This document discusses recrystallization in metals and methods to investigate the nucleation stage of recrystallization. It summarizes different techniques to induce or inhibit recrystallization including deformation, annealing, and rapid/ultrafast heating methods. Instrumented indentation and electron backscatter diffraction are identified as tools to characterize local microstructure changes during the initial nucleation events. Future work should focus on controlling nucleation sites and integrating experimental data on local misorientation into recrystallization models.
Film Properties of ALD SiNx Deposited by Trisilylamine and N2 PlasmaBeneq
Presented by Dr. Markus Bosund
Silicon nitride is a widely used material in semiconductor applications‚ such as gate dielectrics‚ III/V surface passivation and etch stop layer.
PEALD SiNx films have been previously grown using aminosilanes like BTBAS with N2 plasma [1]. These processes generally have a relatively low growth rate of 0.15 - 0.21 Å/cycle and high film quality can only be reached at above 300 °C deposition temperatures. Trisilylamine (TSA) has been previously combined with N2/H2 plasma at 300–400 °C [2]‚ NH3 plasma at 50–400 °C [3] and N2 plasma at 250 – 350 °C [4] to grow PEALD SiNx films. However‚ in these works the low temperature range has remained either inaccessible or uncharted.
In this work we explored the PEALD TSA-N2 plasma process with a wide deposition temperature range from 50 to 350 °C. Focus was given to the electrical and optical properties of the films. A Beneq TFS 200 capacitively coupled hot wall plasma ALD reactor was used at direct plasma mode. It was found that reactor temperature‚ and plasma power and time had the highest impact on the film properties. Film deposition was observed at temperatures as low as 50 °C. Metal insulator semiconductor (MIS) structures were used to determine the breakdown field and leakage current at different temperatures. Films were dipped in 1 % HF solution for etch rate determination.
Influence of Doping and Annealing on Structural, Optical and Electrical prope...ijeei-iaes
The optical gap of the films was calculated from the curve of absorption coefficient (αhע)2 vs. hע and was found to be 3.8 eV at room temperature, and this value decreases from 3.8 to 3.58 eV with increasing of annealing temperature up to 473-673 K, and increases with the Ga doping. λ cutoff was calculated for ZnO and showed an increase with increasing annealing temperature and shifting to longer wavelength, while with doping the λcutoff shifted to shorter wavelength. The photoluminescence (PL) results indicate that the pure ZnO thin films grown at room temperature show strong peaks at 640 nm , but GaO doped ZnO films showed a band emission in the yellow-green spectral region (380 to 450nm).
Film Properties of ALD SiNx Deposited by Trisilylamine and N2 PlasmaBeneq
Presented by Dr. Markus Bosund
Silicon nitride is a widely used material in semiconductor applications‚ such as gate dielectrics‚ III/V surface passivation and etch stop layer.
PEALD SiNx films have been previously grown using aminosilanes like BTBAS with N2 plasma [1]. These processes generally have a relatively low growth rate of 0.15 - 0.21 Å/cycle and high film quality can only be reached at above 300 °C deposition temperatures. Trisilylamine (TSA) has been previously combined with N2/H2 plasma at 300–400 °C [2]‚ NH3 plasma at 50–400 °C [3] and N2 plasma at 250 – 350 °C [4] to grow PEALD SiNx films. However‚ in these works the low temperature range has remained either inaccessible or uncharted.
In this work we explored the PEALD TSA-N2 plasma process with a wide deposition temperature range from 50 to 350 °C. Focus was given to the electrical and optical properties of the films. A Beneq TFS 200 capacitively coupled hot wall plasma ALD reactor was used at direct plasma mode. It was found that reactor temperature‚ and plasma power and time had the highest impact on the film properties. Film deposition was observed at temperatures as low as 50 °C. Metal insulator semiconductor (MIS) structures were used to determine the breakdown field and leakage current at different temperatures. Films were dipped in 1 % HF solution for etch rate determination.
