scholarly journals The Effect of Ge Addition on the Oxidation of Nb-24Ti-18Si Silicide Based Alloys

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3120 ◽  
Author(s):  
Zifu Li ◽  
Panos Tsakiropoulos
Keyword(s):  
Oxidation Resistance ◽  
Refractory Metal ◽  
Isothermal Oxidation ◽  
Oxidation Behaviour ◽  
The Other ◽  
High Entropy Alloys ◽  
High Entropy ◽  
Parabolic Kinetics ◽  
Cast Alloys ◽  
Oxidation In Air

In this paper, we report research about the isothermal oxidation in air at 800 and 1200 °C for 100 h of the as-cast alloys (at.%) Nb-18Si-5Ge (ZF1), Nb-18Si-10Ge (ZF2), Nb-24Ti-18Si-5Ge (ZF3), Nb-24Ti-18Si-5Cr (ZF4), Nb-24Ti-18Si-5Al (ZF5), Nb-24Ti-18Si-5Al-5Cr-5Ge (ZF6), and Nb-24Ti-18Si-5Al-5Cr-5Ge-5Hf (ZF9), the microstructures of which were reported in previous publications. Only the alloys ZF1, ZF2, and ZF3 suffered from pest oxidation at 800 °C. The Ge addition substantially improved the oxidation resistance of the other alloys both at 800 °C and 1200 °C, which followed parabolic kinetics at 800 °C and in the early stages at 1200 °C and linear kinetics at longer times, where there was spallation of the scales. The Nb2O5 and TiNb2O7 oxides were formed in the scales of the alloys ZF4, ZF5, ZF6, and ZF9 at 800 °C and 1200 °C, the GeO2 was observed in all scales and the SiO2 in the scales of the alloys ZF4 and ZF5, the CrNbO4 in the scales of the alloys ZF4, ZF6, and ZF9 and the AlNbO4 in the scales of the alloys ZF5, ZF6, and ZF9. Diffusion zones were formed below the scale/substrate interface only in the alloys ZF4 and ZF5 where the Nbss and Nb5Si3 were contaminated by oxygen. However, these phases were not contaminated by oxygen in the bulk of the alloys ZF4, ZF5, ZF6, and ZF9. The alloys ZF9 and ZF6 exhibited the best oxidation behaviour at 800 °C and 1200 °C, respectively. The alloys were compared with Nb-silicide based alloys of similar compositions without Ge and Hf additions and the alloy ZF9 with refractory metal High Entropy Alloys. Compared with the former alloys, the addition of Ge reduced the vol % of the Nbss. Compared with the latter alloys, the superior oxidation behaviour of the alloy ZF9 was attributed to its higher and lower values respectively of the parameters δ and VEC.

scholarly journals Deciphering the role of Al2O3 formed during isothermal oxidation in a dual-phase AlCoCrFeNi2.1 Eutectic High-Entropy Alloy

2021 ◽  
Author(s):  
Mainak Saha
Keyword(s):  
Elevated Temperatures ◽  
Isothermal Oxidation ◽  
Tensile Behavior ◽  
Oxidation Behaviour ◽  
High Entropy Alloy ◽  
Dual Phase ◽  
High Entropy Alloys ◽  
High Entropy ◽  
Al2o3 Phase

In recent times, there has been a significant volume of work on Eutectic High Entropy Alloys (EHEAs) owing to their remarkable castability combined with excellent mechanical properties, which aids in clearing obstacles for their technological applications. One of the most common EHEAs, which has been of enormous interest at present, primarily owing to its solidification and tensile behavior, is AlCoCrFeNi2.1. However, to aim for high-temperature applications, oxidation behaviour of material is one of the major aspects that needs to be extensively investigated. To this end, the present work aims to study the phases evolved during oxidation at elevated temperatures as high as 950 and 1000°C in AlCoCrFeNi2.1 using XRD and also to determine the rate law followed for isothermal oxidation of this alloy at 950 and 1000°C, in order to understand the role of Al2O3 phase formed during isothermal oxidation at 950 and 1000°C.

