shape memory alloys and its applications.

1. Ch .Surya prakasarao
Roll no:155574
Materials Technology
Shape Memory Alloys and Applications

2. Contents :-
SHAPE MEMORY ALLOYS HISTORY
• INTRODUCTION TO SMA
• MECHANISM OF SMA
• NiTiNOL (SMA)
• MANUFACTURING
• NiTiX HTSMA
• NiTiPd HTSMA
• APPLICATIONS
• MERITSAND DEMERITS
• SUMMARY

3. History of shape memory alloys
 The first reported steps towards the discovery of the shape-
memory effect were taken in the 1930s by Otsuka and wayman.
 Greninger and Mooradian (1938) observed the formation and
disappearance of a martensitic phase by decreasing and increasing
the temperature of a Cu-Zn alloy.
 The basic phenomenon of the memory effect governed by the
thermoelastic- behavior of the martensite phase was widely
reported a decade later.
 The nickel-titanium alloys were first developed in 1962–1963 by
the United StatesNaval Ordnance Laboratory and commercialized
under the trade name Nitinol (Nickel Titanium Naval Ordnance
Laboratories).
 shape-memory polymers have also been developed, and became

4. Introduction to SMA
 Smart or intelligent materials are materials that have to respond to
stimuli and environmental changes and to activate their functions
to these changes.
 The stimuli like temperature, pressure, electric flow, magnetic flow,
mechanical, etc can originate internally or externally.
 Shape memory alloys are smart materials.
 Shape-memory alloys (SMAs) are a unique family of metals
exhibiting an ability to recover macroscopic deformation introduced
at low temperature simply by heating the material through a
transformation temperature.
 Shape-memory effect (SME) is therefore the ability of a material to
return to a pre-set shape upon finishing the transformation.
 The same alloys exhibiting SME also to some extent exhibit
superelasticity.

6. SMA
Example: Copper-Aluminum-
Nickel,
Copper-Zinc-Aluminum,
Iron- Manganese-Silicon
and
Nickel-Titanium alloys
Ni-Ti-Pd
Ni-Ti-Hf

7. MECHANISM
 SME occurs due to the change in the crystalline structure of
materials.
 Thermoelastic martensitic transformation between high temparature
austinite to low tempareture martensite.
 Two phases are:
 Martensite:
• Low temperature phase
• Relatively weak
 Austenite:
• High temperature phase
• Relatively strong

8. MARTENSITE
DEFORMING
MARTENSITE
DEFORMED
MARTENSITE
AUSTENSITE
MARTENSITE

9. •Martensite to Austenite
transformation occurs by
heating.
•Austenite to Martensite
occurs by cooling.

10. characterstics:
 Phase transformation is reversible
 Diffusionless transformation
 Atoms moves less than one lattice parameter(coordinated
moment).
 The parent phase (austinate) is always ordered compound.

12. One-way vs. two-way shape memory
 Shape-memory alloys have different shape-memory effects. Two
common effects are one-way and two-way shape memory.

13. SMA phases and crystal
structures

14. Superelasticity:
• SMAs also display superelasticity, which is characterized by recovery of unusually
large strains. Instead of transforming between the martensite and austenite
phases in response to temperature, this phase transformation can be induced in
response to mechanical stress
• This transformation can only occur in a temperature range where the critical
stress for slip is greater than the critical stress for martensitic shear.

15. Methods for Determining Transformation
Temperatures
• The temperatures are commonly referred to as the martensite start (MS),
martensite finish (MF), austenite start (AS), and austenite finish (AF).
• It is important to know these temperatures so that the alloy can be effectively used
for a specific application. The thermal hysteresis (H), or difference in temperature
between the AF and MS temperatures.
• METHODS
1. differential scanning calorimeter
2. Bend force recovery test
3. Constent load dilatometry

16. • Differential scanning calorimetry (DSC) measures the heat transfer
between a sample of the material and its surroundings as a function of
temperature as it is heated and cooled through the transformation.
• Bend free recovery test (BFR), is often used to measure transformation
temperatures, but is limited to measurement of only the reverse
transformation.
• Load-bias testing, also known as Constant load dilatometry (CLD) can
be used to measure transformation temperatures in a more realistic
setting

18. Mechanical Testing
 Monotonic Isothermal Tension Tests
 Load-Bias Tests
 Training
MANUFACTURE:
Shape-memory alloys are typically made by casting, using
vacuum arc melting or induction melting. These are specialist
techniques used to keep impurities in the alloy to a minimum and
ensure the metals are well mixed.

