To do --
	Wear - expand the following --
	"The effect of diffusion hardening on fatigue should be evaluated. For biomedical applications the possibility of spalling should be investigated. Friction may be reduced."

	Table 0.
	
	Under "Nomenclature", document factors that affect performance.
		Temperature and cooling rate (from beta transus?.)
			See Williams "Nucleation and Diffusional Growth", p. 7
				
		Thermomechanical processing --> controls microstructure (Williams, p. 14)
			See Williams, section "Bi-Modal Microstructures" (p. 17); fig 20, p. 19
				"The most critical parameter in step I is the cooling rate from the homogenization temperature" (p. 17)
				"The deformation degree determines the texture intensity whereas the deformation mode (unidirectional rolling, cross-rolling, pancake forging, etc.) determines the texture symmetry (Figure 22)." (p. 18)
			--> Is there a "standard" thermomechanical processing method so that, when specifying Ti-6Al-4V from two manufacturers, the resulting performance should be the same? (Note: Chinese Ti-7Al-4Mo had much lower loss than U.S. version)
			Beyond current discussion scope.
		Annealing
		STA
	
	Timet - different quality levels (single melt, double melt) ==> different fatigue performance?
	
	E is same in tension and compression? If not, implications?
	
	Morrissey, Ryan - "Fatigue strength of Ti-6Al-4V at very long lives" [U/S tests] ==> need full reference
		http://www.sciencedirect.com/science/article/pii/S0142112305001799

	Ti-7Al-4Mo -
		Check density & give matweb ref.
		Graph modulus vs raw stock dia (Branson data).
		Q graph
		
	Timet electrostatic tests of wave speed in Ti bar - Ti-6al-4V or Ti-7Al-4Mo? (table 3) (text says "an undisclosed titanium alloy"). Give cyl bar dia and approx L & L of samples.

	"Ti-6Al-4V ELI is a higher-purity ("extra-low interstitial") version of Ti-6Al-4V, with lower specified limits on iron and the interstitial elements carbon and principallyÿoxygen. This yields superior toughness, especially at low temperatures."
	--> give ref.
	
	Ti-6al-4V - what does "ASTM grade 5" imply? Does it encompass ELI & STA?
	
	Explain (also define) STA. Explain lameller (lamellar?)vs equiaxed.
	
	Picture of gun drill.
	
	Misonix radial disks -
		Can use to calc Poisson's ratio? Must assume E? Or can iterate to get both?

	Salyers -
		- f of test Xdu
		- f or L of test samples

	Glossary define -
		STA (solution treated and aged)
		
	Move part of fatigue discussion to fatigue.html?
	
	Fatigue comparison of Ti-6Al-4v & Ti-7Al-4Mo, smooth & notched. Also, "fatigue notch sensitivity factor".
	
	Osgood -
		Fig 4.48, p. 441 - note large scatter for Ti-6al-4V (#2 data pts on the graph)
		p. 216 - Lists endurance limit to Ti-6Al-4V as 60ksi
	
	Somewhere is bar chart comparing fatigue of alpha-Ti to alpha-beta-Ti (much better).

Mason, Warren - 'Internal Friction and Ultrasonic Yield Stress of the Alloy 90 Ti 6 Al 4 V'
	"This type of performnce is characteristic of a non-linear spring which is softer at high amplitudes." p. 1926. See fig 2, p. 1927
	--> could be a cause of instability (singing)?

Williams - 'Chapter 1 - Microstructure and Mechanical Properties of Titanium Alloys'
	
	Titanium undergoes an allotropic phase tranformation at 882.5 øC, changing from a closed-packed hexagonal crystal structure (alpha phase) below, to a body-centered cubic crystal structure (beta phase) above this temperature. The exact transformation temperature is strongly influenced by interstitial and substitutional elements, therefore depending on the purity of the metal. (p. 1)
	
	The elastic moduli are decreasing almost linearly with increasing test temperature up to the transformation temperature. (p. 2)

	In general, commercial beta-Ti alloys exhibit E-moduli at RT in the range of 70 to 90 GPa, while a and a+beta Ti-alloys show values which are always above 100 GPa [11]. (p. 2)
	
