1. Titanium and Titanium Alloys Properties ME 296T Fall 2016 Ghazwan Al qaraghuli Ahmed Kadhim Nestor Ramos

2. Outline  Physical Properties of Titanium  Microstructure Phases and Properties  Heat Treatments and Ageing  Titanium Alloy Application  Casting Vs Forging  Titanium Alloys in Elevated temperature  Titanium Alloys in Jet Engine  Titanium Alloys Mechanical Properties  Fatigue Resistance

3. Introduction  Ti not found in its free pure metal form in nature but as oxides, ilmenite (FeTiO3) and rutile (TiO2) is called Commercial pure (CP-Ti).  (CP-Ti) contains elemental titanium plus some amount of impurities such as Nitrogen (N), Hydrogen (H), Oxygen (O), and Iron (Fe). FeTiO3 TiO2

4. Physical Properties of Titanium  Titanium alloys are usually divided into three categories: alpha (α ), alpha-beta (α+β) and beta (β).  Pure titanium has hexagonal close packed structure (hcp) in Low or room Temperature and is body-centered cubic (bcc) High temperature (882).

5. Microstructure Phases and Properties  Commercially pure (CP) titanium alpha and near alpha titanium alloys - Generally non-heat treatable and hard to weald - Medium strength, good creep strength, good corrosion resistance  Alpha-beta titanium alloys - Heat treatable, good forming properties - Medium to high strength, good creep strength excellent ability to be forge.  Beta titanium alloys - Heat treatable and readily formable - Very high strength, low ductility Microstructure for Ti alloy

6. Heat Treatments and Ageing There are four common heat treatments used for Ti-6A-4V: 1. Mill anneal (MA or A) -- this is the most common heat treatment. 2. Re- crystallize anneal (RA) -- this is a more damage tolerant heat treatment condition. 3. Beta anneal (BA) -- this is used with both the standard and ELI grades. For maximum damage tolerance properties. 4. Solution treated and aged (STA) -- provides the maximum strength, but full hardenability is limited to about 25 mm

7. Microstructure Phases and Properties  Near α alloys contain α-phase and usually less than 10% of β phase and has good creep resistance.  The β phase improves the strength and workability of the alloys.  (α + β ) alloy promotes equilibrium between higher strength of β alloys and creep resistance of α alloys.

8. Heat Treatments and Ageing Heat Treatment and elements effect for each phase (a) α phase and β stabilizer (b) β phase and α stabilizer

9. Composition and Applications of α+β titanium Alloys

10. Titanium Alloy Application  Titanium alloys are becoming a more common replacement to Ni super alloys in aircraft because of their high-strength to weight ratio.  In aircraft engines there are several applications for Titanium alloy (fans and compressor parts ) because of higher temperatures.  Forgings and heat-treatment made titanium alloys have various characterization.  Fatigue resistance of titanium after heat treatment and aging is greater than that of aluminum or steel.  Good workability  Good fabrication ability

11. Ti- Alloy(α+β) Properties after Heat Treatment and Aging

12. Casting Vs Forging Forging  Forged alloy is stronger and more ductile than its cast equivalent in the unexposed condition.  Forged having significantly higher strength with both the UTS and stress value. Casting Casting found extensive application  Reduce the microstructuring cycle cost and time.  Acceptable quality and and strength level.  Lower weight and part count.  Eliminating weld and associated preps.

13. Titanium Alloys in Elevated temperature  Most of the engine parts which are exposed to higher temperatures are usually made of titanium alloys.  Purpose  Light weight material with high strength.  Thousands of operating hours at temperatures up to (1100 °C).  High mechanical stresses due to high rotational speeds and large aerodynamic forces.  Longer Operating Lifetime.  Time, temperature and stress dependent on effects such as creep, stress rupture, and high- and low-cycle fatigue.  Corrosion/oxidation resistance. Distribute Titanium alloys in Jet engine vs temperature

14. Cold Section Components  Typical Alloys: Ti-6Al- 4V&Ti6246  Use for Fan disks/blade Hot section components  Typical Alloy : Ti 834  Use for compressor disks Titanium Alloys in Jet Engine

15. Titanium Alloys Mechanical Properties

16. Ti-834 ( 5.8Al - 4Sn - 3.5Zr - 0.7Nb - 0.5Mo - 0.35Si - 0.06C ) increased tensile strength and creep resistance up to 600°C together with improved fatigue strength. low coefficient of expansion High temperature resistance (850 -1100) °C. High melting point of from (1500 to1735) °C.. High resistant for (fatigue, creep-rupture @ High Temperature ).

