Mechanical properties of steel 11: texture, dislocations, defects

Video in TIB AV-Portal: Mechanical properties of steel 11: texture, dislocations, defects

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Mechanical properties of steel 11: texture, dislocations, defects
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The eleventh in a series of lectures given by Professor Bruno de Cooman of the Graduate Institute of Ferrous Technology, POSTECH, South Korea. The video begins with continuing discussion of crystallographic texture, pole figures and the consequences of texture, followed by a new topic on dislocations and other defects in steels.
Keywords The Graduate Institute of Ferrous Technology (GIFT)
Optics Reference work Spant Steel Rolling (metalworking) Cartridge (firearms) Photographic processing Ship of the line Material Texturizing
Steel Steering Reference work Texturizing Finger protocol Sheet metal Roots-type supercharger Alcohol proof Commodore MAX Machine Plane (tool) Plane (tool) Sequin Ship of the line Single-cylinder engine Mode of transport Material Flatcar Kranbau
Typesetting Reference work Capital ship Nut (hardware) Cluster munition Scouting Texturizing Boiler (power generation) Fighter aircraft Angle of attack Roots-type supercharger Replenishment oiler Gentleman Plane (tool) Single-cylinder engine Internal combustion engine Material Firearm
Scouting Mixing (process engineering) Texturizing Scouting Sheet metal Alcohol proof Ship class McDonnell F-101 Voodoo Fiber Plane (tool) Ship of the line Material International Space Station Van
Typesetting Typesetting Flight Tool Mechanic Schubvektorsteuerung Schubvektorsteuerung Ford Transit Glaze (painting technique) Ammunition Game Volkswagen Golf Lawn mower Ship class Gentleman Screw Plane (tool) Forging Firearm International Space Station Photographic plate
Finger protocol Schneckengetriebe Textile Volkswagen Golf Tool Gentleman Forging Plane (tool) Ford Transit Ship of the line International Space Station
Typesetting Insect wing Pressure vessel Gemstone Schubvektorsteuerung Scouting Cut (gems) Scissors Mixing (process engineering) Pen Wire Angle of attack Roll forming Screw Ship class Tire balance Ground effect vehicle Slip (ceramics) Spare part Musical ensemble Forging Ship of the line K├╝mpeln Material Typesetting Ford Focus Steel Hot working Schubvektorsteuerung Slip (ceramics) Bridge (nautical) Weapon Finger protocol Ammunition Sizing Cartridge (firearms) Plane (tool) Gas turbine Musical ensemble Ship of the line Stock (firearms) Model building Strapping
talking about so when you well when you look at this like a piece of metal pieces steel writing consists of crystals the little grains that you see an optical microscope over or single crystals and and so if if you would be able to do this year come and identify the crystal structure you'll be able to see identified the orientation of the unit South has I'm not when I say that as far it sounds very generous you orientation of the Crystal how we don't know orientation doesn't mean anything if it's not which respect to reference frame right so so you have to the orientations you know what's your reference that obviously that's what would do when inferences if if are reference coordinate axis was exactly the same coordinate axis asked for this unit sell this grain would be not you know oriented in these perfectly aligned to its own access rights so but obviously what what is important is the orientation for visa-free the what we call the laboratory coordinate system its past and planned development and and coordinate axis that we define because it's you know it's an obvious 1 to choose for instance when you roll material has the summit to be you know you will choose according at a laboratory cornered access it all along the rolling direction transfers to the rolling direction perpendicular to the rolling direction right to this and so and so that's what we do we know we define the orientation of old are crystals in which respect to that laboratory the freeing up as you will coordinate system and that it would would if we do this we we find that some steals when you look at the orientation of the crystals a know order randomly oriented and they don't have any particular of preferred orientation other cases which happens very often but when you deformed material heavily that is that you see that the unit sells line not maybe not very precisely but you know there is a preferred orientation right and this this would call texture and it was because of a big impact on the mechanical properties this this this texture it's too but I just want to say so and so the other methods to describe tests which are methods which which led to you to visually precent this texture yes and no that that's what I want to talk about it 1 of
the things you can do now it's use what we say of Asturias graphic projection writers would steer graft rejection relatively simple concept so I am just just imagine here that is gray it she'd hear gray sheet this is a is a piece of rolled steel has that I orient with the ruling direction in this direction the transverse direction in that direction so it's it's flat it's lying flat on only the surface and then the normal direction is my 3rd axis and then that I imagine it will be plane Nixonian but the sphere around this piece of metal right here and now I focused on a small grain a single grain inside this sheet of material used in the study said this is disagreeing this great thing here that's disgrace and I've chosen for as an example that this crane has 80 1 1 1 axis 1 1 1 axis perpendicular To be normal direction right and so what I do In it and what we call a figure which is a a of the representation of orientation before this little grade this little crystal here say the orientation so now I have a look at this grade and II of for this particular example him and I also put the 1 1 old direction parallel to the rolling direction that is actually a relatively common orientation that the grains will have in a sheet of low-carbon steel that's been rolled from there and now I I focused on the 1 directions as you can see them now they're they're