| 1. |
- Bhattacharjee, T., et al.
(författare)
-
Effect of low temperature on tensile properties of AlCoCrFeNi2.1 eutectic high entropy alloy
- 2018
-
Ingår i: Materials Chemistry and Physics. - : Elsevier BV. - 0254-0584. ; 210, s. 207-212
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of low temperature on tensile properties of a AlCoCrFeNi 2.1 eutectic high entropy alloy (EHEA) was investigated in the present work. Transmission electron microscopy (TEM) showed that the initial as-cast microstructure consisted of B2 (ordered body centered cubic structure) and L1 2 (ordered face centered cubic structure) phases. Upon tensile testing at temperatures ranging from room temperature (RT) to −196 °C (77 K), the L1 2 phase became disordered, changing to a simple FCC (face centered cubic) crystal structure whereas the B2 phase maintained an ordered structure. An increase over 300 MPa was observed in the ultimate tensile strength (σ UTS ) of the −196 °C tensile tested sample compared to the room temperature tensile tested sample, while keeping almost similar amount of total elongation. TEM results indicated an increase in the dislocation activity in the FCC phase as well as B2 phase in the −196 °C tensile tested sample compared to the sample deformed at room temperature.
|
|
| 2. |
- Bhattacharjee, T., et al.
(författare)
-
Simultaneous Strength-Ductility Enhancement of a Nano-Lamellar AlCoCrFeNi2.1 Eutectic High Entropy Alloy by Cryo-Rolling and Annealing
- 2018
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 8:1
-
Tidskriftsartikel (refereegranskat)abstract
- Nano-lamellar (L1 2 + B2) AlCoCrFeNi 2.1 eutectic high entropy alloy (EHEA) was processed by cryo-rolling and annealing. The EHEA developed a novel hierarchical microstructure featured by fine lamellar regions consisting of FCC lamellae filled with ultrafine FCC grains (average size ∼200-250 nm) and B2 lamellae, and coarse non-lamellar regions consisting of ultrafine FCC (average size ∼200-250 nm), few coarse recrystallized FCC grains and rather coarse unrecrystallized B2 phase (∼2.5 μm). This complex and hierarchical microstructure originated from differences in strain-partitioning amongst the constituent phases, affecting the driving force for recrystallization. The hierarchical microstructure of the cryo-rolled and annealed material resulted in simultaneous enhancement in strength (Yield Strength/YS: 1437 ± 26 MPa, Ultimate Tensile Strength/UTS: 1562 ± 33 MPa) and ductility (elongation to failure/e f ∼ 14 ± 1%) as compared to the as-cast as well as cold-rolled and annealed materials. The present study for the first time demonstrated that cryo-deformation and annealing could be a novel microstructural design strategy for overcoming strength-ductility trade off in multiphase high entropy alloys.
|
|
| 3. |
- Patel, A., et al.
(författare)
-
Strain-path controlled microstructure, texture and hardness evolution in cryo-deformed AlCoCrFeNi2.1 eutectic high entropy alloy
- 2018
-
Ingår i: Intermetallics. - : Elsevier BV. - 0966-9795. ; 97, s. 12-21
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of strain path on microstructure, texture and hardness properties of AlCoCrFeNi 2.1 eutectic high entropy alloy containing ordered FCC (L1 2 ) and ordered BCC (B2) was investigated. The EHEA was cryo-rolled using UCR, MSCR (during which the samples were rotated by 90° around the ND between each pass) and TSCR(45°) (in which the samples were deformed by unidirectional rolling to half of the total strain and then diagonally rolled for rest half of the strain). The UCR processed material showed a rather heterogeneous microstructure. The textures of the L1 2 /FCC and B2 phases in the MSCR processed material agreed with the cross-rolling texture of the corresponding single phase materials, while the texture of the two phases in the TSCR(45°) processed materials appeared rather weak. Upon annealing at 800 °C, the UCR processed materials showed a novel heterogeneous microstructure, while the MSCR and TSCR(45°) processed materials revealed microduplex structure. The heterogeneous microstructure was replaced by the usual microduplex structure at higher annealing temperatures. The annealing texture of the L1 2 /FCC phase showed the presence of α-fiber (ND// < 011 > ) components while the B2 phase showed strong ND-fiber (ND// < 111 > ) components. The UCR processed material with novel heterogeneous microstructure showed much greater hardness as compared to the MSCR and TSCR(45°) processed materials. The present results indicate that strain path exerted significant influence in controlling microstructure, texture and hardness properties of EHEA.
|
|
