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Rapid solidification and advanced
manufacturing of Cu-based shape memory
alloys with complex geometries
Piter Gargarella, Claudio S. Kiminami, Walter J. Botta, Alberto M. Jorge Jr. and Claudemiro Bolfarini
Federal University of São Carlos (UFSCar), Department of Materials Engineering (DEMa), Brazil
Simon Pauly and Tobias Gustmann
Institute for Complex Materials, IFW-Dresden, Germany
Slide 2
Contents
I. Motivation
- Why Cu-based SMAs and rapid solidification?
I. Project details/ project partners
- Project coordination
- Aim and project duration
- Summary of scientific outputs
III. Results
- Spray forming of Cu-based SMAs
- Phase formation, thermal stability and mechanical properties of Cu-based SMA produced by SLM
Slide 3
Motivation
youtube.com/watch?v=0K1niBUyAqY
The shape memory effect
Slide 4
Motivation
• Exhibit martensitic
transformation: the material
changes its structure, from a
low symetry structure
(martensite), stable at ↓T, to
a high simetric structure
(austenite), stable at ↑T.
• Shape Memory Effect.
• These alloys can show
superelasticity or
pseudoplasticity: large
recoverable strain up to 10 %.
K. Otsuka and K. Shimizu, International Metals Reviews (1986)
Shape memory effect
T TT
martensiteaustenite
Superelastic behaviour of a TiNi wire
J. Mohd Jani et al. Mat. and Design 56 (2014) 1078–11134
Slide 5
C. Cismasiu (ed.) Shape memory alloys, Rijeka:Sciyo, 2010
Active Bending Catheter
Ortodontic applications
Stent
Simon filter
Motivation
Slide 6
Cryofit
C. Cismasiu (ed.) Shape memory alloys, Rijeka:Sciyo, 2010M.H. Wu, L.M. Schetkz, Procedings of the ICSMT, 2000
Flexible Glasses
Rice cooker
Turbines
Car parts
Motivation
Slide 7
Motivation
• Cu-based vs TiNi-based
•Cu-based SMAs: good SM behaviour, higher thermal and eletricalconductivity, lower cost and are easier to process than traditional TiNi-based SMAs.
•Cu-Al-Ni: interesting for high temperature applications (100-200 oC).
•Coarse-grained Cu-based SMAs are intrinsically brittle
• Elastic anisotropy transgranular fracture
• Grain refinement: grain refiners (e.g. Ti, Zr, B, …), thermo-mechanical treatment, cooling rate
• Rapid solidification : avoid the formation of eq. phases: α, γ2 and NiAl.
• Novel methods: atomization, spray forming and sel. laser melting
• Selective laser melting: explore the effect of geometry
Cu-14Al-3.9Ni
Cu-14.9Al-4.1Ni
Cu-14Al-4Ni
Cu-13.2Al-3.8Ni
S. Miyazaki, Trans JIM 1981
loaded unloaded
Slide 8
8
Phase 1 (01.01.2013 – 31.03.2015):
i) Produce Cu-based SMAs by spray forming and gas atomisation;
ii) Use SLM to consolidate the powders obtained;
iii) Characterize the samples produced.
Phase 2 (01.08.2016 – 31.07.2020):
i) Optimize SLM, atomization and spray forming process parameters;
ii) Investigate the formation of oligocrystalline structures by SLM;
iii) Understand the transformation behaviour by means of thermal and mechanical treatments.
Aim and Project Duration
Project details/ project partners
Slide 9
9
Rapid Solidification and advanced manufacturing of Cu-based shape
memory alloys with complex geometry
Expertise in the field of spray forming/gas atomisation
Long-standing experience regarding the investigation and characterisation of metastable materials and their thermo-mechanical properties
Know-how in terms of selective laser melting
+
Dr. S. Pauly
T. Gustmann, PhD stud.
Prof. Dr.-Ing. Piter Gargarella
Prof. Dr.-Ing. Cláudio S. Kiminami
Prof. Dr. Walter José Botta Filho
Prof. Dr.-Ing. Claudemiro Bolfarini
Prof. Dr. Alberto M.Jorge Jr.
Dr. Régis Cava, Post-doctorate
Murillo Romero, PhD stud.