well-defined now so that it will have on the orientation of direction we 1 specific orientation and for this particular grain with this particular structure no obstructive but just oriented right so I know I do this this grain I was here and know what I do is I extend these axis is the very far out of this crystal who till they hit my sphere that I have drawn imaginary sphere of drawn around the myself today and I do what I do is I make Estero graphic projection writes zero-gravity projection is the following and I looked at the equator playing that's a slight grade plane here of my experience and I connect the points where the and 1 1 1 0 Hi axes intersect the fear that this is the sport I connect with the the apex yes office of the law .period here and there the South political South Pole of my sphere here and then I registered the intersection points located so I can basically do this for many grains largest measured the grain measured the grammar and put all these orientations all these different all along Hi polls on this plane in an then I can just use this projection yes this graphic projected as a way to we presented here so let's let's
see again how this works so this is what I just explained the for a single crystal my stir graphic projection will be there's this circle playing and these 3 what we call this 1 pollsters and new so this is this .period this circle geographic projections and these are the sweet for a single Greg and say I do this for many Koreans I look at the grain next to it and mixes and well if the material is texture this then that you all have other yellow points which will be closed to the original report this and all have many of them of course is many of our measure a lot of people that many points and you can see here these single measurements so I can no the use this notice and it mathematically yes change this into a pool of density that would give you an idea of all right it is in this area as I have 4 times the the poll density I should have if the orientation was totally random tests during dismissed only random there will be no but you know that there will be a year of definitely poll here right there so as to the pole density allows me to mathematically see how strong the the tech shares delighted that it's basically a mathematical step here you go from these discrete points to describing a poll density it's a universe and and then that of course is not very practical this really representation so you represented to the net instead of having this this poll densities these these peaks here you you just have density contours as up and and this appears to be bold figure but as the very common way to represent the texture preferred orientations or absence of those preferred orientation of the problem is that with this approach L you don't capture all the texture components you don't capture all the text and there may be grains that have a specific orientation and grades which have on other specific orientation when the attack Schering doesn't have to be all the brains Of the same preferred orientations half of the great skin prefer to be in 1 direction all large another large number of grains are have that specific orientation at rotated by 30 degrees for instance and so on you wouldn't see this very clearly at end you would need to use many poll figures now I'm so what
people love the data that is they came up with the idea of using orientation distribution function and approaches at the front and you know that if you have any yeah but the laboratory coordinate axis reference coordinate system and you have another or Tobin all coordinate system other orientation have to write you know that you can rotate 1 of them into the other yes you can describe it the relative orientation using boiler angles this what think and To do this you need to be Oiler angles so with that and I'm not going to go into we all of which have we works you should know this from from Mass undergraduate method anyway so to chew orthogonal axes you can we late they come to their orientation using 3 angles and that's the idea basically so you again have your material material you define it laboratory coordinate axis rolling direction transfer normal directed its 1 and then you have a CU know steal you have a CU unit cells and so that means you have another set of the orthogonal axes and waste the and you can describe their relative orientation my only Anglesey needs we or the angles for so France's this grain here knows if I have the story or the capital 5 5 1 and fight to yes I know the orientation of that particular grain relative to my laboratory in accordance is so
I'm so let's see how this works so we have here at 3 D representation all that all year space we have the 5 1 in this direction fight to his erection capital for this direction do not ask me why capital sigh axis goes down right I have no idea why did the at that all this is no profound reason cited so it but that's the way it's usually represented that what the Lizzie access down of arms so I mean Orient any point in this what we call by the space is an orientation but so with which you can do in In this approach to description of texture is every orientation of drain you put .period In the grass root for instance this point here corresponds to the the crystal when 0 1 plane parallel 2 the the she knows and at borrow 1 direction parallel to the rolling director this particular orientation would look like this here you can see 1 of the the old 1 axis parallel to the normal direction and in this direction here but 1 1 all direction parallel to the this is this would correspond to this and of course the point here 0 0 0 means that basically my unit is oriented perfectly parallel to the the unit sectors of my units of parallel to the laboratory references so that at any point here yes will give me the a specific oriented so that's single grain there will be a single point there if I have many grains of course I will get many points if my material is of randomly oriented at these points will be be distributed all over fighters States there will be no but what we eat what we see is that there is a clustering of the ports and because of preferred orientation of so again this is not very convenient to use the single measurements yes what we do is we create a that into dimensions we create it but the density plot we make surfaces of the call the density of the orientations 10 right and then 3 the representational also not very convenient has found and with we have the most of the time do is we make sections through the space if we make a section through through this Chu if you want of orientations that this is
