Modern Steel Products (2015)  lecture 2
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Title 
Modern Steel Products (2015)  lecture 2

Title of Series  
Part Number 
2 (2015)

Number of Parts 
31

Author 

License 
CC Attribution 3.0 Unported:
You are free to use, adapt and copy, distribute and transmit the work or content in adapted or unchanged form for any legal purpose as long as the work is attributed to the author in the manner specified by the author or licensor. 
Identifiers 

Publisher 
University of Cambridge

Release Date 
2015

Language 
English

Content Metadata
Subject Area  
Abstract 
A series of lectures on steels, given by Professor Bruno de Cooman, Graduate Institute of Ferrous Technology (GIFT), POSTECH, Republic of Korea

00:00
Finishing (textiles)
Gas compressor
Saw
Pattern (sewing)
Roll forming
Computer animation
Alcohol proof
Spare part
Book cover
Rolling (metalworking)
Surface mining
Steel
Steel
Watercraft rowing
06:43
Typesetting
Vertical stabilizer
Hue
Train
Pump
Saw
Sizing
Roll forming
Computer animation
Institut für Raumfahrtsysteme
Diaphragm (optics)
Steel
Steel
11:51
Mechanical fan
Nut (hardware)
Typesetting
Ink
Mixing (process engineering)
Roll forming
Turning
Brickyard
Automobile
Canadair CL44
Alcohol proof
Institut für Raumfahrtsysteme
Tool
Steel
Tool
Ship of the line
Progressive lens
Vertical stabilizer
Monorail
Train
InterCity
Space suit
Outsourcing
Computer animation
Cartridge (firearms)
Thrust reversal
Ship of the line
Steel
Tanning
23:17
Vertical stabilizer
Typesetting
Semifinished casting products
Mat
Hot working
Gedeckter Güterwagen
Computer animation
Alcohol proof
Institut für Raumfahrtsysteme
Spare part
Steel
Steel
International Space Station
26:54
Typesetting
Nut (hardware)
Ink
Saw
Turning
Rep (fabric)
Computer animation
Ship class
Tannin
Steel
Ship of the line
Steel
Material
RWE Dea AG
34:33
Matrix (printing)
Vertical stabilizer
Ink
Car seat
Stud welding
Wood drying
Ammunition
Turning
Roll forming
Casting
Rep (fabric)
Computer animation
Cartridge (firearms)
Ship class
Spring (device)
Musical ensemble
Ship of the line
Steel
Material
Cylinder block
Last
42:30
Blast furnace
Game
Computer animation
Alcohol proof
Typesetting
Ink
Steel
Material
Progressive lens
49:41
Vertical stabilizer
Typesetting
Stagecoach
Fiat 500 (2007)
Ramjet
Nut (hardware)
Stagecoach
Ink
Towing
Chemical substance
Weapon
Finger protocol
Gedeckter Güterwagen
Turning
Computer animation
Cartridge (firearms)
Nuclear fission
Typesetting
Remotely operated underwater vehicle
Boeing 727
1:03:24
Typesetting
Matrix (printing)
Fiat 500 (2007)
Stock (firearms)
Suitcase
Computer animation
Cartridge (firearms)
Estudio Lamela
Typesetting
Plane (tool)
Matrix (printing)
Boeing 727
Tanning
00:04
so grueling we had to
00:08
started by I'm saying a few basic things on but Byron them to reminding there too it's a polymorphic you have 2 forms of violence that are relevant this is variety of Austinite Osmond's hightemperature form the although and this 1 here but what will be will transform verite as you cool down there a another former polymorphic form of violence called epsilon viruses hexagonal also exists but that exists a very high temperature temperatures and a 1 you will need the encounter it in relatively highly alloyed steels so most deals it's it's not really relevant but but in pure iron you really need huge pressures to here these are the crystal structure of very different they have very different properties on going from elastic modulus all the way to diffusion conscious in these 2 phrases are different on the chemical properties of different yes I and I but saying but In purer and this transformation from from hightemperature also went to the lowtemperature varieties said 900 12 degrees so pretty high temperature well we encounter this transformation but in almost all of the stew processing as soon as you well are around this temperature close to 900 of course depends on on composition the transformation will will occur this example for instance of where it happens In the hot strip mill this is the rolling mill you can see the trip coming out the socalled finishing finishes the finishing stands here in the hot strip mill hot strip when it comes out of this because into which called runout table discussed this in more detail as as we go in and that's where it's cooled yes and before its here is the list of coiled struck the rolling is strong he said that around thousand to the state Honduran and close to 900 deg C was that of the cooling here you cool this trip comes out at around 100 increases to 2 anywhere from 700 to 500 degrees C and and then you coalition and obviously but the transformation from the high temperature also denied that you role here too the for a take my constructor in the poster but will book cover In this here in so what would happen basically if we look at very simple steals the show that not much alloyed units I'm so 1st of all you you look at the temperature as a function of time and so with thermal Of those patterns that you see is that you can't that's the Red Lion Area 2 segments of the segments which closed down rapidly in a 2nd was not very slowly and 2nd goes down rapidly that's the 1 corresponding to this right table and when it is very very slowly corresponds to the new part of the thermal treatment when the cooling is very slow it's in the coiled strip so what typical calling rates here will be of the order of 10 to 30 degrees 2nd here it'll be 20 degrees Brower it's a very very different commingling and so on but so as is you cool there is a temperature here where when this transformation where would this structure goes into goes into this structure