	Alloying elements in Ti are classified into alpha or beta stabilizers on the basis of their effects on the alpha/beta transformation temperature or on their differing solubilities in the alpha or beta phases. The substitutional element Al and the interstitials O, N and C are strong astabilizers and are increasing the transus temperature with increasing solute content, as shown in the schematic phase diagrams in Figure 6. The beta-stabilizing elements are lowering the transus temperature. Those are distinguished into beta-isomorphous types (e.g. V, Mo, Nb, Ta) and beta-entectoid types (e.g. Mn, Fe, Cr, Co, Ni. Cn, Si, H). Examples of these two diagram types are also shown in Figure 6. In addition, there exist other elements, for example Zr and Sn, which behave more or less neutral or are slightly decreasing the transus temperature (Figure 6). Actual equilibrium phase diagrams for all of these systems can be found in [18]. (p. 6)
	
	Commercial titanium alloys are classified conventionally in three different categories as alpha, alpha+beta, and beta alloys according to their equilibrium constitution, which varies with the types and concentrations of alloy elements. This is shown in a schematical pseudobinary beta-isomorphous phase diagram in Figure 9. A listing of various commercial alloys, belonging to one of the three groups, is shown in Table 3. Commercial purity titanium having various amounts of interstitial oxygen to increase the yield stress and alloys with a stabilizers (Al, Sn) are of the hep crystal structure at low temperature and as such classified as a alloys. The majority of the commercial alloys in Table 3 belongs to the alpha+beta alloys. These alloys contain, in addition to the a stabilizer Al, also beta stabilizing elements such as V, Mo, Nb or Cr. These elements decrease the a/beta transformation temperature and increase the width of the alpha+beta phase field with increasing beta-solute content. Furthermore they lower the temperature, where the beta phase starts to transform by the martensitic process (Ms-temperature). With a further increase in beta stabilizing elements, beyond that content which lowers the Ms-temperture to RT, those alloys are then called metastable beta alloys. For these alloys the beta phase can be retained at RT even in large sections during air cooling. However, these metastable beta alloys can usually be tranformed to a alpha+beta mixture by isothermal aging. At even higher beta stabilizer contents the alloys are stable beta alloys, which cannot be transformed to an alpha+beta mixture by further heat treatments. (p. 7)
	
	Table 3 (p. 7) lists alloy designations -
		alpha-alloys -- CP (commercially pure), other
		alpha + beta alloys -- includes Ti-6Al-4V
		Metastable (beta-Alloys) -- includes Ti-10-2-3

	The microstructure of Ti alloys can be varied and controlled by thermomechanical processing. The nature and degree of microstructure control that can be obtained depends on the alloy class and type. (p. 14)
		
	In the two phase alpha+beta titanium alloys three distinctly different types of microstructures can be obtained by changing the thermomechanical processing route: a fully lamellar structure, a fully equiaxed structure, and a so-called duplex or bi-modal microstructure containing equiaxed primary alpha in a lamellar alpha+Beta matrix. (p. 17)

	In step IV the temperature is more important than the time (Figure 20) because the temperature being either below or above the Ti3Al solvus temperature determines whether age-hardening by Ti3Al particles occurs in the a phase or not. For example, for the Ti-6A1-4V alloy the Ti3Al solvus temperature is about 550 øC. This means aging at 500 øC will precipitate Ti3Al particles whereas a heat treatment at 600 øC or above will be only a stress relieving treatment. (p. 21)
	
	Fig. 39 shows the effect of cooling rate (water quenched vs air cooled) on fatigue of Ti-6242 [Fully Lamellar Microstructure] (p. 28)
	Also see SN fig 45, p. 32 (two bi-modal structures)
	
	Fig. 49: Influence of texture and test direction on HCF strength, Ti-6A1-4V (vacuum & air)
		See text description p. 34.
			TD = transversal test direction
			RD = rolling direction
			B/T and T = type of textures
		In air, RD gives better HCF than TD

	CP Titanium is 98 % or more alpha phase, the remaining being iron stabilized beta phase.
	Most applications for CP Titanium are not fatigue critical but, on occasion, a vibratory excitation can occur in a structure in a chemical plant due to pumps and other rotating machinery. In such cases, it is important to note that the crack nucleation stress is essentially proportional to the yield stress (see Figure 36) and the ratio of the fatigue strength (at 10? cycles) to the yield stress is essentially constant with a value of -0.73. Therefore, in applications where fatigue failure is possible due to vibratory excitation, it is advisable to use the highest possible yield strength. (p. 47)
	
