Titanium Weapons

[Jon_Snow]

General Geoff, TiN coatings have been done, see below:

http://www.midwayusa.com/viewProduct/default.aspx?productNumber=446331

Other than the 'bling' factor , they do supposedly resist wear quite well. The problem comes from the mating surface. I have no first hand experience with this but I've heard that TiN coated bolts tend to lead to worn out locking lugs.

 

[fletcher]

all three have approximately the same strength to weight ratio.

Maybe if compared to a different class of materials (polymers, ceramics, etc.) one could use that comparison.

For a given alloy and heat treat condition, choose typical yield/tensile strength values and divide them by the density for comparison of "strength-to-weight" (specific strength). You will find that they differ enough to be significant. It's also not just about strength to weight, but strength to bulk. Sure, maybe you could get a 10lb piece of aluminum to hold a somewhat comparable amount as a 10lb piece of steel, but the aluminum will be much larger. For aerospace structure, where weight is a concern, aluminum and titanium are almost exclusively chosen over steel for this reason. Maybe it's just knowing how a substantial difference is interpreted from an engineering/design standpoint. Here is a good illustration from the University of Cambridge department of engineering:




The ultra high strength steels in the 400-500 ksi UTS range have extremely limited use, as materials with strengths that high sacrifice things such as toughness and ductility, which are extremely important in applications such as firearms. High strength steels that are useful and versatile from an engineering standpoint will typically be lower than 300ksi. The absolute highest strength steels will be pure martensite, which will result in a high specific strength (for a steel), but as a result is extremely brittle.

 

[Remo223]

fletcher, your graphs prove my point.

equivalent strength to weight ratios will occur along a straight line. Superimpose those two charts and then draw a forty five degree line from origin to the uppermost right corner. any point along that 45 degree line will be equal strength to weight ratios. All three, titanium, alloy steel, and aluminum will pretty darn closely have their centroids ON THAT LINE.

The only one that is off is magnesium. magnesium does have a superior strength to weight ratio(on average) compared to the big three.

btw, prestressing strands in prestressed concrete have a rupture strength of roughly 300ksi. They are steel. And they are VERY USEFUL AND VERSATILE structural engineering steels.

 

[fletcher]

A more appropriate comparison is straight horizontal lines for a given strength. For example, at 200 MPa, follow the line across. This will indicate how dense the alloys are in that area, and consequently how much it will take to do the job, for a desired strength. A vertical line will show much the same thing - how much strength you can get for the same density.

Just because the alloy used for strands in concrete is useful does not mean it is very versatile. Odds are you won't find that same alloy in many other applications, just like you probably wouldn't find a 1095 spring steel being used much outside springs or maybe knives. Many alloys are developed for niche applications such as that. Alloys like 15-5, 4340, 304, 1018, etc. would be considered much more versatile. Even magnesium, which you claim has no long term use, is flying long-term on nearly every aircraft you see. It has corrosion protective treatments like Keronite or Dow 7, and has been alloyed to not burn.

I'll give another comparison between 15-5 PH steel and 7075-T6 aluminum. Let's say a 1 foot long rod is required to hold up 10,000 lb, and both will be loaded right at their respective yield strengths. For this example, using the data below, the aluminum can carry the same load at at 15% less weight, albeit with a much larger cross-section (2.4 times that of steel). That's pretty significant.

15-5 PH
Density: .280 lb/in3
Yield Strength: 165 ksi

7075-T6
Density: .102 lb/in3
Yield Strength: 69 ksi

I'm not sure why you insist on trivializing the difference in specific strength between the metals.

 

[Strykervet]

Even 'aluminum' rifle actions like a Stolle Panda have a steel insert in the receiver that the barrel is screwed into and the bolt locks to.

There is no aluminum exposed to loading from firing.

'Alloy' 1911s still use a steel barrel.

IIRC the cylinder in 'Scandium' revolvers is steel.

Titanium and aluminum have fatigue life mechanisms not present in steel.

No, they make both. Probably due to recoil complaints. I have a scandium 340PD with a titanium cylinder. Works great. Very hot loads though will chip the titanium cylinder around the forcing cone. Only use factory loads in these unless you load soft practice rounds.

 

[Strykervet]

delete, copy

 

[Strykervet]

S&W does make a scandium frame 1911. I think they make another auto too, but cannot be certain.