and this doesn't happen instantly this happens as follows you have these grains of Austinite here Green of Austin and the row of this Grain the transformation started his leaving white little white things here because of the grains of this phase that that start to grow and eventually they will replace this like this black here and that happens you certain kind antics involved in these kind Natixis are of function of the composition of the of the steel in particular and this transformation here from Austin I too verified the this decomposition the Austin 90 composition white wheat which means same decomposition because depending on what the holding pattern you as you can get different microphone you can have something that's for rectangle you can have like perspective it contains perlite etc. student and wanted that's what we say on the composition of Boston alright so obviously but the
06:44
crystal structure units of U.S. steel doesn't look like that's the reason
06:50
is because you know you have we're dealing with at the iron alloys and there will be 2 types of elements in this alloy and there will be interstitial atoms in these orders the small it's a carbon atom and nitrogen atoms and which will occupying positions in in in this unit cell that are coincide with lattice position with this coincided with higher position they will distort the lattice buying their presence and they will also as do most of the following conditions influenced the stability of the 2 faces now and they will also influence the kind that takes of this Austinite decomposition that's really important they do something to the lattice mechanically told distorted the starter letters may also influence the thermodynamic stability of the 2 uh polymorphic forms of violence has and they influence the kind that experience was the transformation about 1 of the things it's interesting to see his compare and the a look at the size of the actors you can put here In these injustices as In comparison the the diameter of the iron actor so you see if you know that you see that there these injustices of our very small in comparison to the size of these actions and the reason why did it does not look very big here is because I've made these atoms smaller so you can see the structure yes that's not the real size of the iron atoms Yonatan rebates and the kind of touch each other adjustment in smaller cities conceded crystal structure took very small um diameter is available indicate this is for GCC because of SEC if you look carefully here you can see that the size of the interstate are about 3 times as large about Wilson .period 44 so as a consequence if we put a common active in the interstate sees so there will be a lot of distortion of local distortion of the lattice and lattice distortion in BCC is extremely high and it's still high that it hasn't had a huge impact on solubility of carbon in bcc it's extremely low In fact ,comma is probably the is soluble in bcc IRA units the nitrogen also because it because lack strain is still here and in comparison and the lattice training in SEC ironies of the high temperature for the fire is much smaller and I do solubility of carbon in SEC irons in the hightemperature form of is actually the brunt of the fact that we opted to Weight Percent of carbon can be dissolved in gamma what happened when does this name is that of many steals contain carbon as an ALleading element you will see that and so when you transform the high temperature the lowtemperature form of irony this is going to be a lot of very high driving force to but I get the carbon out of the bcc lattice informed carbide another thing just for your information how do we know that the carbon is sitting in these particular October he into the sixties we know this from all the and materials science experiments that happened on the last decades and so we know where the carbon sits
11:52
in the east the Missouri many other intercity seized in the lattice but that's where did this would liked to say In case and this is what this distortion someone if it misses this opportunity to roll a interstices concede form of the drama and if you put in interstitial atoms in in a very large lattice distortion and this lattice this distorted is actually observed when you take Austinite dance and Yukon should very rapidly in the car but doesn't have the opportunity to former Carbide get away from the lattice and then you can observe this distortion and this distortions to tribal it's should tribunal distortion of the line good so we have an allocating additions would show such as carbon and nitrogen that are Indian interstices the social positions but there are other atoms such as scroll Molly manganese silicon phosphorus moment of Tucker these atoms will sit Bill substitute for Bayern in the latter and again just like the case of carbon and nitrogen they will have they will distort the lattice locally because they may be larger smaller the IRA so there be a change in the yard local change in the lab train in the lattice as you add these lemons to be on siren to make a steal it will they will also have an impact on the relative stability of the Austinite fairer and and and it will also influence the kind that takes of the Austinite decomposition of how fast the city also denied decompose into variety of constituents the rents when you add Molly manganese but these Adams a slightly larger when you get a small lattice expansion locally but you can have a lattice contraction if you put in silicon aluminum have to construct contruction by and so it is organizers said the impact the stability and the kind of text I would be interesting if you for you to remember