Titanium alloys

[zerogara]

http://www.unb.ca/web/P&P_Centre/engcomp/engcomp.htm
http://www.key-to-metals.com/Article20.htm
http://www.ul.ie/~mst/jeremy/abstract/elements_ac.html

Here are 3 informative short articles I found on the subject, and after reading some about Ti, and after someone has mentioned this as a possibile material to be used in boat construction by improving strength over any other composite, I thought the discussion might be best suited for the materials section.

The fact that a hull of titanium hasn't been created yet that doesn't mean one can not! There was a first in every material used.

So why, or why not, may help us inderstand why do we choose the materials we do use!

[Windvang]

You may be right abouth environmental issues, I have no clue abouth that.
Wood is probably best for that. Metals usually need huge amounts of energy to make.

Pannel weight for a Volvo 70 is 7.4 kg./m2, unless you can lower density that would be titanium sandwich with +/- 0.4 mm skins. I have no doubt you can make that in a lab environment, I will have deep respect for you if you can build a hull out of that.

Titanium is great for some parts, and even for hulls too, just heavier. Metal knowledge will advance but so will composite's.

I have seen 35 year old GRP boats without a single sign of fatigue I have also seen totally tired aluminium boats of 5 years old, no sign why composite boats shouldn't last.

[zerogara]

by an other member on an other thread:
D'ARTOIS says:

The problems with titanium generally are enclosed in its limited availability, its costprice and the toughnes of the metal in the forming and machining process.

Welding is no issue, any professional welder that can weld stainless steel perfectly can also weld titanium.

The present main supply sources for the military type of titanium alloys are Russia and China. Russia, back in the early '90's had such large surplusses of Titanium that prices sank to DM 17,50 per kg in sheet and profile. Thousands of tons have been disposed of meanwhile just like their strategic stocks of aluminium and copper, but that is history now.

The two main alloys, Ti-6Al-4V (IMI318) and Ti-5Mo-5V-2,5Al are commonly used in the process-aerospace industry and for specila applications.

Both are alpha-beta alloys.

Some properties of Ti-6Al-4V are: (AMS 4928F)

Ultimate strength (psi): 160000
Yield strength: 145000
Charpy V-notch impact @ Room temp (ft-lbs) 10500
Viscosity of breaking MPa mm 1/2 : 1160-1420
Shearing strength (psi): 93600
Density (lbs/cu in) : 0.16
Melting point (F) 3200

It is not the most ideal type for sheets, Ti-5Mo-5V has better specs/properties is quite more elastic and is over the whole range superior;

The thermal conductivity of these two titanium alloys is low: 3.73 Stu sq.ft./F/ft

During the testprocesses with several alloys, we learned that it is possible to weld AlMg4,5 direct to Ti-6Al-4V and that testing the strength of the weld, the aluminium broke off after the weld, not at the weldseam.

Forming without pre-heating is very difficult. A 100 tns press could just bend a 3mm sheet: the form memory is incredible. If not preheated small cracks on the surface will occur. At proper preheating by way of electrical oven, surface cracking will not happen.

As to corrosion: The corrosion resistance is second to none: 1/1000mm in 1250 years in polluted seawater;

There are several surface treatments possible : electrolytic polishing and diamond coating under absolute vacuum to give it the highest form of abrasion resistance are the most common. Electrolytic polishing will give a surface that is similar to high polished stainless steel; with the only diffrenec that this look will remain while stainless steel will dull and if not repolished regularly it will rust in a seawater environment.

The reason for the high costs of Titanium is not the natural availability but the very high volumes of electricity required in the manufacturing process.
Just like aluminium but in a tenfold.

It was the only building material available for the construction of the A12 and the SR-71 (thanks for the correction usa2) because of the high temperatures that occur at flying at high mach numbers. Aluminium will melt and could therfore not be used.

As to weight: The panelweight of a Titanium panel will be around 13,5 kgs per sq. meter (w/o reinforcements) A bare hull with reinforcements for a VOR 70
would have an estimated weight of 7000 kgs.

might be the limiting factor.

I mean from what I understand most of the Russian Migs were made of titanium - light strong flexible and not subject to corrosion.

But - how it rates on the nobility scale (compared to say marine grade 5000 & 6000 series alluminium alloys) in as far as galvanic corrosion (electrolysis in a marine environment) I don't know? (Its valence figure?)

