Aluminum, even if this cryo-milling is as good as you say, makes for lousy armor. I'm going to have to look this process up. OK, I looked it up. The Cryomilling process is a way of producing metal powders for Powder Metallurgy products. The benefits of the process mostly come about from the fact that extremely small grain sizes are obtained. The addition of the nitrides into the strutcure actually is mostly to stabilize the small grain sizes. This is necessary during the process in which the powder is made into a part. If people are bored enough, I could explain why this process, in a simmilar mechanism to amorphous metals, produces strong material, However, I will refrain. Just take it from me that the benefits come about for very like reasons. However aluminum simply has too low a melting point to be resistant to a whole bunch of destructive forces. Also strength isn't everything when it comes to armor. Simply having a good amount of mass in the way of a solid penetrator is helpful. This is part of the justification for the DU armor. One thing to keep in mind when looking at this process as well as amorphous steel, is that the parts which can be made are relatively small in cross section. Given the fact that armor has gone the composite route these days, this might not be a problem. However, the idea that a big slab of cryomilled aluminum will be the future of tank armor is most likely fantasy. buzzard

Thanks for the input. Although I also am not anticipating entire hulls made of the stuff, this is basically (the cryomilling process, amongst others) the infancy of engineered lattice materials: designing alloys and materials to have molecular patterns in exactly the place you want the elements to be (like I said, the infancy of it, not the matured processes of almost-replicated-like materials where we build a structure, molecule by specific molecule, in the form we wish.) The possibility exists that, as we further such metallurgical sciences, we could develop the super alloys out of aluminum, yet acquire higher melting points when combined with other elements (hyrdogen mixed with oxygen will burn violently, yet a hydrogen-hyrdogen-oxgen molecule, water, can extinguish fire) It is safely feasible then that our super alloys could well be better-organized-and-aligned molecular matrices of known elements instead of some as-yet-unknown elements to be added to the Periodic Table years from now. Like I said, this cryomilling is in its infancy. I am not implying it WILL allow us a 30 ton tank with 70 ton protection. But it will ideally lead us closely to materials that will (just as the carbon nanotube/fullerene compounds are still in their infancy.) Look how long it took us, from the early days of the Iron Age, to make the strongest steel alloys we have today. Better understandings of how alloys bond and combine at smaller levels (near molecular) will help us better understand how to fabricate/engineer alloy lattices from the ground up (such as the expirements being done in labs with the latest and most powerful atomic microscopes and tools. If IBM can "build" their logo only several atoms in size, certainly this could be comparable to the early expirements with electricity or sound recording. Projects in their infancy now will afford us the future super materials later. That's what I'm trying to hit on in this thread.).

I'm probably betraying my ignorance here, but if the objective is (relatively) lightweight armor with high heat/fracture resistance, what about bi-or-multiphase carbon composites? Boron-nitride based structures like this have been known since the failed attempts to create the "Zip" boron-based jet fuels in the late 1950's (Callery Chemical was the main operator there, if memory serves), and led directly to the composite structures of modern aircraft, which use boron/graphite comps. I know these materials are used in secondary armor applications (such as the new Battelle-developed armor kits for our light vehicles in Iraq), but what about their future application to heavy armored vehicles?.