that kind of chrome and manganese of slightly disabled on lattice parameter the irony is that Avery closed in the periodic table and close to the same but another important allying elements such as Molly is as much it's much larger at Pearsall a lot more what this distortion so I so when you once we start adding at allocating elements and they will have an impact on the the stability of the US Austinite and and variety and you may get other phases a different temperatures and so on and outlines and so you need a tool 2 1 the able to describe what happens when you add in an alley elements and and will use base diagram as a tool To determine the phases the number of phase their presence what phases are present the composition of the on the face fractions at different temperatures and composition and will also identify interesting Mike rastructure as such as allowing along like a structures his friends wondered you know that is in progress the iron carbon system her life and and were interesting all in knowing all the states because the mike rastructure influences friends a mechanical problem and this is the iron carbon phase diagram which as soon as all of you know in which we will always so for instance I just want to point out to
16:53
so and you know that this is the Austinite stability field and this in this field we have fairer plus when would use me right down a steep that heat is just a seem tight so what you see is normally a mirror at about 912 912 increasing the Allston the transformed to Variety s if we have a pure arrogance of pure iron is along this this line here on this diagram and you see for instance that and as we add carbon in as the 912 decreases to lower temperature and that means that edition of carbon the changes the relative stability of and Austinite it's it tends to stabilize the Ulster and there are elements that do just don't do the reverse this is so earlier in the week in with the space diagram determined there In particular in this the iron carbon phase diagram determine the fraction of Austinite variety and Simon tides as at any time temperature and composition for instance I have said have carbon content say it is 6 . 6 7 per cent In weight I haven't alloy that consist of that unit and I'm interested at a temperature of 200 degrees C so my question to you there's what is the on the other what is the fraction of Austinite variety and 7 tight In that the takeover a lot of people the 1st of all I need to draw a line at 200 degrees C yes that's so I see here that I'm definitely somewhere in the region where I will have fair right and seem time now and then I look up on my the x axis 6 . 6 7 2 this is 6 6 . 6 is is right here in this as this point and the phase diagram tells me there I have pure syntax has so this is alloy that is actually not real in alloy it's a Compaq it's it's the carbide of fire and it's 100 per cent this means that in this particular case situation with this dialog it'll be 100 percent of Stephanie there is no that's an interesting point to note is another interesting point that and we look at this at this point here at this point here is the it's a new tech toys and if I have a composition New Territories composition that I have I will have a transformation of Austinite true a mixture of variety time and what's interesting is that this is the way the transformation happens it gives me might Lamela Lycra structure which we call her life and in the Irish carbon system this is approximately if I'm right ,comma researcher that approximately 0 . 8 per cent all right this particular point in us occurs at around 720 degrees here the 20 degrees and that as I said about 0 . 8 per cent ,comma hands but as soon as you add other elements to use steel this on the position of this this you take toward .period can change can change a lot actually for instance if you had typed Tania this Utrecht toy temperature decreases a lot if you add Nicola decreases also but slightly less so at a time when most elements will reduce this temperature will reduce system then and this is experimentally whether you measure and that had 1 of these elements of this Utrecht on temperature decreases but know the thing that happens is that the the composition of the new territory .period also changes and so what excuse me what source I got a little bit too carried away is paying attention this is this is the only Utrecht ordered the composition so as you add elements it moves to the left the values news and then it all such the
23:19
temperature changes the temperature changes as you add elements and certain elements this is about 720 here in the winter degrees C certain elements will increase the power of this the temperature of the elements will decrease so for instance of which with the Tania will have a very very strong inquiries silicon also said that basically means that instead of having this downward slope here that this world may even increase as you add them tightening elements like this that have similar effects as tied to these elements that increased this new tech toy temperature 20 new quality cruel the native we call them farright stabilizer for Alpha stabilizing elements stabilizing whereas elements that reduce this temperature and we call them Austinite stabilizer or gamma stabilizes and as you can see why that that would be elements that we reduce the the new tech toyed temperature will increase we also nights stability range and then there and so they may stabilize .period it's WorldCom stabilizes Austinite stabilizer on gamma stabilizing alone right
25:12