Anyway - I do know a guy who manufactures about the best saltwater fly reel on earth - out of a special aluminium alloy - and he uses reel feet (for attaching the reel to the rod) made from titanium. (I think he steals it off Russian Migs!)

I would think if it were affordable - he'd make the whole reel out of titanium....

From what little I know - I'm thinking cost is probably the prohibitive factor.

Others may well know a lot more than me.

Cheers!

[Windvang]

Thank you D'Artois for that information. DM 17.5 is good vallue for money! Any clue of the price nowadays?

[D'ARTOIS]

I must admit that I do not know the real costprice at present per kg, but it will be in the area of Euro 35,-- per kg based on the price I have paid some years ago.
So to make a reel for a fly fishing rod will ( I shall weigh mine now: 160 grs, made out of teflon impregnated aluminium and had cost me 100 Euro if I remember well) take not much for the material but for the machining of the parts. If you apply diamond coating you give this reel an almost eternal life, because wear would not or hardly excist.

Basically, Windvangs remark that Ti is better used for a cruiser rather than a racer is indeed the most practical way to look at the subject. Although I wonder what the panelweight will be of a composite boat? And what the real costs are per sq. mtr.
Will it be noticeable cheaper than Ti? Also carbon comes in grades. Which grade is used in the VOR boat. Is someone able to give actual strength for weight example of a VOR composite panel?

Making a swift calculation I come up with a hullweight of approx 7000 kgs for a bare hull with reinforcments. Not counting the keelconstruction.

What is the weight of a bare VOR hull?

[D'ARTOIS]

Zerogara, that 17,50 DM happened to be in the period that Russia dumped its strategic stocks on the EU market. That was in 1996-1997. Then it was feasible to construct an entire hull from it. A costprice of 35 Euro per kg makes it less attractive. Your observation of going back to more metal-research and the environmental issue is more than true.

[Windvang]

Originally Posted by D'ARTOIS

I
Basically, Windvangs remark that Ti is better used for a cruiser rather than a racer is indeed the most practical way to look at the subject. Although I wonder what the panelweight will be of a composite boat? And what the real costs are per sq. mtr.
Will it be noticeable cheaper than Ti? Also carbon comes in grades. Which grade is used in the VOR boat. Is someone able to give actual strength for weight example of a VOR composite panel?

Making a swift calculation I come up with a hullweight of approx 7000 kgs for a bare hull with reinforcments. Not counting the keelconstruction.

What is the weight of a bare VOR hull?

I don't know the area's for a Volvo.
Pannelweights are:
Foreward of main bulkhead, below cwl : 11.3 Kg./m2
Rest below wl : 8.6 kg./m2
Topsides : 7.4 Kg./m2
Bulheads : 6.5 Kg/m2
Deck : 5.7 Kg/m2
Core nomex and PVC 30mm.
Skins : High Strength Carbon (lowest tensile strength, highest impact strenght)

For a high tech cruiser (Wally) pannel weights are 1.5 times that.
Material price for a 40' in carbon aprx EU 55.000

[zerogara]

It seems as you guys in the Netherlands are up to something.
What is this infactuation you have with metal boats anyway?

http://www.stork-aerospace.com/page.html?ch=DEF&id=1010

"On June 23th 2003, SP aerospace and the Dutch Royal Netherlands Air Force performed the first test flight in the world with a Metal Matrix Composite landing gear part."

Picture of "SEM (Scanning Elecron Microscopy) picture of TMC coupon fracture surface"
"Fracture and failure mode analysis of coupons. The SCS-6 fibers are clearly visible, as well as the fractured titanium matrix"

I'm still looking for titanium alloy fibers and cloth/mesh that one can incorporate as a laminate within a traditional composite, but I think the advantages would be in a thin (almost like electroplating a hull) film on the hull.

[D'ARTOIS]

Zerogara, I am playing for years with this idea - and therefore I am completely with you. The point is that the tooling for the dies might be very, very, costly.
But if you can overcome that, indeed it could be used as a reinforcement within a composite structure. And from there, you will find many applications.

[D'ARTOIS]

He Zerogara, that post is brilliant!!! Now there is a solution for the rams of the canters!!!!!

Don't you think so?