The problem with carbon fiber composites is that they have lousy impact resistance. The fiber wonderful in giving stiffness, but once you get past the yield strength, they do not deform, they crack like an eggshell. Deformation is what is required to absorb energy. Kevlar is appreciably different in that it deforms, which is why it is used in body armor. The latest and greatest (or at least it was) is Spectra 2000 which gives you good stiffness, but also deforms before failing. This makes for really nice body armor. However it is supposed to be quite difficult in that many matrix materials won't bond with it and those that do are quite noxious. Composites will likely remains central to future armor. The ability to mix and match properties in layers is very valuable. The strengths of weakenesses of different materials can be balanced to lead to an optimal solution. Trying to do this with one material is a bad bet. To address Dogtag's talk about future alloys solving problems, I can say that a lot of it simply isn't possible. It comes down to the nature of the inter-atomic bonds in question. There are three primary kinds of bonds found in solids. A) Ionic- fairly weak and brittle, think table salt. B)Metallic- pretty strong and pretty ductile, though the ductility can depend on the atomic stacking. C)Covalent- most commonly seen in ceramics. These bond types are listed in increasing strength. When we talk about amorphous steels or the cryo-milled alumnium, we are talking about pretty impressive materials. However they still have the inherent limitation of the metallic bond. What makes the materials impressive is that they are getting to pratical strengths which are very close to the theoretical strength of the metallic bond. This is a big deal compared to conventional materials. However this strength difference has no effect on melting point. Also, you really can't add things to an allow to increase the melting point. That only works in the case of forming an inter-mettalic compound (which ends up with a covalent bond, but is brittle like titanium aluminide). In general no alloy will have a melting point as high as the primary component. This is a fundamental thermodynamic effects. It's why salt works to clear your driveway. Thus looking at melting points (rough from my head) Aluminum alloys: 660 C Steel Alloys 1500 C Ceramics (alumina)2000 C If I'm going to make armor to resist shaped charges aluminum won't be on my selection list. I rather think a composite sandwich with a ceramic in it sounds much better. Now maybe cryo-milled aluminum might be worth considering for a portion of the composite, but I suspect that the amorphous steel would be stronger. So I'd go with that instead. buzzard

Thanks for all the input, buzzard. Down on the armor thread (best IFV), I was just recently suggesting more Chobham-type armors (layers of differing density/strength materials) for IFVs. But the problem there is that very few IFVs currently have anything more than 2inches of armor plating (even on the forward arc), so using layered systems has difficulties. But since we would be opting, for IFVs, 360 degree protection from small arms fire, machine guns, and light-caliber cannon fire (no IFV ever built will be able to fully withstand RPG rounds from just its base armor), we could create scaled-up versions (but adding metals) of ballistic armors as used for security vehicles and civilian-market bulletproof cars, which today can withstand even 7.62mm AP rounds (but not all IFVs, many of which are composed of some form/alloy of aluminum armor, can.) Certainly, we could tailor 40-50mm of an armor "panel" to be composed of various materials to offer greater capabilities than just a single element (metal) hull (like having an all-aluminum or all-steel hull.) The greatest weakness in using aluminum it that it burns when temperatures get above certain levels (like would be experienced when the vehicle gets hit by incendiary ammo and its own ammunition starts to cook off.) When the USS Stark (Perry-class frigate) caught an Exocet off the coast of Iraq back in 1987, it was found that components of the aluminum hull actually burned, not just melted, at the extreme temperatures of the fire. IFVs are no different: if they get hot enough from impacts, they'd just as soon burn rather than just melt (NASA uses aluminum compounds in its shuttle SRBs.) Personally, I think aluminum is the wrong material for the armor job, but in efforts to save weight (and money), sacrifices in crew safety and survivability will be made if it means the vehicle can be made lighter and cheaper (remember: the people designing and procuring military vehicles are NOT the ones who will be depending on them in a war environment.) I also mentioned that Apache helicopters use a ballistic nylon/boron carbide/ Kevlar sandwich for crew/pit protection in several places. And the A-10's pit "tub" is composed of titanium capable of (in tests) absorbing 23mm AP and 37mm HE hits The Army's FCS program suggests using titanium alloys in some variants, but titanium isn't among the low-cost metals. Years ago, the US expiremented with layers of fused silica glass between metals for a concept armor: the idea was that the glass would melt to absorb the shaped charge of a HEAT round. It is suggested Chobham-type armors feature some form of "sacrificial" material in one of its layers as well (an ablative material which disperses the energy by melting and boiling/vaporizing off.) IFVs just don't have the room on smaller-than-MBT hulls to support massive armors (>3inches thick), so innovative and novels ideas (like the UK's developments in electric armor...which will only be mostly effective against HEAT charges which use copper liners. All fine and dandy until more people realize the superior performance of tungsten and tantalum liners for their shaped charges)... so innovative and novel ideas will be needed to give IFVs worthwhile protection. I proposed a face-hardened steel armor plate (stronger at the outside surface than typical steel armor, yet "softer" at the backside), backed by a structural aluminum (if we must continue to use aluminum) composed of a cryo-milled material (double-strength?), and maybe some titanium/ceramic metal matrix material that could absorb heat away from the aluminum material, with a Kevlar anti-spall liner lining the inside of the vehicle. For crew safety, we need to remember to keep toxic elements to a minimum: the vehicle can get hit and still fight. But if materials in the armor start vaporizing away and get into the crews' areas, they could be sucking down hazardous vapor which could kill them over a longer, more debilitating method that an instant death in the vehicle. Again, sandwich armor is the future of AFV protection. No one "wonder element", however forged, milled, or fabricated, will provide overall exceptional protection levels from battlefield threats. Adding a few additional strap-on armor kits, as needed pertaining to the threat environment, is ideal for short-term solutions. But a hull/suspension/chassis designed to function ideally at a 25 ton weight will have a shorter operational lifespan (greater wear) if it suddenly has to always carry around an extra 7 tons of applique armor throughout the remainder of its life. At that point, design a heavier IFV. There is an article in the October issue of National Defense magazine (available at NDIA.org), on page 23, about research in cryo-milled materials being performed by the Carderock Division of the Naval Surface Warfare Center (in MD.) The project manager is one Rodney Peterson. Buzzard, with your obvious credentials/knowledge, you