Influence of Doping and Annealing on Structural, Optical and Electrical prope...ijeei-iaes
The optical gap of the films was calculated from the curve of absorption coefficient (αhע)2 vs. hע and was found to be 3.8 eV at room temperature, and this value decreases from 3.8 to 3.58 eV with increasing of annealing temperature up to 473-673 K, and increases with the Ga doping. λ cutoff was calculated for ZnO and showed an increase with increasing annealing temperature and shifting to longer wavelength, while with doping the λcutoff shifted to shorter wavelength. The photoluminescence (PL) results indicate that the pure ZnO thin films grown at room temperature show strong peaks at 640 nm , but GaO doped ZnO films showed a band emission in the yellow-green spectral region (380 to 450nm).
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Study on hardening mechanisms in aluminium alloysIJERA Editor
The Al-Zn-Mg alloys are most commonly used age-hardenable aluminium alloys. The hardening mechanism is
further enhanced in addition of Sc. Sc additions to aluminium alloys are more promising. Due to the
heterogeneous distribution of nano-sized Al3Sc precipitates hardening effect can be accelerated. Mainly,
highlight on hardening mechanism in Al-Zn-Mg alloys with Sc effect is to study. In addition, several
characterisations have been done to age-hardening measurements at elevated temperatures from 120oC to 180
oC. The ageing kinetics has also been calculated from Arrhenius equation. Furthermore, friction stir processing
(FSP) can be introduced to surface modification process and hardened the cast aluminium alloys. In this study,
hardening mechanism can be evaluated by Vicker’s hardness measurement and mechanical testing is present
task.
Study on hardening mechanisms in aluminium alloysIJERA Editor
The Al-Zn-Mg alloys are most commonly used age-hardenable aluminium alloys. The hardening mechanism is
further enhanced in addition of Sc. Sc additions to aluminium alloys are more promising. Due to the
heterogeneous distribution of nano-sized Al3Sc precipitates hardening effect can be accelerated. Mainly,
highlight on hardening mechanism in Al-Zn-Mg alloys with Sc effect is to study. In addition, several
characterisations have been done to age-hardening measurements at elevated temperatures from 120oC to 180
oC. The ageing kinetics has also been calculated from Arrhenius equation. Furthermore, friction stir processing
(FSP) can be introduced to surface modification process and hardened the cast aluminium alloys. In this study,
hardening mechanism can be evaluated by Vicker’s hardness measurement and mechanical testing is present
task.
Presentation of my first year result during my PhD thesis. The congress held at Athenes the last May 2009. These slides deal with the study of the forced wetting during the fall and spreading of a single zinc drop onto a steel surface after annealing according to the galvanizing process.
Shenpaz Focus -4010 (Dental Ceramic Furnace)
Enjoy beautiful restoration results while staying within budget with Shenpaz small footprint porcelain firing furnaces.
Ideal for new laboratories with limited space or established facilities looking for a cost-effective solution to high quality firing. Get more info :- http://agkem.in/product/shenpaz-focus-4010-dental-ceramic-furnace/
Study on hardening mechanisms in aluminium alloysIJERA Editor
The Al-Zn-Mg alloys are most commonly used age-hardenable aluminium alloys. The hardening mechanism is
further enhanced in addition of Sc. Sc additions to aluminium alloys are more promising. Due to the
heterogeneous distribution of nano-sized Al3Sc precipitates hardening effect can be accelerated. Mainly,
highlight on hardening mechanism in Al-Zn-Mg alloys with Sc effect is to study. In addition, several
characterisations have been done to age-hardening measurements at elevated temperatures from 120oC to 180
oC. The ageing kinetics has also been calculated from Arrhenius equation. Furthermore, friction stir processing
(FSP) can be introduced to surface modification process and hardened the cast aluminium alloys. In this study,
hardening mechanism can be evaluated by Vicker’s hardness measurement and mechanical testing is present
task.