Witor Wolf, PhD stud.
Rodolfo Batalha, PhD stud.
Bianca C. Arantes, undergrad.
Student
Project details/ project partners
Slide 10
Project details/ project partners
-Exchange of samples and results
-Exchange of six students (4 intern. undergrad. + 2 master/PhD thesis)
-3 PhD dissertations + 2 Master thesis
-Several visits to São Carlos/ Dresden (2 Germany → Brazil, 7 Brazil →
Germany)
-Participation in conferences (> 15) + publications (10)
Project outputs:
Slide 11
Spray Forming
• The gas atomizer a melt stream producing droplets that are colected by a substrate producing a deposit.
• Higher cooling rates during solidification:smaller grains with a lower level of microstructural segregation.
• Mean parameters:- Massic Gas/Metal ratio (GMR);- Fligh droplets distance;- Gas pressure;- Nooze design and dimensions- Shape and material´s substrate and
its movement.
Spray forming of Cu-based SMAs
Slide 12
Parameters used during spray forming
Parameter Cu-11.85Al-3.2Ni-3Mn Cu-11.35Al-3.2Ni-3Mn-0.5ZrAmount of material 5.2 kg 7.8 Kg
Liquidus temperature 1060 °C 1160 °CEjection temperature 1280 °C 1310 °C
Gas N2 N2
Atomisation pressure 0.5 MPa 0.5 MPaDiameter of nozzle 6 mm 6 mm
Flight distance 380 mm 380 mmGas-to-metal ratio (GMR) 1.94 1.94
Substrate rotation 60 rpm 60 rpm
Spray forming of Cu-based SMAs
Slide 13
Effective diameter and height of 150 mm and 75 mm respectively.
Sketch of the transversal section indicating the analyzed regions: Bottom. central and peripheral
regions.
Cu-11.85Al-3.2Ni-3Mn (%wt)
Cu-11.35Al-3.2Ni-3Mn-0.5Zr (wt%)
Spray forming of Cu-based SMAs
R. Cava, P. Gargarella et. al. submitted to Acta Materialia 2017
Slide 14
• Only the monoclinic martensite β’ phase (zigzag morphology)was observed.
• nanometric twins.
• Dureza: 190 ± 15 HV1.0
• Equiaxed grains with size of 135 ± 20 μm. Porosity around 0.87 ±0.09.
Cu-11.85Al-3.2Ni-3Mn (%wt)
100 nm
Spray forming of Cu-based SMAs
R. Cava, P. Gargarella et. al. submitted to Acta Materialia 2017
Slide 15
Cu-11.35Al-3.2Ni-3Mn-0.5Zr (wt%)
• Monoclinic martensite β’ phase (zigzag morphology) formed togetherwith a Cu-rich phase at the grain boundary.
• Equiaxed grains with size around 28.7 ± 1.5 μm. Porosity around 0.03± 0.04.
• Dureza: 361 ± 10 HV1.0
• Nanometer-sized martensitic laths, around five times smaller than theobserved for the Cu-11.85Al-3.2Ni-3Mn alloy.
Spray forming of Cu-based SMAs
R. Cava, P. Gargarella et. al. submitted to Acta Materialia 2017
Slide 16
DS
C (
a.u
.)
← cooling
heating →
Temperature (⁰C)
DS
C h
ea
tfl
ow
(a.u
.) e
xo As
Af
Mf Ms
Spray forming of Cu-based SMAs
Slide 17
17
Sample Fracture strength (MPa) Yield strength (MPa) Fracture Strain (%)
CP1 550 298 4.0
CP2 525 296 3.9
CP3 500 240 4.1
Mean/Std. Dev. 525 ± 25 278 ± 33 4.00 ± 0.1
Ref [1] 380 - 560 200 4.5 - 5.5
Ref [2] 625 280-300 6 – 7
[1] Roh et al., Materials Science and Engineering, 1991.[2] Morris et al., Acta metall, mater., 1994.