	Today (in the western world at least) there are really only three high temperature titanium alloys in widespread use. These are: Ti-6-2-4-2, IMI-685, and IMI-834. The tensile and fracture toughness properties of these three alloys are shown in Table 9. By far, the largest application of these alloys is in the compressor section of aircraft engines. These alloys are attractive for this application because they have reasonably good density corrected strength and very good density corrected creep resistance. (p. 48)
	All modern aircraft engines have portions of the compressor that operate in th temperature range 325øC to about 575øC (p. 49)
	The creep strength of high temperature titanium alloys like Ti-6-2-4-2 is substantially better than that of the lower temperature, higher strength alloys such as Ti-17.
	
	For very high performance applications, such as rotating parts in jet engines, the material is typically remelted twice and the product is known as triple melt or premium quality rotor grade material. The third melt further improves the chemical homogeneity and achieves some additional refining to remove or minimize the presence of melt related defects which will be mentioned later. (p. 71)
	
	Table 10 shows other alloys that could be even more structurally efficient, but cost and lack of experience in designing with these other alloys has led to the continued principal use of Ti-6A1-4V. (p. 53)
	
	Fig. 72 shows cross-over of Ti fatigue curves for different mats as N increases (i.e., one mat that appears better at low N doesn't look as good at high N). (p. 55)
	
Lesuer, Donald - 'Experimental Investigations of Material Models for Ti-6Al-4V Titanium and 2024-T3 Aluminum' (high strain rate tests)
	The Ti-6Al-4V alloy evaluated in this study was purchased from RMI Titanium Company of Niles, Ohio in the form of a hot-rolled and annealed plate. The annealing heat treatment was done at 790øC for 1 hour followed by furnace cooling. Before testing, samples were annealed at 730øC for 1 hour and air cooled. The alloy was processed to conform to specification AMS 4911, which is typically used for Ti-6Al-4V for aircraft containment structures. (p. 3)
	The microstructure consists of roughly equiaxed alpha and transformed beta phase, which is a typical microstructure for the Ti-6Al-4V alloy manufactured to the AMS 4911 specification. (p. 3)

	Fig 1 shows anisotropic 3D etched microstructure.

'Titanium - A Technical Guide'
	"One further observation about titanium alloys is that fatigue data reported in the literature often may be on material with favorable surface residual stress induced by turning, milling, etc. Fully stress-relieved or chem-milled surfaces probably have fatigue strengths below the reported alloy capabilities, because the latter have been biased upward by the favorable - that is compressive - stresses." p. 117. See fig. 11.16

Mil-Hdbk-697A
	"The fatigue properties of titanium and its alloys, while being of the most importance in many applications, are seldom if ever described in specifications. Possibly this is because there are so many variables associated with the fatigue performance of a material that it is difficult to predict the behavior except within broad limits. The material variables affecting fatigue performance include chemistry, microstructure, and texture, and of course, these are controlled during the make-up and processing of titanium alloys. In addition to the material factors, fatigue performance is determined by the surface conditions of the material, environmental factors, and of course specimen geometry and test variables." p. 52
	==> can't just specify the material's chemical composition

Boehlert, C. - 'Fatigue and wear evaluation of Ti-Al-Nb alloys for biomedical applications'
	"the fatigue strength and lives of the as-processed alloys are comparable to that for Ti-6Al-4V(wt.%)." 
	"The wear resistance for the alloys was significantly greater than that for Ti-6Al-4V(wt.%)."

Boehlert, C. J.; Cowen, C. J.; Quast, J. P.; Akahori, T.; Niinomi, M. - 'Fatigue and wear evaluation of Ti-Al-Nb alloys for biomedical applications'
	Ti-15Al-33Nb(at.%) and Ti-21Al-29Nb(at.%)
		Tested at R=0.1 for maximum stresses between 75%-90% of the ultimate tensile strength
		"The wear resistance of the Ti-Al-Nb alloys was more than three times greater than that for Ti-6Al-4V." (p. 329)
		
