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1.*INTRODUCTION* 2.*EXPERIMENTAL*APPROACH* 3.*BIODUR*108* 4.*TI*GRADE*2*
23'
Biodur108*CORROSION*RESISTANCE*
5.*TI*GRADE*5* 6.*OTHERS* 7.*CONCLUSIONS*
100μm' 100μm'100μm'
Recuit_2
5mm800°C_1h_1
5mm800°C_2h
5mm
a)* c)*b)*
Figure*8:*Presence*of*nitrides*in*Biodur108*a)*in*the*annealed*state,**afer*a*heat4treatment*at*800°C*during*b)*1h*and*c)*2h*and*the*corresponding*resistance*to*piung*corrosion.**
Investigation on thermomechanical properties of high nitrogen nickel-free austenitic stainless steels,
commercially pure titanium and Ti - 6Al - 4V.Maïté BLANK, Andreas BLATTER1, Randoald MULLER1 and Ludger WEBER2
[email protected] Group, 2300 La Chaux-de-Fonds and 2Laboratory of Mechanical Metallurgy, EPFL, 1015 Lausanne, Switzerland
1. Goal of the project
2. experimental methodTENSILE TESTS
Determination of the appropriate warm rolling temperatureWARM ROLLING TESTSEvaluation of process efficiency
5. ti Grade 5Challenge: At room temperature, Ti Grade 5 (or Ti - 6Al - 4V) possesses a high yield strength (> 900MPa) and limited ductility (A ~ 45%). Both roll mills power and surface defects are thus limiting factors.
TEnsilE ProPErTiEs Vs. TEMPErATUrEHigh yield strength and low ductility even at 400°C
WARM ROLLED WIRESWarm rolling temperature: 400°C
Failure occured over the whole specimen length.
Possible mechanism involved: tensile stresses due to material spreading create voids that pro-pagate along shear bands, thus causing failure 3.
Possible alternative: warm rol-ling with lateral constraints.
7. conclusion
4. ti Grade 2Challenge: Ti Grade 2 (or commercially pure titanium) has limited ductility at room temperature (A ~ 60%). During cold rolling, edge cracks thus tend to appear at relatively low deformations.
WARM ROLLED WIRES PossiBlE MECHAnisMs inVolVED
3. Biodur108Challenge: Biodur108 is a high nitrogen nickel-free stainless steel containing about 1.1wt%n. Consequently, it has a high yield strength at room temperature (~ 700MPa) and a high strain hardening rate. Cold deformation of Biodur108 tends to be difficult due to the limited power of the roll mills.
YiElD sTrEnGTH Vs. TEMPErATUrEP proportional to σy
PoWEr rEQUirED Vs. PAssno more power gain over 200°C.
WARM ROLLED WIRESWarm rolling temperature: 200°C
Path performed: 10 - 7 - 5 - 3mm (no intermediary annealing)
Maximum crack size (thickness 3mm): 17μm
→ enables overcoming problems encountered during cold rolling.
6. Warm-rollinG related issuesinFlUEnCE oF niTriDEs on BioDUr108 Corrosion
rEsisTAnCE1.*INTRODUCTION* 2.*EXPERIMENTAL*APPROACH* 3.*BIODUR*108* 4.*TI*GRADE*2*
23'
Biodur108*CORROSION*RESISTANCE*
5.*TI*GRADE*5* 6.*OTHERS* 7.*CONCLUSIONS*
100μm' 100μm'100μm'
Recuit_2
5mm800°C_1h_1
5mm800°C_2h
5mm
a)* c)*b)*
Figure*8:*Presence*of*nitrides*in*Biodur108*a)*in*the*annealed*state,**afer*a*heat4treatment*at*800°C*during*b)*1h*and*c)*2h*and*the*corresponding*resistance*to*piung*corrosion.**
1.*INTRODUCTION* 2.*EXPERIMENTAL*APPROACH* 3.*BIODUR*108* 4.*TI*GRADE*2*
23'
Biodur108*CORROSION*RESISTANCE*
5.*TI*GRADE*5* 6.*OTHERS* 7.*CONCLUSIONS*
100μm' 100μm'100μm'
Recuit_2
5mm800°C_1h_1
5mm800°C_2h
5mm
a)* c)*b)*
Figure*8:*Presence*of*nitrides*in*Biodur108*a)*in*the*annealed*state,**afer*a*heat4treatment*at*800°C*during*b)*1h*and*c)*2h*and*the*corresponding*resistance*to*piung*corrosion.**
!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!P! ∝ !σ!!!!!!!!!