I definitely think you're on the right track here. However, on thing most people don't know is that the burning problem in Aluminum can also be the case in Titanium. The fact that the material is do expensive has meant that it hasn't been used much in armor, but I suspect this liability would be a good reason to consider other materials. Aluminum and Titanium are chemically simmilar in that they both are very reactive, but have tightly adhering surface oxide layers which prevent further reaction. However at high temperatures diffusion through these oxide layers can get fast enough that either burning or powdering can occur. Titanium is much more resistant because of various properties, but the weakness is still there. Though as for me contacting the individual in question, while I do know a pretty good amount about the field of materials, I have no expertise in armor per se, and I don't even work in the field any more. buzzard

And if it seems foolish to build AFVs out of aluminum armor... Remember that, even thousands of years AFTER man dicovered fire, he was building ships out of wood for centuries. .

side note about fullerines. seems a research type has discovered that at least some buckeyballs seem to have rather serious effects on nerve tissue. he was looking at the effects of oil with buckyballs escaping into the marine environment and found problems with his little ecology. trout and crayfish so far have been the worst affected and he was going to be looking into mammals next.

Supposedly, asbestos was a fire-resistant wonder material as well...until we learned it causes severe lung cancer. And DU penetrators for tank ammo were supposed to be the perfect weapon also...even though we know DU in micro-fine dust particulates absorbed into the body can manifest all kinds of health problems. There are any number of even common household products that will emit very noxious and hazardous gases if they are accidentally ignited (plastic fibers in carpeting and clothing, for example.) Even indoor air quality tests can indicate how much pollution we breathe in daily just in our own homes: the deteriorating foam filler in our pillows, mattresses, and furniture cushions can, depending how old they are, be toxic above certain levels. Many homes used lead paint for ages (which also causes brain defects), and many hot water pipes used lead solder. Older homes in the US used asbestos to insulate heating ducts, and this had led to serious environmental regulations when homes need the stuff removed, or are being torn down. Even if the wood in your home gets damp, some of the fungus and molds that can grow there have very fatal (in large enough doses) spores. Mother Nature is quite capable of slapping us around, to remind us once and for all who's REALLY in charge. Certainly, man-made chemicals can cause problems, too. But we've got nothing on Nature. Supposedly, excess aluminum particulates in brain tissue is suggested to accelerate Alzheimer's, but does that mean troops who fight in and maintain aluminum-hulled AFVs over a 10-year service career have a higher risk of Alzheimer's than troops who fight in and maintain steel-hulled AFVs? (the Stryker proponents would LOVE to prove that one!) .

"Supposedly, excess aluminum particulates in brain tissue is suggested to accelerate Alzheimer's, but does that mean troops who fight in and maintain aluminum-hulled AFVs over a 10-year service career have a higher risk of Alzheimer's than troops who fight in and maintain steel-hulled AFVs? (the Stryker proponents would LOVE to prove that one!)" Unless those troops make a habit of scratching the aluminum to make dust particles to breathe, no. Metals don't flake. The case where aluminum would be getting into their system would be an armor breach by something trying to kill them. Alzheimer's in another 40 years would be the least of their problems at that point. buzzard