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Message: <blockquote data-quote="buzzard" data-source="post: 518262" data-attributes="member: 3003">OK, being a real metallurgist [I can exhibit my big fat unused PhD n Materials Science for those who wish to ooh and aah], I figure I better set some of the claims made here straight. The initial claim about why Japanese swords were layered was correct. It was an issue of poor steel with lots of impurities. These are known as inclusions in the steel business. They generally consist of non metallic particles trapped in the metal. Given that they are brittle, hammering will either break them out of the metal, or render them into a fine enough size to not weaken the structure (the important aspect of a fault in a material is the crack size, and if we assume that the inclusion is poorly bonded, it will act as a crack). So the Japanese sword smiths hammered the heck out of the blades to compensate for lousy steel. Now it is possible that this could have introduced some nice cold work into the blades, but given the martensitic quench which was uniformly followed, any internal cold work would have been eliminated (which is probably for the best since it would have made things too hard where they didn't need to be).As for alloying, well that is rubbish. There was no titanium powder available in fuedal Japan. In fact processing titanium ore into a pure metal is a relatively modern process, which was discovered in the 18th  or 19th century (I'd have to check). You have to react thet titanium oxide with flourine gas. Needless to say Japanese smiths didn't tend to have cylinders of flourine sitting around. Though titanium is not a particularly interesting things to add to steel for strength anyway in spite of it's wonderful marketing these days. More useful things would be manganese, molybdenum, or vanadium. None of these are common, and they certainly weren't available to early smiths. Alloying did occur by happenstance in many early steels, but that was due to impurities in the ore. Then there's the making the 'latticework of carbon', umm well this doesn't make much of a realistic picture. The smiths did not practice metallography, and probably wouldn't etch the metal even if they did micro-polish it. Thus, the latticework wouldn't be revealed. The creation of different carbide precipitate structures does happen, but they would be a by product of what they did to get the properties they found. The smiths probably didn't know the metal had carbon in it, or at the least didn't know about carbide precipitates. In any case the latticework is fairly irrelevant. Any regular dispersal of the carbide precipitates will be useful, pretty pattern or no. What you are essentially making is a metal matrix composite where the carbides act as the stiffener. Though one final point on the finishing of the blades. You will do the clay on one side quench to create the martensitic edge. However you will likely heat it up again somewhat (not as hot) to temper that martensite to cut how brittle it is. The martensitic transformation leaves a lot of stress at the atomic level (the transition is a product of the shift in atomic stacking type, anybody is is dreadfully bored can ask me for more details) and heating things up a bit allows the atoms to re-arrange themselves to alleviate some of this without reducing the hardness appreciably. A good smith would know of this (and by any measure those who made katanas were good smiths). Now, as for buying a sword, I'm no expert. However it would seem to me that what you intend to use if for should be the driving matter. If you want it for display, well make sure it looks good. Don't worry about the metal. Almost all steel made these days is of good quality (though it seems that most steel I have seen out of the PRC sucks, but that may be my bad luck). If you intend to use it for hacking people up, go see a shrink. If you live somewhere nasty enough that a sword might be wise to keep your butt in once piece, buy a gun, they work much better(and are generally made of some nice alloys). I suppose there could be some pride issue involved in having a folded blade, but in practical terms they would not be better then a carefully made modern example made with good steel. Dr. buzzardB.S., M.S., Ph.D. Materials Science</blockquote>

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