Study on hardening mechanisms in aluminium alloysIJERA Editor
The Al-Zn-Mg alloys are most commonly used age-hardenable aluminium alloys. The hardening mechanism is
further enhanced in addition of Sc. Sc additions to aluminium alloys are more promising. Due to the
heterogeneous distribution of nano-sized Al3Sc precipitates hardening effect can be accelerated. Mainly,
highlight on hardening mechanism in Al-Zn-Mg alloys with Sc effect is to study. In addition, several
characterisations have been done to age-hardening measurements at elevated temperatures from 120oC to 180
oC. The ageing kinetics has also been calculated from Arrhenius equation. Furthermore, friction stir processing
(FSP) can be introduced to surface modification process and hardened the cast aluminium alloys. In this study,
hardening mechanism can be evaluated by Vicker’s hardness measurement and mechanical testing is present
task.
Presentation of my first year result during my PhD thesis. The congress held at Athenes the last May 2009. These slides deal with the study of the forced wetting during the fall and spreading of a single zinc drop onto a steel surface after annealing according to the galvanizing process.
Annealing and Microstructural Characterization of Tin-Oxide Based Thick Film ...Anis Rahman
Abstract. The sheet resistance of tin oxide based thick-film resistors exhibits two regions of temperature dependence,
described by hopping (23°C-200°C) and diffusion mechanisms (200°C-350°C), respectively.
Annealing these samples causes the sheet resistance to increase in both regions. In the post-annealed samples,
the hopping conduction range is extended by 50°C (23°C-250°C) while the hopping parameter, To, is decreased by
more than 50%. The activation energy of diffusion (0.60 eV) is the same for both pre- and post annealed samples, but
the magnitude of resistance in the diffusion controlled region is increased significantly as a result of annealing. These
changes are explained in terms of a net decrease in the concentration of tin ions in the glass matrix. From a careful
microstructural study it was found that a conduction path composed of tin-oxide grains or their clusters in contact
with each other does not exist in the present system. HREM micrographs showed the presence of nanocrystalline
tin-oxide particles in the glass phase separating the tin-oxide grain clusters. Estimated average separation between
the nanocrystals in 4 nm, consistent with a variable-range hopping conduction via the dissolved tin ions in the glass
matrix.
Palestra plenária do XII Encontro da SBPMat (Campos do Jordão, setembro/outubro de 2013). Palestrante: Mercouri G Kanatzidis - Northwestern University e Argonne National Laboratory (EUA).
Dislocations & Materials Classes , and strenthning mechanismsonadiaKhan
In brittle materials, failure in the film occurs when the stress exceeds a critical stress defined by the intrinsic atomic strength of the material and the nature of any critical defects. If the strength of the material can be increased or the size (or sharpness) of the defects decreased, then the film will be able to withstand higher levels of stress. It is important to emphasize that this approach will not reduce the stress in the system; so, bending and other detrimental effects will still occur.
The strength of the material can be increased by adding second-phase reinforcements that can be either permanent (e.g. fibers) or temporary (long-chain polymers). The size of critical defects can be modified through appropriate processing (either selection of route or control of processing) to ensure that the samples are free of critical defects. Large pores, introduced due to contamination, and poor powder packing or large grains are common strength-limiting defects in powder-based thick films – the use of fine grains and ensuring well-homogenized powders with no contaminants are therefore critical, as is high-quality deposition processing (Chapter 3).
Such strengthening mechanisms can play an important role, as there is a significant change in the mechanical properties of thick films during processing due to the rapidly evolving microstructure and chemistry of the system. Often, stresses in the system will increase before the strength of the material increases, leading to situations where the film is at a higher risk of failing mid-way through processing.
Overcoming Challenges of Integration
Reduce temperature
Reducing the temperature used for processing is by far the most effective way to overcome the challenges. It alleviates all the thermally induced issues, reduces (or even eliminates) chemical reactions, and reduces differential strains caused by reactions and temperature.
Separate reactants
Two reactive materials can be separated either by removing one material completely or by placing a barrier between the two materials. Protective atmospheres and barrier layers are frequently used.
Reduce differential strains
Select materials with comparable thermal expansions, those that do not undergo volume changes due to reactions or phase changes, or reduce the need to consolidate materials during processing.
Reduce film thickness
Building up multiple thin layers can allow much thicker films to be created, as each single layer is better able to withstand relative shrinkage during processing.