Cu-11.85Al-3.2Ni-3Mn (%wt)
Spray forming of Cu-based SMAs
R. Cava, P. Gargarella et. al. submitted to Acta Materialia 2017
Slide 18
Cu-11.35Al-3.2Ni-3Mn-0.5Zr (wt%)
18
Sample Fracture strength (MPa) Yield strength (MPa) Fracture Strain (%)
Tambient - 1 980 380 5.25
Tambient - 2 950 350 5.05
Mean/Std. dev. 965 ± 21 365 ± 21 5.1 ± 0.1
[Ref 1] Tambient 750 200 7.5 – 8.0
[Ref 2] Tambient 625 280-300 6 – 7
T= 220 °C 880 600 6.65
[Ref 2] T = 200 °C 750-800 270-280 7-8
[1] Roh et al., Materials Science and Engineering, 1991.[2] Morris et al., Acta metall, mater., 1994.
Spray forming of Cu-based SMAs
R. Cava, P. Gargarella et. al. submitted to Acta Materialia 2017
Slide 19
Microstructure of Cu-11.35Al-3.2Ni-3Mn-0.5Zr (wt%) after heat Treatment at 850 °C/30 min
Spray forming of Cu-based SMAs
Grain size:32.5 ±5 μm
Hardness (HV1.0): 284 ± 10
R. Cava, P. Gargarella et. al. submitted to Acta Materialia 2017
Slide 20
Microstructure of Cu-11.35Al-3.2Ni-3Mn-0.5Zr (wt%) after heat Treatment at 850 °C/30 min
Spray forming of Cu-based SMAs
Slide 21
200 nm
ElementNominal
composition Matrix Precipitate
Cu 81.95 83.67 76.73
Al 11.35 8.03 8.13
Ni 3.20 3.33 5.71
Mn 3.00 3.37 2.38
Zr 0.50 1.60 7.05
Total 100.0 100.0 100.0
Microstructure of Cu-11.35Al-3.2Ni-3Mn-0.5Zr (wt%) after heat Treatment at 300 °C/1 day
Y phase: Cu2AlZr cubic
Spray forming of Cu-based SMAs
Grain size: Hardness (HV1.0): 27 ± 3 μm 368 ± 9
Slide 22
2250 100 150 200
Temperature (ºC)
DS
C (
a.u
.)
-120 -70 -20 30 80 130
Temperature (ºC)
DS
C (
a.u
.)
ConditionHT Time
(Min)As(ºC)
Af (ºC)
Ms (ºC)
Mf (ºC)
Af - Ms (ºC)
As-cast - 84.4 161.6 105.9 49.3 55.7
300 ºC 1440 -4.4 36.7 -31.7 -75.4 68.4
850 ºC 30 134.2 179.2 138.9 76.9 40.3
As cast
HT: 300 ºC/1 day
HT: 850 ºC/30 min
Heating
Exo
Cu-11.35Al-3.2Ni-3Mn-0.5ZrHeat/cooling rate:
20 K/min
Spray forming of Cu-based SMAs
Slide 23
SampleTensão
máxima (MPa)Yield Stress
(MPa)Deformação até
ruptura (%)
As-Cast 936.51 426.27 5.25
850°/30 min 912.38 383.14 7.52
300°/1 day 856.96 590.54 3.24
Roh et al. [2] 380 - 560 200 4.5 - 5.5
Morris et al. [12] 625 280-300 6 – 7
0
250
500
750
1000
0 1 2 3 4 5 6 7 8True Strain (%)
Tru
e S
tre
ss
(M
Pa
)
300 ºC/ 1 day 850ºC/30 min As Cast
Cu-11.35Al-3.2Ni-3Mn-0.5Zr
Spray forming of Cu-based SMAs
tensile tests
Slide 24
24
A strong influence on grain size, thermal stability and mechanical behaviour was observedwith small addition of Zr to a spray formed Cu-11.85Al-3.2Ni-3Mn (wt%) SMA.
The grain size decreases almost 5x, reaching sizes usually observed only afterthermomechanical processing.
The addition of Zr also changes the mechanical behaviour, increasing the tensile ductilityand improving the work-hardening behaviour. The fracture strength increases almost twotimes (at room temperature) when compared with the alloy without Zr.
The transformation temperatures of the Zr-added SMA are very sensitive to thermaltreatments.
By controlling the process parameters and carrying out post-treatments, the new Cu-Al-Ni-Mn-Zr alloy can be design to different applications.
