1 Ph.D Scholar, SMMME, IIT Bhubaneswar, India (Alloy Design Group) 2, 3 Assistant Professor, SMMME, IIT Bhubaneswar, India Ritukesh Sharma 1 , Amritendu Roy 2 , Partha Sarathi De 3 DISCUSSION RESULTS INTRODUCTION Friction Stir Processing (FSP) of Aluminum alloys – pros and cons Need to develop new alloys for Friction Stir Welding/ Processing (FSW/P) OBJECTIVES CONCLUSION The Al−TiB 2 composite (as-cast and friction stir processed) exhibits much better corrosion resistance compared to Al−B and Al−SiC based composites. Both friction stir processed and the as-cast Al−TiB 2 based composite resists pitting corrosion. The annealed HEA forms a Mn-rich oxide scale and Al- rich oxide scale at 500 o C and 1000 o C respectively. The HEA exhibits better or comparable oxidation resistance than most of the conventional alloys. ALLOY DEVELOPMENT FOR FRICTION STIR WELDING AND PROCESSING Fig: Weld crack in AA6061 base plate during TIG welding (Courtesy: Welding Productivity). Fig: Variation of joint efficiency with heat flux for FSW of heat treatable Al alloys [1] . Choice for composite Fig: Engineering stress strain curves [3]. Fig: Global demand for composites [2]. Adverse effect of TiB 2 reinforcement Reinforcement using High Entropy Alloy (HEA) Fig: Stress strain curves with percentage of TiB 2 [4] . Fig: Al-7% CoCrFeMnNi composite with improved strength [5]. • Microstructure and corrosion property investigation of an as-cast and FSP Al-TiB 2 composite. • To investigate the oxidation property of an AlCuFeMn high entropy alloy. MATERIALS AND METHODS • Test plates prepared by in-situ stir casting process and Friction Stir Processed. K 2 TiF 6 (l) + KBF 4 (l) + Al (l) → TiB 2 (s) + AlB 2 (l) + Al 3 Ti (s) + K 3 AlF 6 (l) + KAlF 4 (l) (800 o C) • Polarization tests in 3.5 wt.% NaCl solution for corrosion. • AlCuFeMn High Entropy Alloy developed by arc melting and annealed at 900 o C under vacuum. • Investigation of microstructure and oxidation resistance of the HEA at 500 o C and 1000 o C for 50 hrs. Fig: SEM image of a) as-cast b) FSP Al-TiB 2 composite. b) Volume fraction • As-cast: TiB 2 ~ 5%, Al 3 Ti ~ 9.2% Grain size and Hardness • As-cast: 16.8 ± 2.4 μm, 61 ± 1 HV High hardness • Lower grain size. • Uniform distribution of TiB 2 and Al 3 Ti. Clustering in the composite occurs due to [6-7] • High interfacial energy between Al and TiB 2 . • Interface velocity lower than critical velocity. Fig: OIM image of a) as-cast b) FSP Al-TiB 2 composite. Fig: a) Tafel plots b) Cyclic polarization curves for as-cast and FSP Al-TiB 2 composite. Corrosion current and corrosion rate • As-cast: 2.03 ± 0.30 μA.cm -2 0.022 ± 0.004 mm.a -1 1. Corrosion property of Al-TiB 2 composite 2. Oxidation property of AlCuFeMn HEA Fig: SEM image of AlCuFeMn HEA oxidized at a) 500 o C b) 1000 o C for 50 hours respectively. Fig: a) OIM image of the HEA b) Relative mass change vs. time plot of the HEA after oxidation. Fig: EDS analyisis of a) and c) 500 o C and 1000 o C oxidized samples rich in b) Mn oxide d) Al oxide respectively . No pitting corrosion • In Al-TiB 2 composite, after immersion in ocean water at room temperature, TiB 2 forms an oxide layer of TiO 2 -H 2 O [11]. • Volume fraction of Al 3 Ti is small and homogeneously distributed. • Further improvement is done by FSP. Uniform corrosion • FSP sample less susceptible to corrosion than as-cast as higher fraction of low angle grain boundaries in FSP sample. Oxidation of AlCuFeMn alloy Fig: Schematic of the oxidation process at 500 o C and 1000 o C after 50 hours of exposure. Tool rotation speed: 660 rpm Traverse speed: 40mm/min REFERENCE [1] Mishra et al., Springer, 2014. [2] Salih et al. Mater. And Des., 2015, 86, pp. 61-71. [3] Narimani et al., Materi.Sci.and Eng. A, 2016, 673, pp. 436-444. [4] Lu et al., Scrip. Mater., 2001, 45, pp. 1017-1023. [5] Kumar et al., J. Alloy. And Comp., 2015, 640, pp. 421-427. [6] Youssef et al.,Composites, 2005, 36, pp. 747-763. [7] Chawla et al., Springer, 2006. [8] Majumadar et al., Surf. Coat. Tech., 2006, 201, pp. 1236-1242. [9] Pohlman S.L., Corrosion, 1978, 34, pp. 156-159. [10] Mosleh et al., Trans. Non Ferr. Met. Soc. China, 2016, 26, pp. 1801-1808. [11] Covino et al.,J. Less Comm. Metals, 1975, 41, pp. 211-224. ACKNOWLEDGEMENT During the experiments, the assistance of Mr. A. Dutta, Master’s student and Mr. L. Sathua, Scientific Assistant, IIT Bhubaneswar is greatly appreciated a) b) • FSP: TiB 2 ~ 4%, Al 3 Ti ~ 8.4% a) b) • FSP: 5.3 ± 2.3μm, 65 ± 2HV a) b) • FSP: 1.30 ± 0.20 μA.cm -2 0.014 ± 0.003 mm.a -1 b) a) Fe rich region A Cu rich region B a) b) a) b) c) d) Fig: Comparison of corrosion current of different composites with the studied composite.
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1Ph.D Scholar, SMMME, IIT Bhubaneswar, India (Alloy Design Group) 2, 3Assistant Professor, SMMME, IIT Bhubaneswar, India
Ritukesh Sharma1, Amritendu Roy2, Partha Sarathi De3
DISCUSSION RESULTS INTRODUCTION Friction Stir Processing (FSP) of Aluminum alloys – pros and cons
Need to develop new alloys for Friction Stir Welding/ Processing (FSW/P)
OBJECTIVES CONCLUSION The Al−TiB2 composite (as-cast and friction stir processed) exhibits much better
corrosion resistance compared to Al−B and Al−SiC based composites.
Both friction stir processed and the as-cast Al−TiB2 based composite resists
pitting corrosion.
The annealed HEA forms a Mn-rich oxide scale and Al- rich oxide scale at
500oC and 1000oC respectively.
The HEA exhibits better or comparable oxidation resistance than most of the
conventional alloys.
ALLOY DEVELOPMENT FOR FRICTION STIR WELDING AND PROCESSING
Fig: Weld crack in AA6061 base plate
during TIG welding (Courtesy: Welding
Productivity).
Fig: Variation of joint efficiency with heat flux for
FSW of heat treatable Al alloys [1] .
Choice for composite
Fig: Engineering stress strain curves [3]. Fig: Global demand for composites [2].
Adverse effect of TiB2 reinforcement
Reinforcement using High Entropy Alloy (HEA)
Fig: Stress strain curves with percentage of
TiB2 [4] .
Fig: Al-7% CoCrFeMnNi composite with
improved strength [5].
• Microstructure and corrosion property investigation of an as-cast and
FSP Al-TiB2 composite.
• To investigate the oxidation property of an AlCuFeMn high entropy
alloy.
MATERIALS AND METHODS • Test plates prepared by in-situ stir casting process and Friction Stir
Processed.