	In particular, the specific alloy most widely used for implants is Ti-6Al-4V(wt.%) extra-low interstitial (ELI) because of its excellent biocompatibility and its combination of high specific strength, fracture toughness, fatigue and corrosion resistance, low density, ductility, and elastic modulus, oxidation resistance, and conventional processability. (p. 324)
	
	It is also noted that others have found some detrimental side effects due to the presence of Al ions, and thus Al alloy additions may be a concern for biomedical applications [28,29]. (p, 324)

Hosseini, Shabnam - 'Fatigue of Ti-6Al-4V'.pdf
	pp. 76-77
		Other biocompatible titaniums
	p. 78
		Ti-6Al-4V ELI and NiTi shape memory alloys (SMA) are the most commonly used Ti alloys in orthopedic applications because of their good combination of mechanical properties and corrosion resistance. 
	p. 79
		Table - various titanium alloys with properties
	p. 83
		Ti-6Al-4V is generally considered as a standard material when evaluating the fatigue resistance of new orthopedic titanium alloys. The mechanical response of Ti-6Al-4V alloy is, however, extremely sensitive to prior thermo-mechanical processing history, e.g., prior [beta] grain size, the ratio of primary à to transformed [beta], the à grain size and the à/[beta] morphologies, all impacting performance, particularly high-cycle fatigue lifetime (HCF).
	p. 85
		In addition to alpha grain size, the fatigue life of Ti-6Al-4V components is influenced by the amount of age hardening, oxygen content, and grain morphology [17]. High cycle fatigue tests performed on Ti-6Al-4V showed that by decreasing alpha grain size, fatigue properties of both smooth and notched (Kt=1.8) specimens, can be improved [18].
		
		Fig. 7 shows fatigue reduction percent for LCF and HCF for various tensile strength, but for constant stress concentration factor (Kt=3.6). According to this figure, the fatigue reduction percent decreases with increasing tensile strength. 	

Morrissey, Ryan - "Fatigue strength of Ti-6Al-4V at very long lives" [U/S tests] ==> need full reference
	http://www.sciencedirect.com/science/article/pii/S0142112305001799
	
	The objective of this research was to investigate the fatigue strength of Ti?6Al?4V using an ultrasonic fatigue system. Fatigue testing up to 10^9 cycles under fully reversed loading was performed to determine the ultra-high cycle fatigue behavior of Ti?6Al?4V. Endurance limit results were compared to similar data generated on conventional servohydraulic test systems and electromagnetic shaker systems to determine if there are any frequency effects. Fatigue specimens were tested with and without cooling air to determine the effects of increased specimen temperature caused by internal damping due to cycling at a very high frequency. An infrared camera was also used to record specimen temperatures at various load levels. Results indicate that the effects of frequency, including internal heating, on the very high cycle fatigue behavior of Ti?6Al?4V are negligible under fully reversed loading conditions.
	
Janecek, M. - 'The Very High Cycle Fatigue Behaviour of Ti-6Al-4V Alloy'
	20 kHz
	
	Fig. 2 (p. 498) shows SN run out at 10^9-10^10 cycles (electropolished). Runout ~440 MPa (64 ksi) (see p. 499)
	From the practical viewpoint N ÷ 10^8 may be set as the fatigue limit of this alloy. 
	On the other hand, the behaviour of the alloy may differ as a result of diferent heat treatment. A marked decrease in fatigue strength of titanium alloys above 10^7 cycles was observed in [21]. (p. 499)
	
	The Ti6Al4V alloy was used in this investigation. The chemical composition is declared by the supplier: Al (5.56.75 wt.%), V (3.54.5 wt.%), O (<0.2%), Fe (< 0.3 wt.%) and C (< 0.1%), H (< 0.015 wt.%) and N(< 0.05 wt.%). The beta transus of the alloy is 995C. The material was prepared by annealing at 980C for 1h followed by water quenching. Subsequently it was annealed at 800C for 1h followed by air cooling. Final aging was performed at 500C for 24h [11]. ==> STA?
	(See "Results and discussion" for more info, esp. the "best" microstructure best fatigue (ref. 14).)

Fatigue
	Fatigue notch sensitivity.
	
