scholarly journals The Effect of Al on the Formation of a CrTaO4 Layer in Refractory High Entropy Alloys Ta-Mo-Cr-Ti-xAl

2021 ◽  
Author(s):  
S. Schellert ◽  
B. Gorr ◽  
H.- J. Christ ◽  
C. Pritzel ◽  
S. Laube ◽  
...  
Keyword(s):  
Mass Gain ◽  
Positive Influence ◽  
High Entropy Alloys ◽  
Oxide Scales ◽  
Temperature Oxidation ◽  
Internal Corrosion ◽  
High Entropy ◽  
Continuous Mass ◽  
Oxide Substrate ◽  
Kinetics Of

AbstractIn this study, the effect of Al on the high temperature oxidation of Al-containing refractory high entropy alloys (RHEAs) Ta-Mo-Cr-Ti-xAl (x = 5; 10; 15; 20 at%) was examined. Oxidation experiments were performed in air for 24 h at 1200 °C. The oxidation kinetics of the alloy with 5 at% Al is notably affected by the formation of gaseous MoO3 and CrO3, while continuous mass gain was detected for alloys with the higher Al concentrations. The alloys with 15 and 20 at% Al form relatively thin oxide scales and a zone of internal corrosion due to the formation of dense CrTaO4 scales at the interface oxide/substrate. The alloys with 5 and 10 at% Al exhibit, on the contrary, thick and porous oxide scales because of fast growing Ta2O5. The positive influence of Al on the formation of Cr2O3 followed by the growth of CrTaO4 to yield a compact scale is explained by getter and nucleation effects.

Effect of Compressive Stress on the High-Temperature Oxidation Behavior of a Fe-20Ni Alloy in Air

2018 ◽  
Vol 921 ◽  
pp. 168-176
Author(s):  
Chang Hai Zhou ◽  
Rui Yun Pan ◽  
Hai Tao Ma
Keyword(s):  
Compressive Stress ◽  
High Temperature Oxidation ◽  
Oxidation Behavior ◽  
Oxide Scales ◽  
External Scale ◽  
X Ray Diffraction ◽  
Temperature Oxidation ◽  
X Ray ◽  
High Temperature Oxidation Behavior ◽  
Kinetics Of

The oxidation behavior of Fe-20Ni alloy under compressive stress in air was studied at 800, 900 °C. The results examined by using scanning electron microscope (SEM) and X-ray diffraction (XRD) indicates that the oxide scales were consisted of an external scale and a subscale which has an intragranular scale (above 5 h at 800 °C and 900 °C) and an intergranular scale. Compared with the unstressed specimen, the growth kinetics of external scale was accelerated by an applied compressive stress. Besides, the compressive stress induced an increase in the growths of intragranular scale and intergranular scale formed on the specimens oxidized at 900 °C. However, the effect of compressive stress on the growth of intergranular scale and intragranular scale was not obvious in the case of 800°C. In addition, cracks developed in the subscale for the specimens oxidized under 2.5 MPa compressive stress when the oxidation time exceeded 20 h.

scholarly journals Thermodynamics and Kinetics of High-Entropy Alloys

2021 ◽  
Author(s):  
Michael C. Gao ◽  
Raymundo Arróyave ◽  
John E. Morral ◽  
Ursula R. Kattner
Keyword(s):  
High Entropy Alloys ◽  
High Entropy ◽  
Thermodynamics And Kinetics ◽  
Kinetics Of

scholarly journals Effect of V and Ti on the Oxidation Resistance of WMoTaNb Refractory High-Entropy Alloy at High Temperatures

Metals ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 41
Author(s):  
Shuaidan Lu ◽  
Xiaoxiao Li ◽  
Xiaoyu Liang ◽  
Wei Yang ◽  
Jian Chen
Keyword(s):  
Oxidation Resistance ◽  
High Temperatures ◽  
Elevated Temperatures ◽  
Early Stage ◽  
Mass Gain ◽  
High Entropy Alloy ◽  
High Entropy Alloys ◽  
X Ray Diffraction ◽  
X Ray ◽  
High Entropy

Alloying with V and Ti elements effectively improves the strength of WMoTaNb refractory high entropy alloys (RHEAs) at elevated temperatures. However, their effects on the oxidation resistance of WMoTaNb RHEAs are unknown, which is vitally important to their application at high temperatures. In this work, the effect of V and Ti on the oxidation behavior of WMoTaNb RHEA at 1000 °C was investigated using a thermogravimetric system, X-ray diffraction and scanning electron microscopy. The oxidation of all alloys was found to obey a power law passivating oxidation at the early stage. The addition of V aggravates the volatility of V2O5, MoO3 and WO3, and leads to disastrous internal oxidation. The addition of Ti reduces the mass gain in forming the full coverage of passivating scale and prolongs the passivation duration of alloys.