Strengthening
Modifying the materials to increase strength or interface strength of system can be used to prevent mechanical failure.
Read more
Creep of Intermetallics
M.-T. Perez-Prado, M.E. Kassner, in Fundamentals of Creep in Metals and Alloys (Third Edition), 2015
4.2.3 Strengthening Mechanisms
Several strengthening mechanisms have been utilized in order to improve the creep strength of NiAl alloys. Solid solution of Fe, Nb, Ta, Ti, and Zr produced only
Research Inventy : International Journal of Engineering and Science is published by the group of young academic and industrial researchers with 12 Issues per year. It is an online as well as print version open access journal that provides rapid publication (monthly) of articles in all areas of the subject such as: civil, mechanical, chemical, electronic and computer engineering as well as production and information technology. The Journal welcomes the submission of manuscripts that meet the general criteria of significance and scientific excellence. Papers will be published by rapid process within 20 days after acceptance and peer review process takes only 7 days. All articles published in Research Inventy will be peer-reviewed.
Effect of sintering time on the particle size and dielectric properties of La...ijceronline
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Magnetic nde characterization of tempered 2.25 cr 1mo steelAPOORVKRISHNA1
A descriptive presentation on heat treatment analysis of Tempered 2.25Cr-1Mo steel ,commonly known as P22 steel. The presentation includes history of the material, objective and work-plan with procedures adopted to carry out the project.
1. 1
RECRYSTALLIZATION IN METALS
FLORENT LEFEVRE-SCHLICK and DAVID EMBURY
Department of Materials Science and Engineering
McMaster University, Hamilton, ON, Canada
2. 2
OUTLINE
Recrystallization
What is it?
How is it usually treated?
Importance of local misorientation/strain gradients on “nucleation”
First stages of recrystallization; how can we investigate the “nucleation”?
Rapid heat treatments
What are they?
What can we expect from them?
Recrystallization in metals
Modeling
Conclusions-Future work
3. 3
What is it?
Fe
E =Estored=~100J/mol
Deformation
Heat
Recovery
(rearrangement of dislocations in sub grains)
Recrystallization
(development of new strain free grains)
Recrystallization
4. 4
Recrystallization
HOW DOES RECRYSTALLIZATION START?
“nucleation”
Strain Induced
Boundary Migration
∆Θ1
∆Θ2
∆Θ3
∆Θ4
∆Θ1
∆Θ3
∆Θ4
Θ1
Θ2
Θ1
Θ2
Θ2
E 1 E 2>
Coalescence and growth of subgrains
Migration of a boundary
In simple systems: small number of “nuclei” lead to recrystallized grains
5. 5
Improving the mechanical properties of materials
How does recrystallization proceed?
How to control recrystallization?
How to achieve an important grain refinement?
Can we control more than just the scale?
0
1000
2000
3000
4000
5000
6000
7000
0 2 4 6 8 10
d
-1/2
(µm
-1/2
)
σY(MPa)
Cu
Fe
Al
Recrystallization
Grain refinement strengthening
6. 6
Johnson, Mehl, Avrami, Kolmogorov approach
1 exp( )n
X Bt= − −
0
1
recrystallizedfractionX
time
Random distribution of nucleation sites
Constant rate of nucleation and growth n=4
Site saturation n=3
Recrystallization
7. 7
Johnson, Mehl, Avrami, Kolmogorov approach
Recrystallization
Is n misleading?
<1Fe-Mn-C
1.7Aluminium+ small amount of copper, 40% cold
rolled
4Fined grained Aluminium, low strain
4/3/2Constant nucleation rate 3d/2d/1d
3/2/1Site saturation 3d/2d/1d
9. 9
Particle Stimulated Nucleation
Leslie et al. (1963) Humphreys et al. (1977)
Oxide inclusions in Fe Al-Si system Cluster of SiO2 in Ni
Recrystallization originates at pre-existing subgrains within the deformation zone
Nucleation is affected by particle size and particle distribution
“NUCLEATION” OF RECRYSTALLIZATION
Recrystallization
10. 10
INVESTIGATING THE “NUCLEATION” EVENT
Injecting nucleation sites to increase N:
• Local misorientation (twins)
• Local strain gradient (high deformation)
Recrystallization
o
Impeding growth of recrystallized grains
• Rapid heat treatments
11. 11
What are rapid heat treatments?
