[3] B.S. Murty, Jien-Wei Yeh and S. Ranganathan, High-Entropy Alloys, ISBN: 978-0-12-800251-3. [4] Yeh, J.W., 2013a. Alloy design strategies and future trends ...
HIGH ENTROPY ALLOYS - INTRODUCTION, APPLICATIONS AND ITS PROCESSING
By Dr.S.SIVASANKARAN, Assistant Professor, Department of Mechanical Engineering, College of Engineering, Qassim University 1
OUTLINE OF PRESENTATION Introduction Broad Spectrum of HEAs – R & D
Conventional alloys Definition of HEAs
Major Benefits Properties & Applications
Synthesis & Processing of HEAs References
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INTRODUCTION
Fig. Historical evolution of Engineering materials [1]
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INTRODUCTION-Cont…
Fig. The explosion in the diversity of materials in the modern era [2]
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INTRODUCTION-Cont…
Fig. The explosion in the diversity of materials in the modern era [2]
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INTRODUCTION-Cont…
Fig. Year-wise publications in the area of HEAs [3]
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BROAD SPECTRUM OF HEAs – R&D
Fig. The materials hypertetrahedron for HEAs [3]
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CLASSIFICATION OF PHASE DIAGRAM Unary Phase diagram (1) Binary Phase diagram (2) Ternary Phase diagram (3) Quaternary Phase diagram (4) Quinary Phase diagram (5) Sexinary Phase diagram (6) Septenary Phase diagram (7) Octonary Phase diagram (8) Nonary Phase diagram (9) Denary Phase diagram (10 8
CONVENTIONAL ALLOYS
Fig. Schematic ternary and quaternary systems, showing regions of the phase diagram which are relatively well known (green) near the corners, and relatively less well known (white) near the center [4] 9
ENTROPY EFFECT IN CONVENTIONAL ALLOYS Equiatomic composition
S conf RX A ln X A X B ln X B
Fig. Configurational entropy reaching a maximum at the equiatomic composition in a binary system [3] 10
ENTROPY EFFECT IN HEAs ALLOYS
Sconf R ln N ; N No. of elements S conf RX A ln X A X B ln X B
Fig. Entropy of mixing as a function of the number of elements for equiatomic alloys in the random solution state [3] 11
DEFINITION OF HEAs ALLOYS Each high-entropy alloy contains multiple elements, often five or more in equiatomic or near-equiatomic ratios, and minor elements HEAs is that significantly high mixing entropies of solid solution phases enhance their stability as compared with intermetallic compounds, especially at high temperatures HEAs are preferentially defined as those alloys containing at least five principal elements, each having the atomic percentage between 5% and 35%. 12
DEFINITION OF HEAs ALLOYS Cont…
Fig. (A) Five components in equiatomic ratio before mixing and (B) mixing to form a random solid solution. Assume their atomic sizes are same [3] 13
DEFINITION OF HEAs ALLOYS Cont…
Figure 2.6 (A) Alloys world [3] and (B) materials world (excluding composite materials) based on configurational entropy [4] 14
FOUR CORE EFFECT OF HEAs ALLOYS High Entropy Effect - Stabilizes solid solution (almost single phase) (it deviate from Gibbs phase rule) Sluggish diffusion - Kinetic transformation low Sever lattice distortion - Crystal structure deformed Cocktail effect - Strength of HEAs > Avg. composing elements (it violate rule of mixture) 15
MAJOR BENEFITS AND HOW? Single phase FCC – Very ductile (Au, Ag) Single phase BCC – High yield strength (Fe, W) Mixture of FCC & BCC – High strength ductile materials Ex: AlCoCrFeNiTi – σy = 2.26 GPa, εp = 23% Well performance at high temp due to decreased
kinetics Excellent creep behavior as more stability
High corrosion resistance at elevated Temp 16
PROPERTIES AND APPPLICATIONS OF HEAs Engine materials - better elevated-temperature strength, - oxidation resistance
- hot corrosion resistance
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PROPERTIES AND APPPLICATIONS OF HEAs Cont… Light transportation materials - Strength - Toughness
- Creep resistance - Workability
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PROPERTIES AND APPPLICATIONS OF HEAs Cont… Functional coatings materials
- Better wear resistance -Anti-sticky
- Anti-finger print - Anti-bacterial - Aesthetics
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PROPERTIES AND APPPLICATIONS OF HEAs Cont… Superconductor materials (no electrical resistance, 0V)
- Higher critical temperature and - Critical current
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PROPERTIES AND APPPLICATIONS OF HEAs Cont… Golf club head
- Higher strength and - Resilience
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MECHANICAL BEHAVIOUR - EXAMPLE
- Doesn't yield up to 1100 Mpa - Ultimate tensile strength of 1400MPa - Hardness of the alloy is found as 477 HV
Fig. Compressive stress strain curve of (Fe20 Cu20 Al20 Ni20 Ti20) alloy 22
SYNTHESIS AND PROCESSING OF HEAs Arc Melting – Liquid state Mechanical Alloying – Solid state Sputtering – Gas state Rapid solidification – Liquid state Laser cladding & Electro deposition – Electrochemical
process 3D Printing – Laser Engineered Net shape (LENS) – Solid
state 23
RESEARCH FACILITIES TOWARDS HEAs AT QEC HEAs Synthesis - Controlled N2 Atmosphere Furnace (1100°C) - Controlled Ar Atmosphere Furnace (1100°C) (under Installing) - Mechanical Alloying (High-energy Ball mill) (Approved for Purchasing) (Nanomaterials, Nano-particles for nano-fluids etc…) Consolidation - Hot Extrusion dies - ECAP - Multi-axial forging (under establishing) Characterization - SEM (Under erection), OM, 3D Profile meter - Metallographic polishing set-up (Some facilities are there and some equipment's are under erection) Mechanical Testing - MTS UTM (200 kN), Drop-hammer test (under Installation) 24
REFERENCES [1] Yeh, J.W., Chen, S.K., Lin, S.J., Gan, J.Y., Chin, T.S., Shun, T.T., et al., 2004b, Nanostructured high-entropy alloys with multiple principal elements: novel alloy design concepts and outcomes. Adv. Eng. Mater. 6, 299-303
[2] Ashby, M.F., 2011. Materials Selection in Mechanical Design, fourth ed. Butterworth-Heinemann, Elsevier, Oxford, UK.
[3] B.S. Murty, Jien-Wei Yeh and S. Ranganathan, High-Entropy Alloys, ISBN: 978-0-12-800251-3 [4] Yeh, J.W., 2013a. Alloy design strategies and future trends in high-entropy alloys. J. Met. 65, 17591771.
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THANK YOU & QUESTIONS?
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