19. NiTinol: (Ni-Ti)
 It Was discovered in Naval Ordnance Laboratory (NOL), Maryland, USA
 Ni- 50% , Ti- 50%
• NiTi, the high temperature B2 austenite phase transforms directly to monoclinic
B19' upon cooling through the transformation, which reverts directly to B2
austenite upon heating.
• Binary NiTi has a useable transformation temperature (Ms) range from subzero to
approximately (Af) 70 °C.
• Nitinol has many properties desirable for actuators, including small hysteresis
temperature, high work output, stable microstructure, and excellent corrosion
resistance.
• Rapid manufacturing using lasers.
• Steps:
design cad&cam,deposition on other materials.

20. Guide Laser
• Marking the
trajectory
• ƛ=605nm
• Red color
laser
Nozzle
• Laser nozzle
dia.= 3.29mm
• Powder feed
nozzle
dia.=1.96mm
Deposition
• Melting of
powder by
power laser
(IR)
ƛ=1080nm
• Power of
laser= 700W
Experimental setup
Ni + Ti powder
Ni
Ni Ti
Powder
Feeder
• High power Laser
• 5 axes manipulator
with CNC control
• Argon atmosphere
(965 mbar)
• No moisture!!
Closed
loop
process
control

21. NiTiX (HTSMA)
 To meet the need, several ternary alloy systems such as NiTiAu,
NiTiHf, NiTiPd, NiTiPt, and NiTiZr, have been evaluated.
 Research conducted consisted mainly of a determination of
transformation temperatures as a function of alloy content, and no-
load recovery tests to determine shape-memory behaviour.
 Transformation temperatures decrease or remain relatively
unchanged up to approximately 10 at.% ternary addition. At contents
>10 at.%, transformation temperatures increase linearly in relation to
ternary addition.
 Substitute for nickel, this increase in temperature continues until 50
at.% addition at which point the system becomes TiX.
 Substitute for titanium, transformation temperatures were only
improved by additions up to approximately 20 at.%, above which the
microstructure is no longer single phase.

23. NiTiPd (HTSMA)
 While not as effective as platinum additions in increasing the
transformation temperatures.
 NiTiPd more desirable due to the large difference in material price
between expensive platinum and the more economical palladium.
 NiTiPd alloys are more stable than Hf, Zr, and HfZr alloyed NiTi alloys with
regard to microstructure and transformation temperature when thermally
cycled.
 Five different ternary Ni49.5-XTi50.5PdX alloys (x = 15, 20, 25, 30, 46)

24. APPLICATIONS
 Medicine
 Optometry
 Engines
 Aerospace
 Robotics
 Automotive
 Pipings
 Civil stuctures
 Water spinkers
 Textile

25. Merits and Demerits
merits demerits
Bio-compactibility
Simplicity
Safty mechanism
Light weight
High corrosion resistens
More expensive
Complex control
Poor fatigue property
Heat dissipation

26. Conclusion:
 Today, the most promising technologies for efficiency and improved reliability
include the use of shape memory alloy materials and structures. Understanding
and controlling the composition and microstructure of SAM materials are the
ultimate objectives of research in this field, and is crucial to the production of
good SAM materials.
 New and advanced SMA will definitively enhance properties.

27. Refrences
 Glen S Bigelow, Effects of Palladium Content, Quaternary Alloying, and
Thermomechanical Processing on the Behaviour of Ni-Ti-Pd Shape
Memory Alloys for Actuator Applications, NASA/TM—2008-214702.
 Jaronie Mohd Jani , Martin Leary a, Aleksandar Subic a, Mark A. Gibson,
A review of shape memory alloy research, applications and opportunities,
Materials and Design 56 (2014) 1078–1113.
 GLEN S. BIGELOW, SANTO A. PADULA II, ANITA GARG, DARRELL
GAYDOSH, and RONALD D. NOEBE, The Minerals, Metals & Materials
Society and ASM International 2010
 Masamine Imahashi a, M.ImranKhan a, HeeYoungKim a,n,
ShuichiMiyazaki, The effect of Pd content on microstructure and shape-
memory properties of Ti–Ni–Pd–Cu alloys, Materials Science &
Engineering A602(2014)19–24

28.  P.K. KUMAR AND D.C. LAGOUDAS, “Introduction to Shape
Memory Alloys”, D.C. Lagoudas (ed.), Shape Memory Alloys, DOI:
10.1007/978-0-387-47685-81,©Springer Science+Business Media,
LLC 2008.
 Darel E. Hodgson, Shape Memory Applications, Inc., Ming H.
Memry Corporation, and Robert J. Biermann, Harrison Alloys, Inc., “
Shape Memory Alloys”, ASM Handbook, Volume 2: Properties and
Selection: Nonferrous Alloys and Special-Purpose Materials, ASM
Handbook Committee, p897-902 Copyright © 1990 ASM
International® All rights reserved. www.asminternational.org
 Callister’s “Materials Science and Engineering” Second Edition,
Adapted by R. Balasubramaniam, Page no. 266.