what we find so in In in steals and forensics steals in the important texture components tend to lie on 1 playing indeed the space and so on and that plane as defined by the fight to unload equal to 45 degrees is that that they're in that section we see we can see most of the texture components yes and so we can analyze very quickly about whether or not there is a strong so what's your only on the left is a picture of this section where we have the specific texture component specific orientations yes and and here we have the actual what we call the orientation distribution functions and its bases section through the border space and these lines you of a density contours of orientation so that means that here we have lots of orientation lots of grains are you have a lot closer disorientation loss of grains a close disoriented and many grains have orientations parallel lying extremely lying along this why is and and this this like this line here and this line there there there there called the fibers and with it because they correspond to fiber textures this fiber here is called the gamma fiber and it corresponds to the grains with a 1 1 1 axis parallel to the sheet playing yes this 1 here is the alpha fiber nose and it's corresponds to grains with a 1 1 0 direction parallel to the rolling direction yes the that's how we represent texture in In terms of polycrystalline materials and 4 and and still soulful forensic still it's different for no also that extinct so you have all the preferred orientations and the the detection the yes look different of course OK so let's just this is just like to make sure
Everybody was understanding what would peace concert was that this is also a feature of also put it on the year the class so you can printed out in most of the of the material if you want to write so let's continue where we were the the last 2 years after
class Tuesday 1 of you it
was you that was it 1 of you came to me and said was a problem with a woman the formulas under that was right
to life In meanwhile
corrective lens but to stacking fault and the right so so here In this formula here I had I'd written did he where we have as gamma just written down right that should be enough ,comma that's it for us it's not there is an energy to the fuel could repair that but to let the continue where we had the left I I think we have to show it get and so I already told you that there were 2 fundamental differences between there was fundamental differences between gunmen that equation is correct yes yes the equation with 3 distance that is is this is not right to it we had said that the fundamental difference really the gamma iron and all Semitic steals and hellfire and Fred excuse is that the stacking fault in In also nite you can have depending on the composition and the temperature as we discussed you can have very low 2nd fault energy 10 military choose square drew about 100 and spend more and so depending on the alloy used studying it in a very narrow the dislocation which wide dislocation dissociation from which the totally different from the young stacking and very very high and so it it disagrees and never dissociated in aphoristic steals or alpha can and will see today that this has an important impact between we discussed these to buy things here on the the the fact that when you playing around with dislocations dislocation reactions in the Austinite you you will be using this handy tool 2 meal to describe the dislocation reactions it's it's detector heater which consists of glide planes in the in the Austin area and the edges are Burgers vectors and the associated Burgess and that you have different subsystems NBC seeing there 1 1 0 planes are prevalent say something more about this today but 1 1 0 planes of prevalent flight system so this is the Rob rhombic Boddicker he draws again all the planes here 0 1 1 0 planes and the edges are Burgers vectors and they are 1 1 1 so be upon 2 1 1 1 of the factors and using very convenient to much more convenient than the conventional units sell as because they allow us to quickly see you know what to believe what happens to dislocations but again so this is where we were but do you remember when I was there I'm talking about about that Thompson Tetra he dropped the statement you can see so you have to you had that will just use the noted the letter notation rather than you know we have a B and C .period this this point here this pointers being and the ABC playing areas you can look at it like to notes it's the same as the 1 1 1 plane and then we had their here in the middle here we had this Delta and so this factor here we saw can dissociate into the stew vector so-and-so and rewrite the reaction of 80 B it is Delta was known to be linked to this reaction that have began there is a convention to take into consideration instead when dislocation In the metals and Associates yes and if this associates into pieces with all this I know where you .period where do you put the delta and where you put Delta the well it depends if it depends on what kind of stacking fault you have you remember we had to 2 options of stacking faults is 1 option was to have a 2nd faltered looks like a little sliver of the HCP the other option was to have the study for the looked like a little sliver of 20 in and out so it basically depends however I told you that they it in most metals and alloys well these stacking fault it is in transit entrance so it looks like an HCP sliver the why is why would that be well in general the argument is when you make an HCP sliver will initially be stuck involves what you remember what we did is you can the look at it as if you had removed a plane removed a crystal of a lattice when you have the other type of stacking faults which looks like a little 20 the equivalent of the way you can make it does this by inserting 2 but this place has been put to lattice planes in the extrinsic Sandoval have a higher energy then the intrinsic saying so that is the reason why we see intrinsic stack up and that's the reason why we can calculate the instant
