Posted: 4/2/2006 1:59:38 PM EDT
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Go here: Ferium S53 You come here asking questions about this stuff? I hope you are not building aircraft or something along those lines. Geesh. ETA: Why don't you call the manufacturer? They might know, or do you work for them? |
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I think that Ashcroft and Mermin (Solid State Physics) would give you a decent explanation as well. Bassically, you can have a slip fault along any of the preferential crystal directions, so if you slip a single plane over, the next plane can rebond, in this manner a linear dislocation can move through the material. Any type of discontinuity in the crystal, be it an ampty lattice site, an inerstical attom, an impurity attom etc, causes the energy required for the slip to be greater, thus the material is stronger. Sorry not a meturlagist, just a lowly Physicist. (Which means I need drawing to explain anything well) |
As long the dislocation movement is hindered, why does it matter if it was done by substitutional or interstitial atoms? That question is more academic than practical in my mind (please correct me if I'm wrong). How long was the material temepered and how many percent of lath martensite are still present? The majority of the martensitic phase should be transformed to the globular form after tempering h If I remember it correctly, the strengthening mechanism gained by the presence of lath martensite is primarily due to extensive lattice strain and cleavage. This multiplies the presence of dislocations, which will hinder each other's movent (due to multiplications and pile ups). The boundaries from the fine grained structure would make it harder for the dislocations to move because of the directional changes from grain to grain (I'm sure you already know that). You think too much |
THey precipitate just like any other form of carbides, through nucleation and diffusion process, don't they? The main ingredient for this transformation kinetic is low diffusion rate and high nucleation rate of the particles. From the alloy's TTT diagram, would it be possible to figure out the heat treating schedule to see how the second phases precipitate out of the matrix? As far as bonding and energy are concerned, fine grains do not only hinder the movement of dislocations due to drastic changes in prefered slip directions from grain to grain. The grain boundary is also super rich with dislocations. Dislocation densities along grain boundaries are significantly higer than that found at the center of the grain. This causes dislocation multiplication and pile ups to occur, causing dislocation movements to stop due to entanglements. Dislocations along grain boundaries must also "rearrange" themselves for metal to deform and the more grain boundaries you have, the more dislocations there are, the harder this process to take place, causing the fine grained material to be stronger. Good for applications in ambient / slightly elevated temperature, but in elevated temperature, fine grain materials tend to do poorly. HIgh dislocation densities also means higher stored energy, and with the introduction of additional energy from elevated temperature, grain boundaries starting to slide along each other, easing the deformation process. That's why I understand that metals for turbine parts are directionally cooled to produce what is essentially a single grained material. Is the above discussion what you're looking for? OR did I just waste your time? |
Precipitates are clusters of atoms bonded together. They are not substitutional or interstitial, but the precipitate's carbon atoms are interstitial atoms. Can you analyze the precipitate and the matrix composition using XRD / EDS? |