T
time
•“Slow” heat treatment
(salt bath)
•“Rapid” heat treatment
(spot welding machine)
•“Ultra-fast” heat treatment
(pulsed laser)
T
time
T
time
seconds
mseconds
nano/pico/femtoseconds
Rapid heat treatments
12. 12
“Slow” heat treatment: Salt bath
Time/Temperature profile during salt bath
heat treatment
0
100
200
300
400
500
600
700
0 5 10 15
Time (sec)
Temperature(C)
Duration of the heat
treatment: 5 seconds.
Temperature range: 500o
C
to 650o
C.
Heating rate ~300C/sec
Cooling rate ~1000C/sec
Salt bath
13. 13
“NUCLEATION” IN IRON
Fe deformed by impact at 77K
50 µm B=[011]
01-1 -21-1
-200
21-1
-2-11
2-22
(-2-11)
(1-11)
grain
twin
Twinning plane {112}
Shear direction 111
Production of deformation twins to promote a variety of potential
nucleation sites for recrystallization, either at twin/grain
boundary or twin/twin intersections
4 µm
Salt bath
15. 15
“NUCLEATION” IN COPPER
50 µm
1 µm 4 µm
25 µm
Cu 60% cold rolled Cu ~ 2% recrystallized
5 seconds at 250o
C
No noticeable effect of annealing twins on nucleation
Salt bath
16. 16
45% cold rolled @ 77K
100µm
Stainless steel 316L
Cooperation with X. Wang
Salt bath
“NUCLEATION” IN STAINLESS STEEL
17. 17
2 min @ 950C
25µm
Stainless steel 316L
Average grain size: 7µm
Salt bath
“NUCLEATION” IN STAINLESS STEEL
18. 18
25µm
2 min @ 900C
Stainless steel 316L
Average grain size: 5µm
Salt bath
“NUCLEATION” IN STAINLESS STEEL
20. 20
1 min @ 800C
10µm
Role of annealing, deformation twins and phases on nucleation and growth?
Stainless steel 316L
Salt bath
“NUCLEATION” IN STAINLESS STEEL
21. 21
DF image (austenite)
DF image
(austenite + martensite)
DF image (Twin)
BF image
Salt bath
1 min @ 800C
Stainless steel 316L
Fine and complex deformed microstructure
Over a range of possible growing grains, only a few seem to grow
“NUCLEATION” IN STAINLESS STEEL
22. 22
Salt bath
Stainless steel 316L, 2 min @ 850C
25µm
RECRYSTALLIZATION AS A WAY TO CONTROL THE NATURE
OF GRAIN BOUNDARIES?
10o
20o
30o
40o
50o
60o
0%
30%
~30% of Σ3 boundaries
(rotation 60o
, axis <111>)
23. 23
“RAPID” HEAT TREATMENT: SPOT WELDING MACHINE
3mm
250 µm
Fe annealed (thickness = 500 µm)
Fe 60% cold rolled (thickness = 200 µm)
Electrode of Cu
Pulse discharge width: 1 msec
Energy output: 100 J to 1 J
Estimated heating rate ~105
K/sec
Spot welding machine
24. 24
PHASE TRANSITION IN IRON
50 µm 50 µm
40 J 20 J
Melted zone
Heated zone
Refinement of the microstructure via phase transitions
Distribution in grain size from 40 µm down to less than 1 µm
Spot welding machine
25. 25
RECRYSTALLIZATION AND PHASE TRANSITION IN IRON
40 J
50 µm100 µm
Refinement of the microstructure via phase transitions and recrystallization
Distribution in grain size from 100 µm down to less than 1 µm
Spot welding machine
Fe 60% cold rolled
26. 26
20 J
50 µm
Localized event along specific grain boundaries
Spot welding machine
RECRYSTALLIZATION AND PHASE TRANSITION IN IRON
Fe 60% cold rolled
27. 27
Laser pulse:
Energy (nJ to µJ)
Time (fsec to nsec)
Beam size (µm to mm)
Small volume on the surface
Rapid heating and cooling
(104
to 1012
K/sec)
Increase in pressure (up to TPa)
Shock wave.
