scholarly journals Impact of Chemical Fluctuations on Stacking Fault Energies of CrCoNi and CrMnFeCoNi High Entropy Alloys from First Principles

Entropy ◽  
2018 ◽  
Vol 20 (9) ◽  
pp. 655 ◽  
Author(s):  
Yuji Ikeda ◽  
Fritz Körmann ◽  
Isao Tanaka ◽  
Jörg Neugebauer
Keyword(s):  
Mechanical Properties ◽  
First Principles ◽  
Mechanical Performance ◽  
Stacking Faults ◽  
Stacking Fault ◽  
High Entropy Alloys ◽  
Face Centered Cubic ◽  
High Entropy ◽  
Linear Behavior ◽  
The Impact

Medium and high entropy alloys (MEAs and HEAs) based on 3d transition metals, such as face-centered cubic (fcc) CrCoNi and CrMnFeCoNi alloys, reveal remarkable mechanical properties. The stacking fault energy (SFE) is one of the key ingredients that controls the underlying deformation mechanism and hence the mechanical performance of materials. Previous experiments and simulations have therefore been devoted to determining the SFEs of various MEAs and HEAs. The impact of local chemical environment in the vicinity of the stacking faults is, however, still not fully understood. In this work, we investigate the impact of the compositional fluctuations in the vicinity of stacking faults for two prototype fcc MEAs and HEAs, namely CrCoNi and CrMnFeCoNi by employing first-principles calculations. Depending on the chemical composition close to the stacking fault, the intrinsic SFEs vary in the range of more than 150 mJ/m 2 for both the alloys, which indicates the presence of a strong driving force to promote particular types of chemical segregations towards the intrinsic stacking faults in MEAs and HEAs. Furthermore, the dependence of the intrinsic SFEs on local chemical fluctuations reveals a highly non-linear behavior, resulting in a non-trivial interplay of local chemical fluctuations and SFEs. This sheds new light on the importance of controlling chemical fluctuations via tuning, e.g., the annealing condition to obtain the desired mechanical properties for MEAs and HEAs.

Synergetic effect of Si addition on mechanical properties in face-centered-cubic high entropy alloys: A first-principles study

2021 ◽  
Author(s):  
T Tsuru ◽  
Ivan Lobzenko ◽  
Daixiu Wei
Keyword(s):  
Mechanical Properties ◽  
First Principles ◽  
Stacking Fault ◽  
High Entropy Alloys ◽  
Face Centered Cubic ◽  
High Entropy ◽  
Si Doped ◽  
Face Centered ◽  
Si Addition ◽  
Strength And Ductility

Abstract High-entropy alloys (HEA) have been receiving increased attention for their excellent mechanical properties. Our recent study revealed that Si-doped face-centered cubic (FCC) HEAs have great potential to improve both strength and ductility. Here, we carried out first-principles calculations in cooperation with Monte Carlo simulation and structural factor analysis to explore the effect of Si addition on the macroscopic mechanical properties. As a result, Si addition increased the local lattice distortion and the stacking fault energy. Furthermore, the short-range order formation in Si-doped alloy caused highly fluctuated stacking fault energy. Thus, the heterogeneous solid solution states in which low and high stacking fault regions are distributed into the matrix were nucleated. This unique feature in Si-doped FCC-HEA induces ultrafine twin formation in Si-doped alloys, which can be a dominant factor in improving both strength and ductility.

scholarly journals Effects of Different Contents of Each Component on the Structural Stability and Mechanical Properties of Co-Cr-Fe-Ni High-Entropy Alloys

2021 ◽  
Vol 11 (6) ◽  
pp. 2832
Author(s):  
Haibo Liu ◽  
Cunlin Xin ◽  
Lei Liu ◽  
Chunqiang Zhuang
Keyword(s):  
Mechanical Properties ◽  
Structural Stability ◽  
High Entropy Alloys ◽  
Face Centered Cubic ◽  
Obvious Effect ◽  
High Entropy ◽  
Precise Control ◽  
Component Content ◽  
Face Centered ◽  
And Performance

