Difference between revisions of "Yaron Amouyal"

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I graduated from the Technion – Israel Institute of Technology (Ph.D.) and joined Prof. David [[Seidman_Group|Seidman group]] in August 2007 as a post-doctoral fellow. My current research activity is investigating the formation of defects during the solidification of [http://arc.nucapt.northwestern.edu/Ni-Based_Superalloys Ni-based superalloys] applied for turbine blades in aeronautical jet engines. Common defects occurring during the directional solidification of these single-crystalline blades are long chains of grains that are highly disoriented with respect to the matrix, and are referred to as “freckle chains”. Freckles may cause degradation in the alloy mechanical properties at high-temperatures, and therefore should be avoided. Besides this technological challenge, the persisting effort being made in the technology of jet engines is elevating their working temperature in order to improve their thermodynamic efficiency. The latter implies a demand for improving these alloys high-temperature creep and oxidation resistance. Both problems strongly depend on the alloy composition and morphology in the nanometer length scale.  
+
Common defects occurring during the directional solidification of these single-crystalline blades are long chains of grains that are highly disoriented with respect to the matrix, and are referred to as “freckle chains”. Freckles may cause degradation in the alloy mechanical properties at high-temperatures, and therefore should be avoided. Besides this technological challenge, the persisting effort being made in the technology of jet engines is elevating their working temperature in order to improve their thermodynamic efficiency. The latter implies a demand for improving these alloys high-temperature creep and oxidation resistance. Both problems strongly depend on the alloy composition and morphology in the nanometer length scale.  
 
For this purpose, we apply the latest version of the three-dimensional Atom Probe Tomography ([[3DAP|APT]]), namely the Local-Electrode Atom-Probe ([[LEAP]]). Our strategy is to produce an array of tips (microposts) from the region of a freckle (several millimeters in size), and to characterized each one of them individually by the LEAP. While a single tip has the lateral dimensions of several micrometers, the typical analysis volume obtained by the LEAP is tens of nm cube (~10M atoms). Additional characterization techniques, such as TEM, are being applied in order to span length scales. In this manner we hope to characterize the morphologies and chemistries of individual defect-rich zones at all pertinent length scales down to the sub-nanometer scale, which may help us understanding the role that each alloying element plays in the nucleation of freckles.
 
For this purpose, we apply the latest version of the three-dimensional Atom Probe Tomography ([[3DAP|APT]]), namely the Local-Electrode Atom-Probe ([[LEAP]]). Our strategy is to produce an array of tips (microposts) from the region of a freckle (several millimeters in size), and to characterized each one of them individually by the LEAP. While a single tip has the lateral dimensions of several micrometers, the typical analysis volume obtained by the LEAP is tens of nm cube (~10M atoms). Additional characterization techniques, such as TEM, are being applied in order to span length scales. In this manner we hope to characterize the morphologies and chemistries of individual defect-rich zones at all pertinent length scales down to the sub-nanometer scale, which may help us understanding the role that each alloying element plays in the nucleation of freckles.
 
This information will be used as input data for ab-initio Molecular Dynamics (AIMD) simulations of the thermodynamics of these alloys, and will enable us to formulate predictive models for the conditions where freckling can be avoided.
 
This information will be used as input data for ab-initio Molecular Dynamics (AIMD) simulations of the thermodynamics of these alloys, and will enable us to formulate predictive models for the conditions where freckling can be avoided.
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'''to investigate atomistic-level phenomena in nickel-based superalloys''''''
 
'''to investigate atomistic-level phenomena in nickel-based superalloys''''''
  
 +
I graduated from the Technion – Israel Institute of Technology (Ph.D.) and joined Prof. David [[Seidman_Group|Seidman group]] in August 2007 as a post-doctoral fellow. My current research activity is investigating the formation of defects during the solidification of [http://arc.nucapt.northwestern.edu/Ni-Based_Superalloys Ni-based superalloys] applied for turbine blades in aeronautical jet engines.
  