exec using free energy differences of gamma epsilon has also but if it if it was a 20 1 with the twin has the same crystal structures the the sector for and you basically 0 right not so absences transit and so when it when this happened when we when we have this year the the the delta based on this side in Delta be respond that side herself so if you remember this year right hand rule has OK now if you want to go 1 step further and you almost always have to do this in the SEC because most of the time and dislocations are associated as you do the same thing legacy of and then when it this dissociated you need to know I know which 1 is left which 1 is right the partial With the Roman letter is always on the right so right I just of course you know you forget this yeah so I use really remember this right by thinking Romans are always right this is a member of the memo technical way sentenced to remember no so just because for me of course this is convention you need to know it and then but it's it's it's so it's very convenient and the reason areas but you know when you have dislocation reactions in SEC metals and alloys such as also medics deals when they meet yes the 2 partials may be reacting with each other forming another partial and if you don't have to be the partials correct you know you may end up saying Well you know they will repel there will be no reactions or would have liked to you in order to understand a little more advanced concept and will see 1 today when we talk about the lower Nova lox you know you need you need to know what you need to know but again this is something the conventions and important to remember the convention in the to that sort again . start talking about partials enough for a textiles so Al-Faran right you will really greatly upset me and don't talk about Thompson contributed to a to describe dislocations in Alpha our right there's no dissociation Alvarez and you certainly never use the Thompson contributed he drove to analyze dislocations in right but so the Francis remembered in the loop we had this location will go on you can say for instance that power so this would be for instance gets him say we have a lot of things like disorientation and I have here a dislocation loop on this plane in so let's let's To make a tool which metrical along with this so that and let's say this the Burgos factor of this desecration of business in this direction it's B but a B-grade that's the bird Specter so I'm going to use my my role here so I I've said it signed an award Debee years so now that you have to get to know where the extra half planes are I have to defined directions so so what would I do know is like OK this is my the vector in and here knows I'm going into the edge orientation that that it's the right look here it's edge so I have to be here with you as this is is going around right he was going like this that it follows the line so I have you in this direction be in this direction so extra have plans are up on the side and on this side the B is the same but you would now points at me the points at the pointing away from another pointed me so the by do saying this is my line direction by Burgos factories there still may be so it's like this the to have players are down right and and so sorts of you my happens about up you that of course when it's dissociated as it means that the disappeared actually looks like that X 2 extra have planes pointing out and to accept what happens pointing down and so what you need to have also also noted for defying many of us would have a look here so I said to a B is a Delta Delta being has so Delta B is on their side but and a Delta is on the side of the Romans of this was years ago Delta is on the right and so it's goes like this this this you don't have this and Delta be despondent left it's it's like this 1 and it's the same around here all around him so that this factor so the inside here this is From this side this is the a Delta rented state Delta everywhere everywhere in the delta this partial dislocation so here the extra half plane is up here the extra half plane is down so that the loop can still collapse so when the illusory the become smaller and smaller as this extra have playing well the day come together with this 1 and the dislocation will disappear from that that's as it should be of this and then went to knowingly to jump I had here because it was
just some think something that had
right now we come to a 2 2 2 2 2 this here and it
yeah we introduce the concept of allying tension that is similar but not the same as in the surface tension of of liquid for instance when you have a liquid film like a soap film and you you you can extended to send the surface the surface tension yes will make it such a you you need to apply a force to make this surface larger so we have something similar in 4 dislocations and we call this the line tension and of course it's related to the energy right so it's the brevity of the energy basically but and what it basically means is that the if if you'd imagine dislocation as being of a of wire when you it will always want to be restraint and so I don't know if you imagine actually they are this is list this location all by itself now you you can and will be very very often in the future I will instead of talking about dislocation yes I will talk about this location segments and basically that's a piece of this location can be short or long whatever that is the stock at some kind of pinning points so it's like this is like what the dislocation is like a pen and these 2 positions that the reason why we use this image very much in in practice this is because that's usually what happens to dislocations they are a they did they not know big dislocations which don't interact with anything