scholarly journals Structure and high temperature mechanical properties of novel non-equiatomic Fe-(Co, Mn)-Cr-Ni-Al-(Ti) high entropy alloys

2018 ◽  
Vol 102 ◽  
pp. 140-151 ◽  
Author(s):  
N.D. Stepanov ◽  
D.G. Shaysultanov ◽  
M.A. Tikhonovsky ◽  
S.V. Zherebtsov
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
High Entropy Alloys ◽  
High Entropy ◽  
High Temperature Mechanical Properties

scholarly journals Microstructure and Mechanical Properties of the Ductile Al–Ti–Mo–Nb–V Refractory High Entropy Alloys

2021 ◽  
Author(s):  
Grzegorz Cieślak ◽  
Juliusz Dąbrowa ◽  
Monika Jawańska ◽  
Agnieszka Parzuchowska ◽  
Dariusz Oleszak
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Low Temperature ◽  
High Temperature Corrosion ◽  
High Entropy Alloys ◽  
High Entropy ◽  
Al Content ◽  
Microstructure And Mechanical Properties ◽  
Measured Stress ◽  
Vital Component

AbstractA number of non-equimolar refractory high entropy alloys (RF HEAs) from the Al–Ti–Mo–Nb–V system are synthesized, with the selected compositions aimed to balance the conflicting requirements of the low-temperature ductility and high-temperature corrosion protection. Based on the thermodynamic modeling and experimental results, all the obtained alloys are characterized by the single-phase B2 structure with V acting as the main phase stabilizer. The microstructure and mechanical properties appear to be controlled mainly by the Al content, which is especially visible on the example of hardness, with a maximum value of 545 HV for Al20Ti5Mo25Nb25V25 composition. For the selected Al20Ti5Mo25Nb25V25 and Al10Ti30Mo20Nb20V20 alloys, the measured stress–strain curves indicate the highly coveted, ductile room temperature behavior, with the values of ultimate strain measured under compression mode being 9.17 and 9.00 pct, respectively, and compressive fracture strain of 13.38 and 13.25 pct, respectively. The obtained results suggest that it is possible to include Al as a vital component of refractory HEAs without compromising their low-temperature ductility. The next intended step will be the characterization of the high-temperature corrosion behavior in order to investigate the potential selective oxidation capabilities of such materials.

scholarly journals Microstructure and Mechanical Properties of Wire Arc Additively Manufactured MoNbTaWTi High Entropy Alloys

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4512
Author(s):  
Jian Liu ◽  
Jing Li ◽  
Xian Du ◽  
Yonggang Tong ◽  
Rui Wang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
High Temperature ◽  
Additive Manufacturing ◽  
Inconel 718 ◽  
Solid Solution Phase ◽  
High Entropy Alloys ◽  
Inconel 718 Alloy ◽  
High Entropy ◽  
Wire Arc Additive Manufacturing

High-temperature resistant high-entropy alloys (HEAs) have attracted extensive attention due to their excellent thermodynamic stability and mechanical properties, especially at high temperatures. However, a highly effective method for large-size HEAs is still desirable but challengeable. This research reported a facile yet effective strategy for MoNbTaWTi HEAs via in-situ wire arc additive manufacturing (WAAM). The wire was MoNbTaWTi cable-type welding wire (CTWW) consisting of one center wire and seven twisted peripheral wires. Then, additive manufacturing of MoNbTaWTi high entropy alloys (HEAs) was accomplished, and various analytical techniques studied the microstructures and mechanical properties of the overlaying formed layers. X-ray diffraction showed the overlaying formed layers to contain a single disordered BCC solid solution phase with high-temperature structural stability. In addition, the single-phase BCC structure was maintained from 0 to 1400 °C. The bottom of the overlaying formed layers was made of columnar cellular structure, and the upper part resembled “cauliflower-like” fine dendrite and equiaxed crystal structure. The hardness of the overlaying formed layers averaged 533 HV0.2 at room temperature. At 1000 °C, the hardness was around 110 HV1, close to the value of Inconel 718 alloy (125 HV1). The compressive strength of the overlaying formed alloy layers displayed no sensitivity towards change in temperature from 500 to 1000 °C. As the temperature rose from 500 to 1000 °C, the compressive strength changed from 629 to 602 MPa, equivalent to only a 27 MPa decrease. The latter was much higher than the strength of Inconel 718 alloy at the same temperature (200 MPa).

TEM Studies of Grain Boundary Films in Si3N4 Ceramics

1991 ◽  
Vol 49 ◽  
pp. 930-931
Author(s):  
H.-J. Kleebe ◽  
J.S. Vetrano ◽  
J. Bruley ◽  
M. Rühle
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Silicon Nitride ◽  
Hot Isostatic Pressing ◽  
Amorphous Film ◽  
Liquid Phase Sintering ◽  
Second Phase ◽  
High Temperature Mechanical Properties ◽  
Triple Points ◽  
Boundary Films

It is expected that silicon nitride based ceramics will be used as high-temperature structural components. Though much progress has been made in both processing techniques and microstructural control, the mechanical properties required have not yet been achieved. It is thought that the high-temperature mechanical properties of Si3N4 are limited largely by the secondary glassy phases present at triple points. These are due to various oxide additives used to promote liquid-phase sintering. Therefore, many attempts have been performed to crystallize these second phase glassy pockets in order to improve high temperature properties. In addition to the glassy or crystallized second phases at triple points a thin amorphous film exists at two-grain junctions. This thin film is found even in silicon nitride formed by hot isostatic pressing (HIPing) without additives. It has been proposed by Clarke that an amorphous film can exist at two-grain junctions with an equilibrium thickness.

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