 
One of the most efficient energy conversion devices is the turbine engine, which is
 
One of the most efficient energy conversion devices is the turbine engine, which is
 
utilized for either aeronautical jet engines or natural-gas fired land-based electrical power
 
utilized for either aeronautical jet engines or natural-gas fired land-based electrical power
 
generators; a single unit can produce up to 500 Mega-Watt. Owing to their excellent hightemperature
 
generators; a single unit can produce up to 500 Mega-Watt. Owing to their excellent hightemperature
strength as well as creep and oxidation resistance, nickel-based superalloys are
+
strength as well as creep and oxidation resistance, nickel-based superalloys are the ideal materials for turbine blade applications. Ni-based alloys derive their properties from their unique microstructure comprising Ni3Al-gamma’(L12)- precipitates coherently dispersed in a Ni-based gamma(f.c.c.)- matrix. The continuing efforts made to increase the thermodynamic efficiency of the turbines, i.e., to obtain a high ratio of energy yield to fuel consumption,require high working temperatures (>1200 ºC). Elevating the service temperature of a turbine engine implies improving the high-temperature properties of these superalloys. In this context,there are several phenomena that are critical for high-temperature performance that were studied by us:
30
 
the ideal materials for turbine blade applications. Ni-based alloys derive their properties from
 
their unique microstructure comprising Ni3Al-g’(L12)- precipitates coherently dispersed in a
 
Ni-based g(f.c.c.)- matrix. The continuing efforts made to increase the thermodynamic
 
efficiency of the turbines, i.e., to obtain a high ratio of energy yield to fuel consumption,
 
require high working temperatures (>1200 ºC). Elevating the service temperature of a turbine
 
engine implies improving the high-temperature properties of these superalloys. In this context,
 
there are several phenomena that are critical for high-temperature performance that were
 
studied by us:
 
  
1) Segregation of refractory elements at the /�’ interfaces correlate with the interfacial free
+
1) Segregation of refractory elements at the gamma/gamma' interfaces correlate with the interfacial free energy, thus related to the precipitates temporal evolution at high temperatures, and affecting the alloys’ mechanical properties.
energy, thus related to the precipitates temporal evolution at high temperatures, and
 
affecting the alloys’ mechanical properties.
 
  
2) Partitioning behavior of refractory elements to the - and �’-phases determines the lattice
+
2) Partitioning behavior of refractory elements to the gamma- and gamma’-phases determines the lattice parameter mismatch at the coherent gamma/gamma'  interface, thus affecting the alloys’ mechanical properties at high temperatures.
parameter mismatch at the coherent /�’ interface, thus affecting the alloys’ mechanical
 
properties at high temperatures.
 
  
3) A major factor limiting the operating temperature is the formation of chains of misoriented
+
3) A major factor limiting the operating temperature is the formation of chains of misoriented grains, called “freckles”, on the surface of the single-crystal turbine blades during their solidification. Freckles introduce internal interfaces and serve as nucleation sites for micro-cracks as well as short-circuit diffusion paths, thereby reducing creep resistance. Their formation is associated with the solid/liquid partitioning of elements during
grains, called “freckles”, on the surface of the single-crystal turbine blades during their
+
solidifications, which affects the liquid local density. Eliminating the formation of freckles can be achieved by completely characterizing the alloy's crystallography, morphology, and composition at the micrometer to nanometer length scales.
solidification. Freckles introduce internal interfaces and serve as nucleation sites for
 
micro-cracks as well as short-circuit diffusion paths, thereby reducing creep resistance.
 
Their formation is associated with the solid/liquid partitioning of elements during
 
solidifications, which affects the liquid local density. Eliminating the formation of freckles
 
can be achieved by completely characterizing the alloy's crystallography, morphology, and
 
composition at the micrometer to nanometer length scales.
 