17. Ti 6Al-4V  Used for low pressure environments (fan).  High-cycle fatigue static and high reliability is required for the rotating disks.  increases substantially with increases strain and with increasing strain rate,but decreases with increasing temperature.  Good creep resistant,High yield strength.  High Stiffness and High Density.  High Strength.  Low Thermal conductivity.  Fatigue endurance.  High rotation with high speed. Ti6246  High fatigue properties and improved creep resistance over Ti6-4,Use For mid- pressure compressor disks.  High fatigue strength and excellent toughness.

19. Alpha-Alloys- Timetal 834  Creep deformation- 600C  Low to medium strength  Good notch toughness  Well ductility  Mechanical properties at cryogenic temperatures  Highest corrosion resistance  Optimum high temperature creep resistance  Oxidation resistance  Silicon

20. Improve alpha- alloys  Longer time at the solution heat temperature (30- 240 minutes)  Ageing treatment is increased  Add Silicon  For example-Ti 834-ageing treatment- a fine dispersion of (Ti5) Si3, Zr5 Si3 improves its creep properties.  It helps by precipitate out of the solid solution at dislocation sites during deformation.  Precipitation amount-Ageing cycle

21. Silicon-The Great Direct correlation-% of Si and Creep Resistance Higher % Si→ σ UT →Elongation (%) Higher % Si →Creep resistance

22. Example- Titanium 17 Double Solution Treatment Acicular alpha phase Forging Low Temperatures (below 450), Statics

23. Alpha-Beta Alloys  Alpha-beta strength  Heat Treatment and Aging  Least Creep Resistant  Heavy duty purposes (Higher Yield Strengths)  Maximum operated temperature under creep conditions normally is 300-450 c.  Near alpha alloys heat treated in the alpha-beta phase field. 450-500°C  Near alpha alloys heat treated in the beta phase field. 600°C.

24. Fatigue Resistance  Cycle at high Temperatures →Low silicon → rapid cooling = Cracking.  For the higher silicon content alloy, many more cracks were present in the scale, and the scale was observed to be much more porous.  LCF life depending on the the grain size and microstructure and heat treatment.  (α+β) alloy in α stabilizer has less LCF in room temperature, This reduction in fatigue life is due to enhanced planarity of slip resulting from shearing of the phase precipitates.

25. Fatigue Resistance  In beta titanium, 3wt%Si can be dissolved at the eutectic temperature, 1339 °C. At 865 °C, the eutectic transformation β+α Ti3Si occurs.  For the higher silicon content alloy, many more cracks were present in the scale, and the scale was observed to be much more porous

26. Summary  Titanium alloy is one of the most used metals in jet engines due to its strength properties to weight ratio  Titanium properties vary by heat treatment or element components

27. References Smith, W.F., Structure and properties of engineering alloys, second edition, 1993, McGraw-Hill, ISBN 0-70- 112829-8. PROPERTIES AND APPLICATIONS OF TITANIUM ALLOYS: A BRIEF REVIEW C. Veiga1, J.P. Davim2 and A.J.R. Loureiro3 PRreovp. Aerdtive.s Mantedra. Sppcil.ic3a2ti(o2n0s1o2f)t1it3a3n-iu1m48 Aircraft Gas Turbine Engines Operation, Components & Systems (Jet Propulsion) (Jet Rocked Propulsion) by J. VennardJ. Vennard [3]Development of a High Temperature Titanium Alloy for Gas Turbine Applications byGeraint Rhys Watkins p 115 2015 An overview on the use of titanium in the aerospace industry by R.R. Boyer 1996 1 IATA The IATA Technology Roadmap Report June 2009 Advances in Gas Turbine Technology Edited by Dr. Ernesto Benini Titanium and Titanium Alloys: Fundamentals and Applications Christoph Leyens (Editor), Manfred Peters (Editor) 2003 p 20Christoph LeyensManfred Peters Materials properties handbook : titanium alloys Author: Rodney Boyer; Gerhard Welsch; E W Collings; 1994. p440 Cyclic oxidation behavior of aluminide coatings on Ti-base alloy IMI-834 at 750 °C by D.K. Das, Z. Alam