scholarly journals Effect of Copper Addition on the AlCoCrFeNi High Entropy Alloys Properties via the Electroless Plating and Powder Metallurgy Technique

Crystals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 540
Author(s):  
Mohamed Ali Hassan ◽  
Hossam M. Yehia ◽  
Ahmed S. A. Mohamed ◽  
Ahmed Essa El-Nikhaily ◽  
Omayma A. Elkady
Keyword(s):  
Compressive Strength ◽  
Powder Metallurgy ◽  
Atomic Radius ◽  
The Other ◽  
High Entropy Alloy ◽  
Coating Process ◽  
High Entropy Alloys ◽  
Powder Metallurgy Technique ◽  
Copper Metal ◽  
High Entropy

To improve the AlCoCrFeNi high entropy alloys’ (HEAs’) toughness, it was coated with different amounts of Cu then fabricated by the powder metallurgy technique. Mechanical alloying of equiatomic AlCoCrFeNi HEAs for 25 h preceded the coating process. The established powder samples were sintered at different temperatures in a vacuum furnace. The HEAs samples sintered at 950˚C exhibit the highest relative density. The AlCoCrFeNi HEAs model sample was not successfully produced by the applied method due to the low melting point of aluminum. The Al element’s problem disappeared due to encapsulating it with a copper layer during the coating process. Because the atomic radius of the copper metal (0.1278 nm) is less than the atomic radius of the aluminum metal (0.1431 nm) and nearly equal to the rest of the other elements (Co, Cr, Fe, and Ni), the crystal size powder and fabricated samples decreased by increasing the content of the Cu wt%. On the other hand, the lattice strain increased. The microstructure revealed that the complete diffusion between the different elements to form high entropy alloy material was not achieved. A dramatic decrease in the produced samples’ hardness was observed where it decreased from 403 HV at 5 wt% Cu to 191 HV at 20 wt% Cu. On the contrary, the compressive strength increased from 400.034 MPa at 5 wt% Cu to 599.527 MPa at 15 wt% Cu with a 49.86% increment. This increment in the compressive strength may be due to precipitating the copper metal on the particles’ surface in the nano-size, reducing the dislocations’ motion, increasing the stiffness of produced materials. The formability and toughness of the fabricated materials improved by increasing the copper’s content. The thermal expansion has increased gradually by increasing the Cu wt%.

scholarly journals Refractory Metal (Nb) Intermetallic Composites, High Entropy Alloys, Complex Concentrated Alloys and the Alloy Design Methodology NICE—Mise-en-scène † Patterns of Thought and Progress

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 989
Author(s):  
Panos Tsakiropoulos
Keyword(s):  
Solid Solution ◽  
Refractory Metal ◽  
Design Methodology ◽  
Alloy Design ◽  
High Entropy Alloys ◽  
Laves Phases ◽  
High Entropy ◽  
High Temperature Materials ◽  
Mise En Scene ◽  
Intermetallic Composite

The paper reflects on the usefulness of the alloy design methodology NICE (Niobium Intermetallic Composite Elaboration) for the development of new Nb-containing metallic ultra-high-temperature materials (UHTMs), namely refractory metal (Nb) intermetallic composites (RM(Nb)ICs), refractory high entropy alloys (RHEAs) and refractory complex concentrated alloys (RCCAs), in which the same phases can be present, specifically bcc solid solution(s), M5Si3 silicide(s) and Laves phases. The reasons why a new alloy design methodology was sought and the foundations on which NICE was built are discussed. It is shown that the alloying behavior of RM(Nb)ICs, RHEAs and RCCAs can be described by the same parameters. The practicality of parameter maps inspired by NICE for describing/understanding the alloying behavior and properties of alloys and their phases is demonstrated. It is described how NICE helps the alloy developer to understand better the alloys s/he develops and what s/he can do and predict (calculate) with NICE. The paper expands on RM(Nb)ICs, RHEAs and RCCAs with B, Ge or Sn, the addition of which and the presence of A15 compounds is recommended in RHEAs and RCCAs to achieve a balance of properties.