and so on what would what is important for us in this whole phase diagram yes it is it's actually only this part we we really don't work with this part only up to about 2 twoway process that's point number 1 and that many of the steals we deal with it but are actually In in this neighborhood so at only the IRA rich side Of the phase diagram 10 but let's learn some vocabulary here so 1st we already know a few things we know that this point a scolding tech toys .period we know it's about . 8 2 leads and more exact . 77 and the temperature is around .period 28 . 27 this particular it tastes good but and then the new tech toys .period and so we said of steels that contained less than . 77 carbon that their Hypo you tech toys highpolluting less In New Territories competition if if you're above and as we said we say the hyper you on him he said so basically we have 2 types of steels Hi poll Utah steals the right
26:56
so if if we're very very close to the y axis we will only see in the microscopic true we will basically see only their please stop this is the right
27:14
that means is that face composition that are very close to this this red adopted him as a and are steals the particular type of hype we attempt to steel and there's not much to see here and the remaining steals that basically look like that can so so we're talking about steals that are in this neighborhood and in order not to actually see a or be able to describe what is going on in the steals I have to blow this up all locked so if I blow this up the businesses .period 5 years like a magnified is 10 times now I go from 0 . 0 2 . 0 5 the point all 2 0 . 0 5 per cent of carbon so this corresponds to what we call 500 ppm of carbon 500 weight ppm of carbon corresponds to so that that's 500 times 10 to the minus 6 500 over yes millions so so so this is 5 times 10 to the minus 4 if it's if weight fraction of this and steel that contains 500 ppm of carbon in weight ppm means that there are 500 grams of carbon for every million of grants of material that to this fight and sent to the minors for this the weight fraction and and and so if I want to do it in percentage multiplied by 100 so that gives me the 5 times sent to the minors to at the end of this the weight percentage all point .period so you can use by the way % that's used very often in this in the industry you can also say 500 ppm and In scientifically we like to use a mole fractions yes or atomic Percent things like that so you you you see in different ways of please send the effects in general the industry will double list of weight for weight percentage so if we blow up this corner here and we we see see that and that is something we can't see really here is now that we have a region here a region where we see this is fair right variety which contains carbon in solid solution so and we say can save then we can also see what the maximum solubility is of carbon In the fire and it's it's about 200 ppm 200 ppm the 200 ppm 0 . 0 2 per cent that's the maximum solubility of carbon in variety in Allston nite the maximum solubility is here as you see here I can I did it and carbon up to 2 % I still have hope which he news Boston to assess 0 1 2 so it's it's it's but a very large differences in insoluble the solubility itself of of carbon being uh In fair this is actually a given by this line here this line here is actually the solubility life and this is the solubility line for carbon in variety you can say for instance if if at all well let's have a look here at 600 deg C the solubility is at 600 deg C solubility is 0 . 0 4 0 5 % apartment so that corresponds to 50 ppm government so it but as we reduce the temperature of the the driving force Florida pushing the carbon out of the the lattice is very high you don't have to come to class right don't have to come because we taping the class anyway but if you come to class please don't text of if you want to Texaco good text do whatever you want to attend a lecture whenever you want but don't play around with your mobile phone to the right so there you go don't and adds so yes as a side as and many steals in this some type of
34:35
a carbon content ranges and when we we talk about lowcarbon steels but you know that's the kind of carbon contents of new dealing with look OK it's so let's now and increase the carbon content of to the new tech toys composition here and there and describe a little bit like this that you like rastructure we we observed that when we cool down Austinite with this point 77 per cent of carbon and violence after at room temperature this is which would we observe the Lamela Mike rastructure where you have Alton mating layers of variety and soon and call this this this is Pearline perlite is not a phase and some of the faces those 2 phases that that result from the transformation of Austin s and the way transformation of curse is by this Lamela growth Our submit it's it's it's it's a twophase Mike rastructure sold out things like that very nite or Martin inside all her life they're not new faces right on their chests and in order to describe them but we can't use the word phase we we say constituents I try to use constituents in the area when when you're describing the these constituency so that if if if we go beyond missed 2 per cent here these alloys are very important in the world but that this for a class of alloys that we do not discuss it in this class and musical cast pirates from this an example of the cast iron here of which contain nonJewish graphite very interesting material but we need so we not talking about following with carbon that mordant interests now many steals art basically Baron carbon Alex Diaz and depending on the amount of carbon we we have in the alloy will get a different face fracture but variety