“ULTRA FAST” HEAT TREATMENT: PULSE LASER IRRADIATION
(nano/pico/femtosecond)
Cooperation with Preston/Haugen group
~100 nm
to mm
Pulse lasers
28. 28
λ = 800 nm
The beam has a Gaussian profile
with a radius ω0
E0: full energy pulse (~10 µJ)
τp: duration of the pulse (~ 10 nsec/ 100psec/ 150 fsec)
φ: fluence or energy per unit area (J/cm2
)
φth: threshold fluence (J/cm2
)
fluence required to transform the surface
Pulse lasers
“ULTRA FAST” HEAT TREATMENT: PULSE LASER IRRADIATION
(nano/pico/femtosecond)
30. 30
SINGLE PULSE ABLATION OF FE
E = 9.2 µJ
10 µm
5 µm
E = 1.0 µJ
10 µm
E = 3.2 µJ
5 µm
E = 0.2 µJ
What is the temperature profile?
How to characterise the irradiated volume?
Pulse lasers
31. 31
Si substrate
SiO2 isolant layer
Platinum
2 mm
2 mm 100 µm
25 nm2 µm
resistor
connector
TEMPERATURE MEASUREMENT DEVICE
Summer work of B. Iqbar
Measuring the changes in resistivity of Pt estimating the temperature
Pulse lasers
32. 32
Fe annealed, 1 grain
Corrected harmonic contact stiffness: 1.106
N/m
0
10
20
30
200 400 600 800 1000 1200
Load On Sample (mN)
Displacement Into Surface (nm)
1
2
3
4
5
[6]
U
HD
I
E
M HN
L
0
100
200
300
400
200 400 600 800 1000 1200
Reduced Modulus (GPa)
Displacement Into Surface (nm)
IM
H
N
0
2
4
6
8
10
12
14
16
0 200 400 600 800 1000
Hardness (GPa)
Displacement Into Surface (nm)
1
2
3
4
5
[6]
I
M
HN
INSTRUMENTED INDENTATION
Pulse lasers
0
10
20
30
40
200 400 600 800 1000 1200
Load On Sample (mN)
Displacement Into Surface (nm)
[2]
3
4
U
HD
I
E
M HN
L
Fe annealed, 3 different grains
0
100
200
300
400
200 400 600 800 1000 1200
Reduced Modulus (GPa)
Displacement Into Surface (nm)
I
MH
N
0
2
4
6
8
10
12
14
16
200 400 600 800 1000 1200
Hardness (GPa)
Displacement Into Surface (nm)
[2]
3
4
IM HN
33. 33
1 2 3
12 11 10
-1
0
1
2
3
4
5
6
7
100 200 300 400
Load On Sample (mN)
Displacement Into Surface (nm)
1
2
3
4
5
6
7
8
[9]
10
11
12S
U
HDI EM
H
N
L
-2
0
2
4
6
8
10
12
14
16
18
20
100 200 300 400
Hardness (GPa)
Displacement Into Surface (nm)
1
2
3
4
5
6
7
8
[9]
10
11
12
IM HN
INSTRUMENTED INDENTATION
Pulse lasers
Softening of the deformed material?
Is there local melting/solidification or local heating?
34. 34
SGGrain I
Grain II
nucleus
Grain I
Grain II
)(
2
)(
tr
tG
γ
>
Modeling
ZUROB’S MODEL FOR RECRYSTALLIZATION
Needs input on local misorientations
35. 35
CONCLUSIONS – FUTURE WORK
Investigation of the first stage of recrystallization by:
o Designing microstructures to promote N
o Using rapid heat treatments to allow nucleation but not G
o
o
Characterize the heat treatment in terms of time/temperature
profile
Characterize the “nucleation” event in terms of local
misorientation, local strain gradient (EBSD)
Introduce the data on misorientation into Zurob’s model