The structural stability of high-entropy alloys (HEAs) is closely related to their mechanical properties. The precise control of the component content is a key step toward understanding their structural stability and further determining their mechanical properties. In this study, first-principle calculations were performed to investigate the effects of different contents of each component on the structural stability and mechanical properties of Co-Cr-Fe-Ni HEAs based on the supercell model. Co-Cr-Fe-Ni HEAs were constructed based on a single face-centered cubic (FCC) solid solution. Elemental components have a clear effect on their structure and performance; the Cr and Fe elements have an obvious effect on the structural stability and equilibrium lattice constant, respectively. The Ni elements have an obvious effect on stiffness. The Pugh ratios indicate that Cr and Ni addition may increase ductility, whereas Co and Fe addition may decrease it. With increasing Co and Fe contents or decreasing Cr and Ni contents, the structural stability and stiffness of Co-Cr-Fe-Ni HEAs are improved. The structural stability and mechanical properties may be related to the strength of the metallic bonding and covalent bonding inside Co-Cr-Fe-Ni HEAs, which, in turn, is determined by the change in element content. Our results provide the underlying insights needed to guide the optimization of Co-Cr-Fe-Ni HEAs with excellent mechanical properties.

Effect of Interstitial Elements on the Cryogenic Mechanical Behavior of FCC High Entropy Alloys

2021 ◽  
Vol 1016 ◽  
pp. 1386-1391
Author(s):  
Anastasia Semenyuk ◽  
Margarita Klimova ◽  
Sergey Zherebtsov ◽  
Nikita Stepanov
Keyword(s):  
Mechanical Properties ◽  
Solid Solution ◽  
Thermomechanical Processing ◽  
Induction Melting ◽  
High Entropy Alloys ◽  
Strengthening Effect ◽  
Face Centered Cubic ◽  
High Entropy ◽  
C And N ◽  
Interstitial Elements

High entropy alloys (HEAs) with face-centered cubic (fcc) structure, namely equiatomic CoCrFeMnNi alloy, have attracted considerable attention because of impressive cryogenic mechanical properties – strength, ductility, and fracture toughness. Further increase of the properties can be achieved, for example, by proper alloying. A particularly attractive option is the addition of interstitial elements like carbon or nitrogen. In present work, a series of CoCrFeMnNi-based alloys with different amounts of C and N (0-2 at.%) was prepared by induction melting. The alloys doped with C had lower Cr content to increase the solubility of carbon in the fcc solid solution. It was revealed that the solid solution strengthening effect of both C and N is significantly increased when the testing temperature decreases from 293K to 77K. The effect of thermomechanical processing on the structure and mechanical properties of the alloys is analyzed.

scholarly journals Additive Manufacturing of High-Entropy Alloys: A Review

Entropy ◽  
2018 ◽  
Vol 20 (12) ◽  
pp. 937 ◽  
Author(s):  
Shuying Chen ◽  
Yang Tong ◽  
Peter Liaw
Keyword(s):  
Mechanical Properties ◽  
Additive Manufacturing ◽  
High Efficiency ◽  
Mechanical Performance ◽  
Heating Temperature ◽  
Intermetallic Phase ◽  
Solid Solution Phase ◽  
High Entropy Alloys ◽  
Scanning Method ◽  
High Entropy

Owing to the reduced defects, low cost, and high efficiency, the additive manufacturing (AM) technique has attracted increasingly attention and has been applied in high-entropy alloys (HEAs) in recent years. It was found that AM-processed HEAs possess an optimized microstructure and improved mechanical properties. However, no report has been proposed to review the application of the AM method in preparing bulk HEAs. Hence, it is necessary to introduce AM-processed HEAs in terms of applications, microstructures, mechanical properties, and challenges to provide readers with fundamental understanding. Specifically, we reviewed (1) the application of AM methods in the fabrication of HEAs and (2) the post-heat treatment effect on the microstructural evolution and mechanical properties. Compared with the casting counterparts, AM-HEAs were found to have a superior yield strength and ductility as a consequence of the fine microstructure formed during the rapid solidification in the fabrication process. The post-treatment, such as high isostatic pressing (HIP), can further enhance their properties by removing the existing fabrication defects and residual stress in the AM-HEAs. Furthermore, the mechanical properties can be tuned by either reducing the pre-heating temperature to hinder the phase partitioning or modifying the composition of the HEA to stabilize the solid-solution phase or ductile intermetallic phase in AM materials. Moreover, the processing parameters, fabrication orientation, and scanning method can be optimized to further improve the mechanical performance of the as-built-HEAs.

scholarly journals CrMnFeCoNi high entropy alloys with carbon and nitrogen: mechanical properties, wear and corrosion resistance