that's and in your brains out most of the time to just run into each other just as and a pin each other or you know if you if your your stealing that contains precipitates an undeniable run into these precipitates that will prevent them from moving in or out and if you have allying elements they will run into that particular following element and be more or less by the presence of this analysis and that's why we know we usually think of dislocations not as long the dislocations but as the secretion segments of dependent that's OK so this year we have such a dislocation segment grew and we have a new we apply certain forces to this segment and say the the forces of such that dislocation that no takes on a certain this circular shapes to you you have to imagine here I have some kind of sheer force which held power yes and no so I can you remember we have we can calculate what this force is on the dislocation using the peach color formula and I'll earlier so that forests will be tout times to divert the specter of this section right good and now if I would cut a piece of this dislocation out of 2 this location it would job In order to to keep In the same shape I wouldn't I need to have something that balances the the force I applied so so I kept this year's said this is very scissors like kept out and I look at this peace and if I don't do anything it's going to run away right it is because only this for so big that the balancing forests yes and the thing that that it keeps the the dislocation in equilibrium that still lying tension so you you imagine it as being a vector the longer these at this location like this and there remember it's where it's at the center of a few moments later previously sectors this force is related to the energy of your dislocations derivative of this energy and the engines and so we haven't based on that we know what the a size typically areas of the the line tension GB square over there Of course this equation is is very simplified equations that doesn't have a lot that the it's just gives you an order of the pretty good order of magnitude but it doesn't know it's it's different the slang tension will be different depending on the type of dislocation you have there's depending on the dislocation direction etc. so you can knew there many more advanced formalist that this is a pretty good 1 to work with them and certainly in the in this erect so so this is the same thing here so we assume that we will very often assume that the shape that the dislocation group has Is this a semicircle is a you know we can look at it this as being a segment of a circle does it again it does not necessarily have to be this way but it's a good approximation so if we have a segment of the Al in the Mongol here is called the Teeter and the other the semicircle has certain that radius the bridges of curvature so the yeah lining the attention has a component In the horizontal direction and component in the vertical direction the component in the horizontal direction they balance each other right used to balance each other so what is important here is the the vertical component of the the underlying tension that you have that you have to consider OK but so we can do some of the really interesting calculations even with this very simple models so bad the 1st of all we have we look at what is the size of these the vertical component of the line tension so that is why I have 1 here this is so do the projection of tea in the vertical projection you can easily calculated because this article here yes is equal to have this article From geometry so and that means the force on the dislocation is times B To be multiplied with the length of the dislocation which is detailed in this so the town PDL is balances the Times the the 2 of them and will DL here is this bundle the T 2 times are on the DL can be replaced by far the theater has now I take these 2 equations together and I just say that express the equilibrium of forces that this year is equal to that this and that I can no calculate the relation between the radius of curvature and that the deal you applied externally applied so it is obviously if I have a very large should force the Arveladze are will go down in noble have more circular shape to the dislocation right so let's go to this this equation that was down here is now up here so that so there is a relation between the there applied the sheer force on the slick plane of the dislocation and the radius of the dislocation and there is saying an example here of how you apply this form of differences in when you fatigue materials new fatigue steel but you know what fatigue as is right to have oscillating force this and new plight is for thousands of times yes I will if you look at the mike Estrada of the do this deal then I would you find out is that you've got is incredibly three-dimensional organization of dislocations you have very dense dislocation bands here and then channels with almost no dislocation that's 1 thing the other thing is that these bands consists entirely of the edge dislocations whereas this the few dislocations we see the are is located very interesting and intriguing Microsoft what you can do what you also see instead a brother regularly you you see that some dislocations are it's a semicircular looks like like the 1 they're on top when I can do is I can now I'm trying to imagine OK could there be any stress In the material that will cause dislocation to 2 assumed the Shiite stress for instance due to the presence of the snow high density of edge dislocations and that's so what I do is gone the measure the radius of this slope here and I and I plugged into this formula yeah I don't need much more new and much to calculate because GE is the sheer motherless and B is my vectors so I know these things applied this and and 5 27 will make a pass so you can actually use this formula if you have in your might prescribe too managed to Freeze yes there the position of the dislocation you before you make a sample albeit before you remove destruction to work but obviously but in this case there was no external strategists stressed inside the material internal stresses but in