[zerogara]

Now I can go back and lay some E-Glass and polyester

Apart from high-tech just for trivial knowledge I'm short of old fashioned in sailing designs as a sailor. The idea of being gybed by some twister gust and have that bulb on the extreme of the opposite tack horrifies me.
I would though feel more confortable with the idea of twin radial fixed keels that ballast can be moved to or actually removed from. If you were to compress air on the leeward side you may get some of the effect of the canting keel with some added friction of the twin keels.

I haven't learned anywhere as much about Ti yet, but do you know whether you can use elctrolysis to transfer it into a shaped metal? If the mold metal will be selected as such that at some point it will release or be melted/scraped/ground off the plating, then we have a way to mold titanium foil (I don't think you can do the same to alloys).
I short of had my impression of Ti and Magnesium mixed up and thought it was Ti that corroded, and it seems as this is one of its most important qualities in the marine environment. I wonder if it's oxide is also toxic enough to minimize growth and therefore have a clean highly polished surface that needs no bottom coating.
And Ti propellers! Wow!

Maybe the future is not as boring as we are afraid it will be.

[D'ARTOIS]

You mean shaping by eletrolytic erosion, as is done by the making of tools. I am afraid that such a system would not work due to the enormeous resistance of Ti against all kinds of acids and gases. Actually no acids and gases can influence i to corrode drastically and in ashort time. Ti metal is almost inert to anything.

In the run of the next days I will check my files if I can find more surprises.

In Germany there is a laboratorium where they make all sorts of crazy things, from valve springs for the F1 Williams and Ferrari (brotherly next to each other)
till the smaal bits dentists use for implantates.

[zerogara]

One bad thing with carbon (kevlar, glass as well) is that when its glue fails all you have is a silky soft cloth. Many people build with composites for decades but are never around when fatigue has worked its miracle to reach the material's deadline!

And out of all the places in a sailboat that is subject to fatigue carbon has found itself in spars. If it is made stiff enough not to deflect it is useless, if it is allowed to deflect it will eventually fail.

From what I read about Ti you can take a thin flat plate and put it in a press to shape it and once you realease the pressure it wants to become the same flat panel. Perfect spring material.

Aren't all F1 engines now running pneumatic valve springs, to keep up with the speed?

You guys are way ahead of me in ti technology.

I seem to recall a few years back - fly rod builders incorporated ti into high modulous graphite fly rod scrim fly rods, but it was reputedly in small particulate form - mixed in the resin?

The idea I berlieve was that Ti's S to F (Strain To Failure) ratio was better than some of the other materials in use...

A better (faster) "Return to battery" (straighten out after being bent) was the property all fly rod manufacturers seek to achieve...

Supposedly, the faster / harder a fly rod straightens out, after the caster has induced a bend in it - the farther and faster it will thriow a fly line (and hence the fly) out into the water to catch fish..

Course the very property that makes a fly rod a fantastic casting instrment - works against it as a fish landing instrument...and the more "Improvements" were made to fly rods in the casting department - the less able they were to land big fish without spectactular failures...

I think it's testament to the few numbers of fish fly fishers actually catch - that fly rods were developed to the point - they werent much good at landing fish...but I digress.

So - titanium - seems to have been incorporated into the resin part of the grahite composites, by the leading US fly rod manufacturers.

What you take from that I don't know - but figured itmight be worth mentioning!

Whether Ti could be interwoven into a composite Carbon - Graphite / Ti scrim material cloth for later application of resin, I don't know...

One of the biggest "problems" with these new space age scrim materials - seems to be getting the resins to actually be able to "bond" successfully to the scrim material..graphite being a particularly slippery little sucker!

I always wondered, how a woven (or fused) GSP gel Spun Polyethylene Scrim cloth material, bainded with cyanoaccryllate glues would hold up?

In some tests I did on GSP fishing lines (which are notoriously difficult to tie knots in due to their slippery nature)... cyanoaccrylate glues seem to hold up particularly well on preventing knots slipping, eventually breaking down tho (after 12 months or more), in the salt water environment.

Maybe theres a idea in there somewhere, for a new lightweight strong composite (GSP & cyanoacrylate) for comosite panels / or yacht masts etc - i don't know - I am certainly no materials engineer - but hell can I break fly rods - destruction testing on big fish, is my specialty!

Cheers!