0!
20!
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0! 100! 200! 300! 400!
Area!re
duction![%
]!
Temperature![°C]!
Ti!Grade!5!
PM!(316L)!
ΔA&~20%&
Rolling!temperature!:!400°C!
Rolling!temperature!:!200°C!
!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!
!!
0!
5!
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0! 10! 20! 30! 40! 50! 60!
Crack&size&[μm]&
Area&reduction&[%]&
Maximum!crack!size!
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0! 100! 200! 300! 400!Yield!Strength![M
Pa]!
Temperature![°C]!
Ti!Grade!5!
PM!(316L)!
Δσy&~500&MPa&
626&MPa&!&
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Shear&bands&
Tensile!reduction!in!area!ln!(A0/A)!
Cracking!reduction!ln(t0/t)!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Shear&bands&
Tensile!reduction!in!area!ln!(A0/A)!
Cracking!reduction!ln(t0/t)!
1.*INTRODUCTION* 2.*EXPERIMENTAL*APPROACH* 3.*BIODUR*108* 4.*TI*GRADE*2*
23'
Biodur108*CORROSION*RESISTANCE*
5.*TI*GRADE*5* 6.*OTHERS* 7.*CONCLUSIONS*
100μm' 100μm'100μm'
Recuit_2
5mm800°C_1h_1
5mm800°C_2h
5mm
a)* c)*b)*
Figure*8:*Presence*of*nitrides*in*Biodur108*a)*in*the*annealed*state,**afer*a*heat4treatment*at*800°C*during*b)*1h*and*c)*2h*and*the*corresponding*resistance*to*piung*corrosion.**
1.*INTRODUCTION* 2.*EXPERIMENTAL*APPROACH* 3.*BIODUR*108* 4.*TI*GRADE*2*
23'
Biodur108*CORROSION*RESISTANCE*
5.*TI*GRADE*5* 6.*OTHERS* 7.*CONCLUSIONS*
100μm' 100μm'100μm'
Recuit_2
5mm800°C_1h_1
5mm800°C_2h
5mm
a)* c)*b)*
Figure*8:*Presence*of*nitrides*in*Biodur108*a)*in*the*annealed*state,**afer*a*heat4treatment*at*800°C*during*b)*1h*and*c)*2h*and*the*corresponding*resistance*to*piung*corrosion.**
1.*INTRODUCTION* 2.*EXPERIMENTAL*APPROACH* 3.*BIODUR*108* 4.*TI*GRADE*2*
23'
Biodur108*CORROSION*RESISTANCE*
5.*TI*GRADE*5* 6.*OTHERS* 7.*CONCLUSIONS*
100μm' 100μm'100μm'
Recuit_2
5mm800°C_1h_1
5mm800°C_2h
5mm
a)* c)*b)*
Figure*8:*Presence*of*nitrides*in*Biodur108*a)*in*the*annealed*state,**afer*a*heat4treatment*at*800°C*during*b)*1h*and*c)*2h*and*the*corresponding*resistance*to*piung*corrosion.**
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Shear&bands&
Tensile!reduction!in!area!ln!(A0/A)!
Cracking!reduction!ln(t0/t)!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
0!
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0! 100! 200! 300! 400!
Yiel
d!St
reng
th![M
Pa]!
Temperature![°C]!
Biodur108!
PM!(316L)!
0!
1!
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0!2!4!6!8!10!
Pow
er![k
W]!
Thickness![mm]!
25°C!100°C!200°C!400°C!
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Yiel
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Temperature![°C]!
Biodur108!
PM!(316L)!
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Pow
er![k
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Thickness![mm]!
25°C!100°C!200°C!400°C!
Effect of ductility Effect of strain state
Effect of reheatingPossible stress relief at the vicinity of the sample surface during reheating (450 - 700°C).
Effect of edge shapeno influence due to the edge shape observed, similar un-der cold and warm condi-tions.
oxygen-dislocations interaction
Warm rolling temperature: 200°C
For area reduction greater than 50%, maximum size of the edge crack is much lower, when using warm rolling.
→ Warm rolling provides a substantial gain over cold rolling.
!
