1. |
- Wani, I. S., et al.
(författare)
-
Effect of severe cold-rolling and annealing on microstructure and mechanical properties of AlCoCrFeNi 2.1 eutectic high entropy alloy
- 2017
-
Ingår i: IOP Conference Series: Materials Science and Engineering. - 1757-8981 .- 1757-899X. ; 194:1
-
Konferensbidrag (refereegranskat)abstract
- The possibility of microstructural refinement and improvement of mechanical properties by severe cold-rolling was investigated in an AlCoCrFeNi2.1 lamellar eutectic high entropy alloy (EHEA). The as-cast alloy revealed fine scale eutectic mixture of L12 (ordered FCC) and B2 (ordered BCC) phases. During severe cold-rolling up to 90% reduction in thickness the B2 phase maintained the ordered structure, while the L12 phase showed the evolution of a nanocrystalline structure and progressive disordering. Annealing of the severely cold-rolled material resulted in the formation of duplex microstructures composed of two different phases with equiaxed morphologies and significant resistance to grain growth up to 1200°C. Annealing at 1000°C resulted in an optimum strength-ductility balance with the tensile strength of 1175 MPa and the total elongation of 23%. The present results showed that severe cold-rolling and annealing can impart very attractive mechanical properties in complex EHEAs.
|
|
2. |
- Calard, Francois, et al.
(författare)
-
Designing sterically demanding thiolate coated AuNPs for electrical characterization of BPDT in a NP-molecule-nanoelectrode platform
- 2017
-
Ingår i: Molecular Systems Design & Engineering. - : ROYAL SOC CHEMISTRY. - 2058-9689. ; 2:2, s. 133-139
-
Tidskriftsartikel (refereegranskat)abstract
- Molecular electronics with single or few molecules requires a stable metal-molecule nanojunction platform. Herein, we report the design and synthesis of gold nanoparticles coated with sterically demanding thiol ligands that are essential to fabricate a versatile and stable nanoelectrode-molecule-nanoparticle platform suitable for electrical characterization of small organic molecules. By combining.-tetraphenylmethane ether functionalized alkyl thioacetate and alkyl thiols, we prepared highly stable gold nanoparticles in a one-phase reaction providing simple and efficient purification. This robust preparation gives highly pure nanoparticles in very high yields (up to 90%) with long-time shelf stability. The synthesis in this work has superior reproducibility compared to previous synthesis processes that are currently being used for such molecular electronics platforms. Electron microscopy confirms the formation of uniform and small nanoparticles in the range of 5 to 7 nm. These nanoparticles with different ligand surface coverages were placed in a 20 nm nanoelectrode setup using dielectrophoretic forces. This setup was utilized to characterize the conductivity of the molecular wire 4,4'-biphenyldithiol introduced via ligand placeexchange under ambient conditions.
|
|
3. |
- Wani, I. S., et al.
(författare)
-
Cold-rolling and recrystallization textures of a nano-lamellar AlCoCrFeNi2.1 eutectic high entropy alloy
- 2017
-
Ingår i: Intermetallics. - : Elsevier BV. - 0966-9795. ; 84, s. 42-51
-
Tidskriftsartikel (refereegranskat)abstract
- The development of texture during cold-rolling and recrystallization was investigated in a AlCoCrFeNi2.1 eutectic high entropy alloy (EHEA). For this purpose, the as-cast alloy was cold-rolled to 90% reduction in thickness and annealed at temperatures ranging from 800 °C to 1200 °C. The microstructure of the as-cast EHEA showed a nano-lamellar mixture of L12 and B2 phases. The B2 phase was significantly harder than the L12 phase. Development of an ultrafine microstructure was observed after 90% cold-rolling. During cold-rolling, progressive disordering of the L12 phase was observed while the B2 phase maintained the ordered structure. The progressive disordering and development of a predominantly brass type texture in the L12 phase correlated well with profuse shear band formation during cold-rolling. The B2 phase showed the presence of the {111} component which was typical for cold-rolled B2 alloys. An ultrafine duplex structure of equiaxed L12 and B2 phases developed after complete recrystallization that showed significant resistance to grain growth up to very high annealing temperatures (?1300 °C). The remarkable resistance to grain growth compared to conventional or even other single or dual phase HEAs was due to the formation of a homogeneous duplex structure where growth of one phase was effectively retarded by the other phase. The strong presence of the ?-fiber components, but weak BR ({236} ) and D ({113} ) components in the recrystallization texture of the L12/FCC phase was due to the absence of strong preferential nucleation or growth. Presence of ND-fiber (ND// ) with strong {111} component in the recrystallization texture of the B2 phase indicated ease of nucleation from similarly oriented regions in the deformed microstructure.
|
|