the sintered W-HEA.

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.

Effect of the Matrix and Reinforcement Sizes on the Microstructure, the Physical and Mechanical Properties of Al-SiC Composites

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
M. A. Salem ◽  
I. G. El-Batanony ◽  
M. Ghanem ◽  
Mohamed Ibrahim Abd ElAal
Keyword(s):  
Mechanical Properties ◽  
Powder Metallurgy ◽  
Volume Fraction ◽  
Physical And Mechanical Properties ◽  
Particle Sizes ◽  
Matrix Composites ◽  
Volume Fractions ◽  
The Matrix ◽  
Sic Composites ◽  
Sic Particle

Different Al-SiC metal matrix composites (MMCs) with a different matrix, reinforcement sizes, and volume fractions were fabricated using ball milling (BM) and powder metallurgy (PM) techniques. Al and Al-SiC composites with different volume fractions were milled for 120 h. Then, the Al and Al-SiC composites were pressed under 125 MPa and finally sintered at 450 °C. Moreover, microsize and combination between micro and nano sizes Al-SiC samples were prepared by the same way. The effect of the Al matrix, SiC reinforcement sizes and the SiC volume fraction on the microstructure evolution, physical and mechanical properties of the produced composites was investigated. The BM and powder metallurgy techniques followed by sintering produce fully dense Al-SiC composite samples with different matrix and reinforcement sizes. The SiC particle size was observed to have a higher effect on the thermal conductivity, electrical resistivity, and microhardness of the produced composites than that of the SiC volume fraction. The decreasing of the Al and SiC particle sizes and increasing of the SiC volume fraction deteriorate the physical properties. On the other hand, the microhardness was enhanced with the decreasing of the Al, SiC particle sizes and the increasing of the SiC volume fraction.

Microstructure and mechanical properties of AlCrFeCoNi high-entropy alloy particle reinforced Mg-9Al-1Zn matrix composites

2021 ◽  
Vol 112 (7) ◽  
pp. 538-545
Author(s):  
Yongsheng Chen ◽  
Zesheng Ji ◽  
Maoliang Hu ◽  
Hongyu Xu ◽  
Guangjie Feng
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Volume Fraction ◽  
Dominant Role ◽  
Particle Volume Fraction ◽  
Stress Transfer ◽  
High Entropy Alloy ◽  
Compression Tests ◽  
Particle Volume ◽  
High Entropy

Abstract AlCrFeCoNi particles were added to Mg-9Al-1Zn alloy in a rotary blowing process. The microstructures and mechanical properties of Mg-9Al-1Zn based composites were characterized by means of X-ray diffraction, optical microscopy, scanning electron microscopy, transmission electron microscopy, and tensile and compression tests at room temperature. Results revealed that AlCrFeCoNi particles could effectively refine the grains, and the rotary blowing process enabled the uniform distribution of these particles. The mechanical properties of composites improved with the increase of particle volume fraction. The superior wettability of AlCrFeCoNi particles supported their reliable bonding with the Mg-9Al-1Zn matrix. The Hall–Petch strengthening and stress transfer effect played a dominant role in the improvement of compressive and tensile properties.

scholarly journals Hexagonal Closed-Packed Precipitation Enhancement in a NbTiHfZr Refractory High-Entropy Alloy

Metals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 485 ◽  
Author(s):  
Yueli Ma ◽  
Shiwei Wu ◽  
Yuefei Jia ◽  
Pengfei Hu ◽  
Yeqiang Bu ◽  
...  
Keyword(s):  
Volume Fraction ◽  
High Strength ◽  
High Entropy Alloy ◽  
Body Centered Cubic ◽  
Ductility Property ◽  
High Entropy ◽  
New Strategy ◽  
Precipitation Enhancement ◽  
Strength And Ductility ◽  
Hexagonal Closed Packed

A NbTiHfZr high-entropy alloy (HEA) with a main phase of body-centered cubic structure is fabricated. Some hexagonal closed-packed (hcp) precipitates are observed in this alloy. A thermal-mechanical process, i.e., cold-rolling followed by annealing, can manipulate the volume fraction of the hcp nano-precipitates that can enhance strength and ductility. The enhancement is tailorable as a function of the volume fraction of the hcp nano-precipitate. The results indicate that the strength-ductility property can be manipulated via adjusting post-deformation heat-treatment methods, which provide a new strategy by utilizing metastability at high-temperature to design high strength refractory HEAs (RHEAs) without lost in ductility.

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.

Microstructural Evolution and Mechanical Properties in a Mn1.05Fe1.05CoNiCu0.9 High Entropy Alloy

2017 ◽  
Vol 737 ◽  
pp. 44-49 ◽  
Author(s):  
Seung Min Oh ◽  
Sun Ig Hong
Keyword(s):  
Mechanical Properties ◽  
Single Phase ◽  
Cast Alloy ◽  
High Entropy Alloy ◽  
Microstructural Stability ◽  
Dendrite Structure ◽  
High Entropy ◽  
Melting Temperatures ◽  
The Matrix ◽  
Fcc Structure

In the present study, the microstructural stability and mechanical properties of a MnFeCoNiCu alloy in which Cr was replaced by Cu from Cantor composition (CoCrFeMnNi) was studied. In the as-cast alloy, the dendrite arms are enriched with Cu and Mn and matrix between dendrite arms is enriched with Fe and Co. Ni was richer in the matrix, but also observed in the dendrite arms. Cu and Mn tend to segregate and solidify initially because the melting temperatures of Cu and Mn are lower than Fe and Co, resulting in the growth of Cu-Mn dendrite. After homogenization, the dendrites structure disappeared and grain boundaries are visible, indicating the segregated elements in the dendrite structure were homogenized. The presence of single phase FCC structure was confirmed after homogenization. The tensile strength of 1220 MPa with the ductility of 6 % was obtained in MnFeCoNiCu alloy.

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