Spray forming of Cu-based SMAs: conclusions
Slide 25
S. Pauly, Mater Today 2013
• Layer-by-layer process, small liquid volumes
• High intrinsic cooling rates metastable phases/microstructures
• Cu-11.85Al-3.2Ni-3Mn and Cu-11.35Al-3.2Ni-3Mn-0.5Zr
• Zr: grain refiner
• Relative density: 98.8 – 99.8%
• Suction casting (rapid quenching) for comparison
• Role of Zr on microstructure and SME?
• Effect of annealing?
• Effect of processing on SME?
Phase formation, thermal stability and mechanical properties of Cu-based SMA produced by SLM
Slide 26
Cu-11.85Al-3.2Ni-3MnCu-11.35Al-3.2Ni-3Mn-0.5Zr
• β1’ is the main phase
• Unambiguous phase identification aggravated: broad peaks, multitude of phases
• Annealing treatment: 850 °C for 10 min (water quench) + 300 °C for 60 min (cooling in air)
• After annealing: β1, α(?) and γ1’(?) and additional phase
EDX
EBSD
Phase formation, thermal stability and mechanical properties of Cu-based SMA produced by SLM
T. Gustmann, S. Pauly et. al. Shap. Mem. Superelasticity 2016
Slide 27
Cu-11.85Al-3.2Ni-3Mn (cast, centre) Cu-11.35Al-3.2Ni-3Mn-0.5Zr (cast, centre)
Cu-11.85Al-3.2Ni-3Mn (SLM) Cu-11.35Al-3.2Ni-3Mn-0.5Zr (SLM)
27Phase formation, thermal stability and mechanical properties of Cu-based SMA produced by SLM
T. Gustmann, S. Pauly et. al. Shap. Mem. Superelasticity 2016
Slide 28
Cu-11.4Al-2.5Ni-5Mn-0.4Ti
• Cu2ZrTi (X phase) in Cu-Al-Ni-Mn-Ti
• Cu2AlZr (Y phase, isomorphous to the X phase)
• Y phase very fine in as-prepared state
• Y phase coarsens after annealing can be identified by EBSD
• No hints of α, γ2 or NiAl
• Effect of Y phase during annealing?
4 µm
28
J. Dutkiewicz, MSEA 1999
cast Cu-11.35Al-3.2Ni-3Mn-0.5Zr, annealed
Cu2AlZrβ1‘
Phase formation, thermal stability and mechanical properties of Cu-based SMA produced by SLM
T. Gustmann, S. Pauly et. al. Shap. Mem. Superelasticity 2016
Slide 29
• Transformation temperatures with Zr additions
• No compositional gradients across the samples
• Fine Y phase: jerky transformation
• Fine Y phase: increase in MT temperatures
• Zr segregates at the boundaries when cooling rate
• Annealing: coarse Y phase at grain boundaries
no more MT
29
T. Tadaki in Shape memory materials, 1998
Cu-11.35Al-3.2Ni-3Mn-0.5Zr
Phase formation, thermal stability and mechanical properties of Cu-based SMA produced by SLM
T. Gustmann, S. Pauly et. al. Shap. Mem. Superelasticity 2016
Slide 30
• Typical double yielding
• Significant plastic strain in compression
• SLM comparable to casting
• Ductility of SLM samples exceeds that of cast samples
• Annealing increases strength and reduces ductility
presence of coarse Y phase
30
compression tension
Phase formation, thermal stability and mechanical properties of Cu-based SMA produced by SLM
Slide 31
SLM produces refined grains
Zr leads to precipitation of Y phase (Cu2AlZr)
Very fine Y phase during SLM (also inside grains)
Segregation of Zr at grain boundaries (cooling rate dependent)
preferential formation of Y phase during annealing
pinning of interfaces (grain refinement)
SLM samples: mechanical properties comparable to cast samples
Pseudoelasticity significantly reduced when Y phase is present
Coarse Y phase better recovery
Energy dissipated during SLM , transformation temperatures
Via SLM, the transformation properties can be adjusted
No need for additional thermo-mechanical post-treatments
31Phase formation, thermal stability and mechanical properties of Cu-based SMA produced by SLM: conclusions