other cases human you know the dislocation will assume much certain should because you apply an external stress right in that case to freeze on the the dislocation of position you will Francis you radiate material yes so you create lots of point defects which will pen the dislocation in there stress positions and then after that you make a sample and you can you know you can measure the the shape of the vessel the rigors of the dislocations and then from there to determine what was the shear stress on these dislocation we're just using this equation but it so far now let's look at an essential difference between the far-right for Riddick steals and losses the big difference with which witches direct consequence of the stacking fault energy is the way Crosslin happens you can but so let's just system look at the bar of soap BCC's slipped into and out so let's just say I have this you know all the edges Burgers vectors and so I on looking at the plane there as I can see that have for edges 1 2 3 4 so I have Bloomberg a specter of course the stewardess saying yes so I have to go to the respect actually still have 4 because I have I can have respect in this direction and in this direction to the actually before right if I take into account the signs of so let's say we have that evidence for trade and and have a dislocation here so just to make my life a life easy and it I will just make it nice and rectangular and so this is diverted Spector yes and also for the sake of convenience I don't if all use it but let's say I've also defined the line direction threat so indeed In everybody CIA and so on say this by applying the stress In the dislocation loop the size of the dislocation increases right what happens here with what what can happen when the dislocation encounters this place all let's think this Burgos factor is the same as the service sector so if I had instead of having this situation if I had had any similar dislocation here like this that piece of this location would be exactly the same as that and so forth these pieces of dislocations yes you can you can get what is called crossed this piece of dislocation conscious the moved move from here just because prevention program here still here but when it does that it's on another going play and it's Crosslin now it cannot happen to all the segments of the dislocation it cannot happen to be the case hearts yet because the edge parts there are some respect like this but the line is in this direction right so it cannot go into the other swiftly another all right so only screw dislocations can cross line only only screw dislocations can cross but they only Chris Coons segments of dislocation now OK let's continue our story here tonight I have I have this this place is the same as the same as this 1 orientation wise but it's it's not the same playing its parallel to this 1 but at a certain distance know what happens if this dislocation that's now here which used to be there the decides let's say because of the applied stresses that's too it wants to go back 2 plane that's parallel to this there's no problem it can just go here so I can have dislocation moved but Del to another guy playing this by crossly let's do the same with about it's the same with that's the secret still so the move there's something this case I think need to put it down on his wife Laura OK so let's see what happens here if in this case let's say we have at this location here this and this will be respected in the Mainland election focus that is its location sighs increases then crew part arrives at this .period yes so this plane that's that's display was also glide plane this Burgos factories is also the Burgers factor in this playing so this location can move the screw segment can move into this plane also can also cross How ever and this is the big difference Our dislocations here In the SEC they are disassociated yeah so the Burgos factor here isn't parallel to this so let's see students let's say it has this vector this vector and the other 1 is this vector you can see this vector here is not a factor of this plane yes To the dislocation cannot glide into the other and like the other blight because it's dissociated and and associations the partial disorders or not Burgers vector of this across way so no no no cross slip on last we managed to pinch the dislocation pushed it to partials back together yes and at the end and removed dissociation so this is what happens here this is what I just threw there you have won this location nearest the school segment here if it's dissociated 1st I will need to remove from the dissociation then I can get at cross like this and then of course the dislocation will again this ocean yes making it again difficult for dislocation to cross slip again if that happens when you have a low stacking fault energy yeah steel if you have a high very high stacking faults materials steel then of course it's there is no dissociation and end across slip will be easy no In deals we have huge stacking fault and so there's never any problems for the screw dislocations too to hop from 1 glide plane to another 1 this and that is very very a fundamental difference because In the case of the far-right and forensic steals your dislocations can easily change glide play they easily changed lightly so if they run into an obstacle or whatever yes the solitude another dislocation of precipitate this they can just Google rounded the Jusco changed light planes circumvent the obstacles not so stacking faults antics steel there this locations will tend to stay all there original glide being whatever yes and so on as a consequence of these 2 the crisis of very different strain hardening behavior this material string Hargis much less than this 1 because Crosslin makes uh the obstacles let's efficient has been but it's so I think they're pretty good moment to stop so you let it sink in as it were I remind you of the fact that the today's Thursday that that tomorrow at 3 o'clock we have we meet here again for the for the maker of classes the and that's the most important point I had to make thank you very much


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