High Compressibility ZrTiHfV0.5Nb0.5CX Refractory High-Entropy Alloys

2019 ◽  
Vol 944 ◽  
pp. 163-168
Author(s):  
Wen Kai Chen ◽  
Yun Kai Li ◽  
Yi Wen Chen
Keyword(s):  
High Temperature ◽  
High Entropy Alloys ◽  
High Melting Point ◽  
Temperature Oxidation ◽  
High Entropy ◽  
Arc Melting ◽  
Eds Analysis ◽  
Promising Application ◽  
Bcc Phase ◽  
High Temperature Compressive Strength

Refractory high-entropy alloys (RHEAs) have outstanding characteristics such as high melting point, high temperature oxidation resistance and corrosion resistance, which shows very promising application in the high temperature field; but commonly the refractory high-entropy alloys have the disadvantages of high density and poor plasticity. In this work, ZrTiHfV0.5Nb0.5Cx(x=0, 0.06, 0.12, 0.2) alloys are prepared by vacuum non-consumable arc-melting with ZrTiHfV0.5Nb0.5based. The density of ZrTiHfV0.5Nb0.5C0.2alloy is reduced to 8.014g/cm3compared to ZrTiHfV0.5Nb0.5(8.135g/cm3). The microstructure, static and high-temperature compressive strength are investigated. XRD and EDS analysis show that the microstructure of ZrTiHf0.5Nb0.5Cxalloys consists of BCC phase and HfC phase. ZrTiHfV0.5Nb0.5Cxalloys have high compression plasticity with plastic strain> 40% at room temperature, no fracture occurred during compression and yield stress is closed to 1GPa.

High-Temperature Oxidation Behavior of AlxCoCrFeNiM (M = Cu, Ti, V) High-Entropy Alloys

2021 ◽  
Vol 24 (6) ◽  
pp. 653-662
Author(s):  
N. A. Shaburova ◽  
A. Ostovari Moghaddam ◽  
S. N. Veselkov ◽  
M. V. Sudarikov ◽  
O. V. Samoilova ◽  
...  
Keyword(s):  
High Temperature ◽  
High Temperature Oxidation ◽  
Oxidation Behavior ◽  
High Entropy Alloys ◽  
Temperature Oxidation ◽  
High Entropy ◽  
High Temperature Oxidation Behavior

High-Temperature Oxidation Behavior of Fe-Si-Ce Alloys

2016 ◽  
Vol 35 (2) ◽  
pp. 177-183 ◽  
Author(s):  
Yong Su ◽  
Shunke Zhang ◽  
Guangyan Fu ◽  
Qun Liu ◽  
Yuanze Tang
Keyword(s):  
Grain Size ◽  
Oxidation Behavior ◽  
Oxidation Mechanism ◽  
Mass Gain ◽  
Optical Microscope ◽  
Oxide Scales ◽  
Temperature Oxidation ◽  
Beneficial Effects ◽  
Negative Effect ◽  
High Temperature Oxidation Behavior

AbstractThe oxidation behavior of Fe-Si-Ce alloys with different Ce content at 1,173 and 1,273 K has been studied by means of optical microscope (OM), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscope (SEM). Results show that the Ce addition refines the grain size of Fe-Si alloys, and correspondingly the grain size of the oxides decreases, which increases the grain boundary concentration and promotes the short-path diffusion of the alloying elements and oxygen. During oxidation, the positive effect of the grain refinement on the oxidation behavior of the alloy is more obvious than negative effect, so the Ce addition improves the oxidation resistances of the Fe-3Si alloys. Compared to Fe-3Si-0.5Ce alloy, Fe-3Si-5.0Ce alloy has the larger mass gain for the preferential oxidation of the excessive content of Ce exceeding its beneficial effects. The rare earth Ce changes the oxidation mechanism of Fe-Si alloys. Oxygen penetrates the oxide scales and reacts preferentially with Ce-rich phases, which results in the pinning effect and improves the adhesion of the oxide scales.

scholarly journals Kinetic ways of tailoring phases in high entropy alloys

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Feng He ◽  
Zhijun Wang ◽  
Yiyan Li ◽  
Qingfeng Wu ◽  
Junjie Li ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Equilibrium Phase ◽  
High Entropy Alloys ◽  
Kinetic Effect ◽  
Phase Selection ◽  
High Entropy ◽  
Comprehensive Performance ◽  
Sluggish Diffusion ◽  
Kinetics Of ◽  
Theoretical Analyses

Abstract The comprehensive performance of high entropy alloys (HEAs) depends on the phase selection significantly. However, up to now, investigations of the phase selection in HEAs mainly focused on the thermodynamic equilibrium phase, while kinetic ways of tailoring the phases in HEAs are seldom considered. In HEAs, the kinetics of sluggish diffusion and the numerous possible phases make the kinetics of phase transformation more complex and intriguing. Here, the kinetic effect in CoCrFeNiTi0.4 HEAs was investigated to reveal the possibility of controlling phase selection via kinetic ways for HEAs. The σ, γ′ and R phases in the CoCrFeNiTi0.4 HEA can be controlled under different cooling rate both in solidification and solid transformation. The theoretical analyses revealed the kinetic effect on phase selection. The method proposed here, tailoring the phases with different kinetic ways, could be used to prepare promising HEAs with very rich composition design.

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