-------------------- Titanium --------------------
	- Standards & Specs ("Titanium; A Technical Guide", Appendix I, p. 349)
	- Machining
		- "Titanium; A Technical Guide", Appendix C, p. 265
	- Fatigue
		- "Titanium; A Technical Guide", pp. 177 - 178 (graphs)
			- Comparison to Ti-10V-2Fe-3Al forging (p. 183); Boyer ref. p. 232
		- "Atlas of Fatigue Curves" -  see bookmarked with postit notes
	- Heat treatment
		- "Titanium; A Technical Guide"
			- Duplex annealing (p. 32)
	- Eqivalent worldwide designations
		- http://www.aircraftmaterials.com/data/titanium/tital.html
		- check one of the ti trade assns.
	- FEA - recommend
		- Poisson's ratio
		- E (L) for plate
	- Neppiras, "Very high energy ultrasonics"
		- p. 149, "Not only the internal friction, but also the elastic modulus, is a function of the strain. Below the plastic region the modulus decreases in a regular manner with increase in strain." (not specifically referring to Ti)
	- Wuchinich
		- Sintered Ti -
			- Lower loss in unannealed state but drops to conventional 6-4 loss when annealed
			- Props closer to isotropic?
	- Appendix A (E for 1.5 dia rod)
		- Specify which tests were full-wave/half-wave tests.
		
	- List of worldwide Ti designations from non-commercial site
	
	- Increased wear resistance
		- "Med Applications of Ti & Its Alloys" -  p. 240 Ti-Nidium
		
	- Ti-7Al-4Mo
		- Show Q graph; state max strain for Q test
				
		  <li><a id="branson_ultrasonics5" title=""></a><span class="_author">Branson Ultrasonics</span>, (5) <span class="">"<a href="articles/Branson - 'Technolog TL-18, The Advantages of 7-4 over 6-4 Titanium for Ultrasonic Tooling'.pdf">Technolog TL-18, The Advantages of 7-4 over 6-4 Titanium for Ultrasonic Tooling</a>"</span> (pdf)</li>
		

Carpenter (http://cartech.ides.com/datasheet.aspx?I=101&TAB=DV_DS&E=269&SKEY=101.35.4356764%3A32538541-e77e-46b6-a40b-ec175a245a12&CULTURE=en-US&	) -
Using the rating system based on AISI B1112 steel, the machinability of Ti 6Al-4V is rated at 22% of B1112. In general, low cutting speeds, heavy feed rates and copious amounts of cutting fluid are recommended. Also, because of the strong tendency of titanium to gall and smear, feeding should never be stopped while the tool and work are in moving contact. Non-chlorinated cutting fluids should be used to eliminate the possibility of chloride contamination. It should be noted that titanium chips are highly combustible and appropriate safety precautions are necessary.

Cross-rolling:
	- http://www.eng-tips.com/viewthread.cfm?qid=141900
	
Ti materials with low E (tune short)
	- "Titanium-Based Biomaterials for Preventing Stress Shielding between Implant Devices and Bone" (http://www.hindawi.com/journals/ijbm/2011/836587/)
		- "The lowest value of Young?s modulus reported for the polycrystal ?-type titanium alloy, Ti-35Nb-4Sn [5], or Ti-24Nb-4Zr-7.9Sn [6], subjected to severe cold working, is around 40?GPa."
		- "The authors have also developed a ?-type titanium alloy, Ti-29Nb-13Ta-4.6Zr, referred to as TNTZ, that is composed of toxicity- and allergy-free elements and that has a low Young?s modulus. Young?s modulus of TNTZ subjected to solution treatment and measured by a resonance method has been found to be around 60?GPa [7]. This value is lowered to around 55?GPa by severe working such as severe cold rolling and cold swaging [8]."

Accepted biomedical  alloys:
	Carpenter (http://www.cartech.com/techarticles.aspx?id=1570) - September 2003
		- Ti-6Al-4V, Ti-6Al-4V ELI, Ti 6Al-7Nb and Ti-CP (commercially pure) grades 1, 2, 3 and 4

	Azom (http://www.azom.com/article.aspx?ArticleID=1794#_Surgical_Instruments)
	5/29/2015 - submitted via online form -
		Your site (http://www.azom.com/article.aspx?ArticleID=1794) lists various titaniums that are suitable for medical applications. Is this a complete list? If not, do you have a complete list or where can I find such a list. (If it matters, I'm particularly interested in titanium for surgical devices.) Thanks.
	
	Titanium Information Group -
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		PH: 44 (1709) 722 463 
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