5mm
Biodur_tiède_3mm_test3
5mm
TiG2_froid_2.1mm_test3
5mm
TiG2_tiède_2.1mm_test4
!
5mm
Biodur_tiède_3mm_test3
5mm
TiG2_froid_2.1mm_test3
5mm
TiG2_tiède_2.1mm_test4
Cold Warm
2h a
t 800
°C1h
at 8
00°C
→ 168h in FeCl3
→ 47h in FeCl3
→ 168h in FeCl3
nitrides precipitation at 800°C Pitting corrosion tests
N i t r i d e s prec ip i ta -tion at grain boundaries
N i t r i d e s prec ip i ta -tion within grains
1. INTRODUCTION 2. EXPERIMENTAL APPROACH 3. BIODUR 108 4. TI GRADE 2
7
FLAT ROLLING TESTS
5. TI GRADE 5 6. OTHERS 7. CONCLUSIONS
Typical cold rolling path: 10 – 8 – 7 – 6 – 5 – 4 – 3 !Typical warm rolling path: 10 – 7 – 5 – 3
Wire Flat oval
1. Process 2. Roll mill
• If roll mill power is a limitation:
P σy
• if edge cracking is a limitation2:
ln(t0 / t) ln (A0 / A)
∝
∝
Warm flat rolling is advantageous for:
• Ti Grade 2• Biodur108
Warm flat rolling is inefficient for:
• Ti Grade 5
issues related to warm rolling must be taken into account. For example:
• Effect of nitrides precipitation on Biodur108 corro-sion resistance
CHAllEnGEsLimiting factors in cold rolling
Cold rolling is a well-suited shaping process for many metals and alloys (e.g. austenitic and ferritic stainless steels, copper, alumi-nium, etc). some problems may however arise for certain classes of materials. Two main issues are commonly encountered:
METhODOLOGyhow to overcome these issues?
• Measure the evolution of the properties as a func-tion of temperature for three problematic materials currently used by Précimet sA1. Compare the re-sults to a reference (here: 316L stainless steel).
• Evaluate, whether a slight increase in the rolling temperature (typically 200 - 400°C) could overco-me issues encountered during cold rolling.
1 www.pxgroup.com
• Roll mills overload: it typically occurs for alloys having high initial yield strength and / or high work hardening rate, and thus require high stresses to be plastically deformed.
• Surface defects: edge cracking is the most com-mon defect. it typically occurs in alloys having li-mited ductility.
2 Cockcroft & latham, The effect of stress systems on metals workability, 1966.
3Kailas et al. Flow instabilities and fracture in Ti-6Al-4V de-formed in compression at 298K to 673K, 1994
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Maxim
um!crack!size![μ
m]!
Area!reduction![%]!
Maximum!crack!size!Y!cold!
Maximum!crack!size!Y!warm!I!
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1!
Y2! Y1.5! Y1! Y0.5! 0!
True
!tens
ile!st
rain
![Y]!
True!compressive!strain![Y]!
Ti!Grade!2!Y!diam!10!Y!cold!
Ti!Grade!2!Y!diam!10!Y!warm!
0!
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0! 100! 200! 300! 400! 500! 600!
Yiel
d!St
reng
th![M
Pa]!
Temperature![°C]!
Ti!Grade!2!
Ti!Grade!3!(litt)!
Ti!Grade!4!(litt)!
Ann
eale
d0.
5h a
t 110
0°C
Ductility has a positive in-fluence for T > 200°C
strain state has no influence, similar for both conditions
This interaction strength de-crease facilitates deformation.
A pass corresponds to a reduction from 10mm to the indicated thickness.
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Maxim
um!crack!size![μ
m]!
Area!reduction![%]!
Maximum!crack!size!Y!cold!
Maximum!crack!size!Y!warm!I!
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Area!re
duction![%
]!
Temperature![°C]!
!!!
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0!
0.1!
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1!
Y2! Y1.5! Y1! Y0.5! 0!
True
!tens
ile!st
rain
![Y]!
True!compressive!strain![Y]!
Ti!Grade!2!Y!diam!10!Y!cold!
Ti!Grade!2!Y!diam!10!Y!warm!
0!
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0! 100! 200! 300! 400! 500! 600!
Yiel
d!St
reng
th![M
Pa]!
Temperature![°C]!
Ti!Grade!2!
Ti!Grade!3!(litt)!
Ti!Grade!4!(litt)!
Elongation
Widening
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