K2TiF6 (l) + KBF4 (l) + Al (l) → TiB2 (s) + AlB2 (l) + Al3Ti (s) + K3AlF6 (l) +
KAlF4 (l) (800 oC)
• Polarization tests in 3.5 wt.% NaCl solution for corrosion.
• AlCuFeMn High Entropy Alloy developed by arc melting and annealed
at 900oC under vacuum.
• Investigation of microstructure and oxidation resistance of the HEA at
500oC and 1000oC for 50 hrs.
Fig: SEM image of a) as-cast b) FSP Al-TiB2 composite.
b)
Volume fraction
• As-cast: TiB2 ~ 5%, Al3Ti ~ 9.2%
Grain size and Hardness
• As-cast: 16.8 ± 2.4 μm, 61 ± 1 HV
High hardness
• Lower grain size.
• Uniform distribution of TiB2 and Al3Ti.
Clustering in the composite occurs due to [6-7]
• High interfacial energy between Al and TiB2.
• Interface velocity lower than critical velocity.
Fig: OIM image of a) as-cast b) FSP Al-TiB2 composite.
Fig: a) Tafel plots b) Cyclic polarization curves for as-cast and FSP Al-TiB2 composite.
Corrosion current and corrosion rate
• As-cast: 2.03 ± 0.30 μA.cm-2
0.022 ± 0.004 mm.a-1
1. Corrosion property of Al-TiB2 composite
2. Oxidation property of AlCuFeMn HEA
Fig: SEM image of AlCuFeMn HEA oxidized at a) 500oC b) 1000oC for 50 hours respectively.
Fig: a) OIM image of the HEA b) Relative mass change vs. time plot of the HEA after oxidation.
Fig: EDS analyisis of a) and c) 500oC and 1000oC oxidized samples rich in b) Mn oxide d) Al
oxide respectively .
No pitting corrosion
• In Al-TiB2 composite, after immersion in ocean water at room
temperature, TiB2 forms an oxide layer of TiO2-H2O [11].
• Volume fraction of Al3Ti is small and homogeneously distributed.
• Further improvement is done by FSP.
Uniform corrosion
• FSP sample less susceptible to corrosion than as-cast as higher
fraction of low angle grain boundaries in FSP sample.
Oxidation of AlCuFeMn alloy
Fig: Schematic of the oxidation process at 500oC and 1000oC after 50 hours of exposure.
Tool rotation speed: 660 rpm
Traverse speed: 40mm/min
REFERENCE [1] Mishra et al., Springer, 2014.
[2] Salih et al. Mater. And Des., 2015, 86, pp. 61-71.
[3] Narimani et al., Materi.Sci.and Eng. A, 2016, 673, pp. 436-444.
[4] Lu et al., Scrip. Mater., 2001, 45, pp. 1017-1023.
[5] Kumar et al., J. Alloy. And Comp., 2015, 640, pp. 421-427.
[6] Youssef et al.,Composites, 2005, 36, pp. 747-763.
[7] Chawla et al., Springer, 2006.
[8] Majumadar et al., Surf. Coat. Tech., 2006, 201, pp. 1236-1242.
[9] Pohlman S.L., Corrosion, 1978, 34, pp. 156-159.
[10] Mosleh et al., Trans. Non Ferr. Met. Soc. China, 2016, 26, pp. 1801-1808.
[11] Covino et al.,J. Less Comm. Metals, 1975, 41, pp. 211-224.
ACKNOWLEDGEMENT During the experiments, the assistance of Mr. A. Dutta, Master’s student and Mr. L. Sathua, Scientific Assistant, IIT Bhubaneswar is greatly appreciated
a) b)
• FSP: TiB2 ~ 4%, Al3Ti ~ 8.4%
a) b)
• FSP: 5.3 ± 2.3μm, 65 ± 2HV
a) b)
• FSP: 1.30 ± 0.20 μA.cm-2
0.014 ± 0.003 mm.a-1
b) a)
Fe rich region A
Cu rich region B
a) b)
a) b)
c) d)
Fig: Comparison of corrosion current of different composites with the studied composite.
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