Thermal stability and oxidation resistance of FeCrxCoNiB high-entropy alloys coatings by laser cladding

2019 ◽  
Vol 359 ◽  
pp. 132-140 ◽  
Author(s):  
Fa Chang ◽  
Bingjie Cai ◽  
Chong Zhang ◽  
Biao Huang ◽  
Shuai Li ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Oxidation Resistance ◽  
Laser Cladding ◽  
High Entropy Alloys ◽  
High Entropy

Microstructure stability and oxidation behaviour of (FeCoNiMo)90(Al/Cr)10 high-entropy alloys

2019 ◽  
Vol 35 (15) ◽  
pp. 1883-1890 ◽  
Author(s):  
C. Chen ◽  
N. Liu ◽  
J. Zhang ◽  
J. Cao ◽  
L. J. Wang ◽  
...  
Keyword(s):  
Oxidation Behaviour ◽  
High Entropy Alloys ◽  
High Entropy ◽  
Microstructure Stability

Isothermal Oxidation Behavior of a New Directionally Solidified Ni-Base Superalloy in Air at Different Temperature

2010 ◽  
Vol 654-656 ◽  
pp. 538-541
Author(s):  
Lei Wang ◽  
Yan Huang ◽  
Zhuo Zhao ◽  
Yang Liu ◽  
Jian Tao Wu ◽  
...  
Keyword(s):  
Oxidation Resistance ◽  
Oxidation Behavior ◽  
Isothermal Oxidation ◽  
Oxidation Behaviour ◽  
Diffusion Activation Energy ◽  
Directionally Solidified ◽  
Temperature Range ◽  
Parabolic Law ◽  
Diffusion Activation ◽  
Base Superalloy

The isothermal oxidation behaviour under static atmosphere of a new directionally solidified Ni-base superalloy was investigated. The results showed that the oxidation kinetics curves of the alloy follow parabolic law in the temperature range of 750-950°C. The diffusion activation energy Q is to be about 244.86 kJ•mol-1 and the oxidation within this temperature range is mainly controlled by Cr3+ diffusion among Cr2O3 oxidation film. The oxidation resistance grade of the alloy is perfect anti-oxidation within 750-850°C, and anti-oxidation within 900-950°C. The oxidation film can be divided into TiO2, Cr2O3+TiTaO4+NiCr2O4, Al2O3 and TiN layers, from the surface to inside. Priority oxidation and the inside oxidation of Al are considered with the oxidation of Ti and the depletion of Cr, and it is the key point for the improving of oxidation resistance.

Oxidation resistance properties of refractory high-entropy alloys with varied AlxCrTiMo content

2020 ◽  
Vol 56 (4) ◽  
pp. 3551-3561
Author(s):  
Ruiyang Zhang ◽  
Junhu Meng ◽  
Jiesheng Han ◽  
Kelimu Tulugan ◽  
Rui Zhang
Keyword(s):  
Oxidation Resistance ◽  
High Entropy Alloys ◽  
High Entropy

Oxidation Behaviour of Nickel-Based Alloys Containing High Re Contents Comparable to the Third Generation Nickel-Based Superalloys

2004 ◽  
Vol 449-452 ◽  
pp. 349-352 ◽  
Author(s):  
Yoshinori Murata ◽  
Masahiko Morinaga ◽  
Ryokichi Hashizume
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
High Temperature Oxidation ◽  
Oxidation Behaviour ◽  
The Other ◽  
Third Generation ◽  
Temperature Oxidation ◽  
Oxidation Test ◽  
Al Content ◽  
The Third

In order to elucidate the Re effect on oxidation resistance, a high-temperature oxidation test was conducted with two groups of Ni-based superalloys. One group of alloys was characterized by 10mol%Al content (10-Al series). The other group of alloys was characterized by 15mol%Al content (15-Al series). The oxidation resistance decreased clearly with increasing Re content in the 10-Al series alloys, but did not in the 15-Al series alloys.

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