 

[Remo223]

A more appropriate comparison is straight horizontal lines for a given strength. For example, at 200 MPa, follow the line across. This will indicate how dense the alloys are in that area, and consequently how much it will take to do the job, for a desired strength. A vertical line will show much the same thing - how much strength you can get for the same density.

Just because the alloy used for strands in concrete is useful does not mean it is very versatile. Odds are you won't find that same alloy in many other applications, just like you probably wouldn't find a 1095 spring steel being used much outside springs or maybe knives. Many alloys are developed for niche applications such as that. Alloys like 15-5, 4340, 304, 1018, etc. would be considered much more versatile. Even magnesium, which you claim has no long term use, is flying long-term on nearly every aircraft you see. It has corrosion protective treatments like Keronite or Dow 7, and has been alloyed to not burn.

I'll give another comparison between 15-5 PH steel and 7075-T6 aluminum. Let's say a 1 foot long rod is required to hold up 10,000 lb, and both will be loaded right at their respective yield strengths. For this example, using the data below, the aluminum can carry the same load at at 15% less weight, albeit with a much larger cross-section (2.4 times that of steel). That's pretty significant.

15-5 PH
Density: .280 lb/in3
Yield Strength: 165 ksi

7075-T6
Density: .102 lb/in3
Yield Strength: 69 ksi

I'm not sure why you insist on trivializing the difference in specific strength between the metals.

You are rambling fletch. The fact remains, I am correct. regardless whether you think there is a more "appropriate" comparison or not.

 

[Ole Humpback]

Remo,

You're only correct if you neglect the Modulus of Elasticity & Moment of Inertia. Ever look at the weight difference between wheels on a car if the same wheel is steel, aluminum, or mag? They're within about 5-7lbs of each other. If were talking a street car, that's meaningless fine and well but not worth the cost. If were talking a racecar, that's the difference between winning a loosing.

Steel gives you cheapest, smallest, and best packaged wheel for any size imaginable. Steel by far has the best strength to weight ratio because you don't need to add bulk to make up for a low Modulus of elasticity and you can have a relatively low Moment of Inertia with high load capacity.

Aluminum is the happy medium. You gain bulk (about 10% over steel) and drop some weight (about 15% over steel) for twice the price per pound of material. Aluminum also has to be used in wheels over about 16" for street use because any smaller & you start having issues with wheel deformation under turning.

Mag is a pain in the rear and justifiable only for large street wheels or race use where large wheel & tire packages are needed. Ever see a Mag wheel in person? I have. They are MASSIVE in relation to Aluminum wheels that weigh only a pound or two more than they do of the same diameter. Mag is extremely elastic and deforms readily which requires a wheel with a very large Moment of Inertia to overcome the very weak modulus.

Strength to weight ratio is VERY subjective. If were talking Ultimate tensile strength to weight, Titanium is the strongest of all metals. If were talking Ultimate compression to weight, Iron is the strongest metal. If were talking most stiffness to weight, Mag is the strongest. If were talking Yeild to weight, its Aluminum. If were talking least elasticity per weight, its Steel. If were talking best overall design characteristics, its A36 steel. The list goes on and on.

I'm not talking out my rear. Designed and machined a ton of parts for racecars for a while now. If there's one thing I've learned, its that often times a thin sheet of steel is far more useful and than moderately thick sheet of aluminum. Trading strength for bulk ends up adding weight in the end.

 

[fletcher]

You are rambling fletch. The fact remains, I am correct. regardless whether you think there is a more "appropriate" comparison or not.

You're really not, but believe what you like. For strength to weight, this is how we in aerospace assess the properties, and this is consistent with the views of my fellow metallurgists. Like Ole Humpback said, if properties like stiffness/modulus are important, those are taken into account. For straight up weight, aluminum is generally selected and the reduction in modulus is just accounted for in design. Design can account for a lot of things if you're really set on one or two key properties.

These types of alloys only have "comparable" specific strengths if you're looking at them very loosely. If you were actually designing a part where weight is a concern, you'd quickly learn that they are in fact quite distinct, with even more differences if you take into account additional material behaviors. The proof has been posted, and it's not really worth it to try and continue on this matter and further derail the thread.