2021 ◽  
Vol 3 (11) ◽  
Author(s):  
L. Chmielak ◽  
L. Mujica Roncery ◽  
P. Niederhofer ◽  
S. Weber ◽  
W. Theisen
Keyword(s):  
Mechanical Properties ◽  
Corrosion Resistance ◽  
Austenitic Steels ◽  
High Entropy Alloys ◽  
Interstitial Free ◽  
High Entropy ◽  
Carbon And Nitrogen ◽  
Wear And Corrosion ◽  
Wear And Corrosion Resistance ◽  
The Impact

AbstractThe use of interstitial elements has been a key factor for the development of different kinds of steels. However, this aspect has been little explored in the field of high entropy alloys (HEAs). In this investigation, the effect of carbon and nitrogen in a near-equiatomic CrMnFeCoNi HEA is studied, analyzing their impact on the microstructure, and mechanical properties from 77K to 673K, as well as wear, and corrosion resistance. Carbon and nitrogen are part of the FCC solid solution and contribute to the formation of precipitates. An increase in the yield and ultimate tensile strength accompanied with a decrease in the ductility are the main effects of C and N. The impact toughness of the interstitial-free material is higher than that of C and C+N alloyed systems. Compared to CrNi and CrMn austenitic steels, the wear resistance of the alloys at room temperature is rather low. The surface corrosion resistance of HEAs is comparable to austenitic steels; nevertheless HEAs are more susceptible to pitting in chloride containing solutions.

scholarly journals Generalized Stacking Fault Energy of Al-Doped CrMnFeCoNi High-Entropy Alloy

Nanomaterials ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 59 ◽  
Author(s):  
Xun Sun ◽  
Hualei Zhang ◽  
Wei Li ◽  
Xiangdong Ding ◽  
Yunzhi Wang ◽  
...  
Keyword(s):  
Interfacial Energy ◽  
Stacking Fault ◽  
Stacking Fault Energy ◽  
High Entropy Alloy ◽  
High Entropy Alloys ◽  
Face Centered Cubic ◽  
High Entropy ◽  
Al Content ◽  
Generalized Stacking Fault ◽  
Generalized Stacking Fault Energy

Using first-principles methods, we investigate the effect of Al on the generalized stacking fault energy of face-centered cubic (fcc) CrMnFeCoNi high-entropy alloy as a function of temperature. Upon Al addition or temperature increase, the intrinsic and extrinsic stacking fault energies increase, whereas the unstable stacking fault and unstable twinning fault energies decrease monotonously. The thermodynamic expression for the intrinsic stacking fault energy in combination with the theoretical Gibbs energy difference between the hexagonal close packed (hcp) and fcc lattices allows one to determine the so-called hcp-fcc interfacial energy. The results show that the interfacial energy is small and only weakly dependent on temperature and Al content. Two parameters are adopted to measure the nano-twinning ability of the present high-entropy alloys (HEAs). Both measures indicate that the twinability decreases with increasing temperature or Al content. The present study provides systematic theoretical plasticity parameters for modeling and designing high entropy alloys with specific mechanical properties.

Ultrastrong Al0.1CoCrFeNi high-entropy alloys at small scales: effects of stacking faults vs. nanotwins

Nanoscale ◽  
2018 ◽  
Vol 10 (28) ◽  
pp. 13329-13334 ◽  
Author(s):  
Xiaobin Feng ◽  
Jinyu Zhang ◽  
Kai Wu ◽  
Xiaoqing Liang ◽  
Gang Liu ◽  
...  
Keyword(s):  
Stacking Faults ◽  
Maximum Strength ◽  
High Entropy Alloy ◽  
High Entropy Alloys ◽  
Face Centered Cubic ◽  
High Entropy ◽  
Small Scales ◽  
Face Centered

The present stacking faulted and nanotwinned Al0.1CoCrFeNi high-entropy alloy pillars achieved the maximum strength among face-centered cubic structured metals.

Stacking fault energy of face-centered-cubic high entropy alloys

2018 ◽  
Vol 93 ◽  
pp. 269-273 ◽  
Author(s):  
S.F. Liu ◽  
Y. Wu ◽  
H.T. Wang ◽  
J.Y. He ◽  
J.B. Liu ◽  
...  
Keyword(s):  
Stacking Fault ◽  
Stacking Fault Energy ◽  
High Entropy Alloys ◽  
Face Centered Cubic ◽  
High Entropy ◽  
Face Centered
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