Revision as of 10:42, 30 January 2011

Yaron Amouyal
Research: Freckle formation in Ni-based superalloys
Education: Ph.D., Technion - Israel Institute of Technology
M.Sc., Technion, Israel
Publications: Publications by Amouyal in our database

Contact

Dr. Yaron Amouyal
Materials Science and Engineering
2220 North Campus Drive
Evanston, IL 60208
Phone: 847.467.5698
Email:
Fax: 847.467.2269

Common defects occurring during the directional solidification of these single-crystalline blades are long chains of grains that are highly disoriented with respect to the matrix, and are referred to as “freckle chains”. Freckles may cause degradation in the alloy mechanical properties at high-temperatures, and therefore should be avoided. Besides this technological challenge, the persisting effort being made in the technology of jet engines is elevating their working temperature in order to improve their thermodynamic efficiency. The latter implies a demand for improving these alloys high-temperature creep and oxidation resistance. Both problems strongly depend on the alloy composition and morphology in the nanometer length scale. For this purpose, we apply the latest version of the three-dimensional Atom Probe Tomography (APT), namely the Local-Electrode Atom-Probe (LEAP). Our strategy is to produce an array of tips (microposts) from the region of a freckle (several millimeters in size), and to characterized each one of them individually by the LEAP. While a single tip has the lateral dimensions of several micrometers, the typical analysis volume obtained by the LEAP is tens of nm cube (~10M atoms). Additional characterization techniques, such as TEM, are being applied in order to span length scales. In this manner we hope to characterize the morphologies and chemistries of individual defect-rich zones at all pertinent length scales down to the sub-nanometer scale, which may help us understanding the role that each alloying element plays in the nucleation of freckles. This information will be used as input data for ab-initio Molecular Dynamics (AIMD) simulations of the thermodynamics of these alloys, and will enable us to formulate predictive models for the conditions where freckling can be avoided.

Combination of Atom Probe Tomography (APT) and Density Functional Theory (DFT) to investigate atomistic-level phenomena in nickel-based superalloys'

I graduated from the Technion – Israel Institute of Technology (Ph.D.) and joined Prof. David Seidman group in August 2007 as a post-doctoral fellow. My current research activity is investigating the formation of defects during the solidification of Ni-based superalloys applied for turbine blades in aeronautical jet engines.

One of the most efficient energy conversion devices is the turbine engine, which is utilized for either aeronautical jet engines or natural-gas fired land-based electrical power generators; a single unit can produce up to 500 Mega-Watt. Owing to their excellent hightemperature strength as well as creep and oxidation resistance, nickel-based superalloys are the ideal materials for turbine blade applications. Ni-based alloys derive their properties from their unique microstructure comprising Ni3Al-gamma’(L12)- precipitates coherently dispersed in a Ni-based gamma(f.c.c.)- matrix. The continuing efforts made to increase the thermodynamic efficiency of the turbines, i.e., to obtain a high ratio of energy yield to fuel consumption,require high working temperatures (>1200 ºC). Elevating the service temperature of a turbine engine implies improving the high-temperature properties of these superalloys. In this context,there are several phenomena that are critical for high-temperature performance that were studied by us:

1) Segregation of refractory elements at the gamma/gamma' interfaces correlate with the interfacial free energy, thus related to the precipitates temporal evolution at high temperatures, and affecting the alloys’ mechanical properties.

2) Partitioning behavior of refractory elements to the gamma- and gamma’-phases determines the lattice parameter mismatch at the coherent gamma/gamma' interface, thus affecting the alloys’ mechanical properties at high temperatures.

3) A major factor limiting the operating temperature is the formation of chains of misoriented grains, called “freckles”, on the surface of the single-crystal turbine blades during their solidification. Freckles introduce internal interfaces and serve as nucleation sites for micro-cracks as well as short-circuit diffusion paths, thereby reducing creep resistance. Their formation is associated with the solid/liquid partitioning of elements during solidifications, which affects the liquid local density. Eliminating the formation of freckles can be achieved by completely characterizing the alloy's crystallography, morphology, and composition at the micrometer to nanometer length scales.