and that the problem is but when you look at the mike rastructure level you don't see verite brains and Austin are extremely thorough grains and Simone diagrams separately which you see verite and perlite this means that the tied forms perlite together with a fraction of the the variety thing so for instance here so you can see this is a situation where I them said the matrix is offering grains and in this matrix you have quite a lot of her life I increased the perlite content more ice and get a situation where the matrix is perlite then a little bit of another phase in here which is similar some of little blocks of seats in the spring but basically we're still dealing with variety and and seeming to accept that the microscope microscopic trip is different because of the the new technology transfer so let's have a look at trying to understand these migrants directors so we we go through this interface aggregate tells you if you go from high temperature to low temperature OK so at high temperature you always have also tonight that we will you call down the phase diagram tells you you will have the right and seamen died and depending on the composition of you will have a different face fractions but what you actually get In the end my constructed is is actually more complex so and it's and have a look at what you get if you have high pollutant toward steel Celestin is about . 8 percent of Carter that you have this an example here 4 . 2 per cent you 4 fair and then verizon matrix and then in there you have it perlite as I increase the carbon content I get more perlite you can see here from point a to point 5 and a much larger pools as it were of if I go the amount the EU territory .period makes a difference if I go beyond here when I call them the Austinite the Internet pass this line here is morning I'm going to the stability arranged where you have Austinite last season ties so I the 1st phase on this might restrict your here instead at the grain boundaries of Daedalus I form tight and the hazardous as the primary Samant I bond for very much and as I call them the 727 whatever hasn't and transformed becomes life I can explain it is very large perlite grains him with the 1st phase to form is this seamen died as as in this particular case when you cool down the 1st phase to form this fair I think so so won't detail here
42:04
.period 10 percent . 37 . 55 . 8 you can see it as I go from left to right graduating the the farright grains are we placed by perlite constituents eventually at that point 8 everything is permitted this
42:35
is that this this typical Lycra structure and you can see very nicely he's alternating layers this is not so true it's been a stable like rastructure clearly winning like restrictions that we that we have in steals or not stable Lycra structures and this is 1 of them you can will see in a moment of it you can change just like rastructure the reason why it's not stable it's because it it has a very high energy and there lots of interfaces here that it is is the reason why you have high energy but
43:26
let's it concentrate on this particular Mike rastructure tried to introduced the some concepts about the kind that texts of transformation so Will we will look at this particular transformation has From Austin 2 this mixture of variety was seen time which we call her life to normally this this transformation should occur at this new tech toys temperature 7 . 7 but what we can do it this I can say I have a lot of foreigners and and have a furnace at 800 deg C as far as I can with my material might steal in that furnace for a while still it's set at 800 deg C so I have missed composition at 800 deg C stands by its hold the prisoner tells me it's homogeneously Austin and then have another its next and so on that furnaces can be for instance 650 by take sample and put it in their efforts that would I'm doing it and I thermal transformation of the at 650 the Austin I'm not stable and more and I and I will get the transformation to transform the formation of her life act 600 and 50 deg C and I came up to the difference between new tech .period temperature and the temperature at which I do the transformation that is called The under cooling I can have a very large under calling it can go and have a furnace where I do the transformation 400 degrees C at 300 degrees C I can quench my sample so I can change the under cool and look at the kind that takes of the transformation in many ways in which we can look at the kind that exposed the transformation the but safe we have a way to that do this transformation and follow the progress of the perlite formation at different temperatures in the laboratory and you can do this in a very simple way you can use a very simple way but you take small samples of U.S. steel and we measured the light In the length of Europe of their still 2 candidates at high temperature and a kind of gage that measures of the light him and and you call the material to the a lower temperature so as to what happens when you cool material its strengths right thermal expansion through contraction the absence of strength it gets little its so this is the for regional but materials so it will shrink because of thermal contraction but something else will happen of course because I will transform Austinite to farright and right and so what happens there is that the latter's the statement noted also might like this is a very dense lattice it is a very high atomic density when we transform to farright the lattice isn't that much less dense so the same amount of atoms has a larger volume N that in other words you sample expands because of the transformation tho there is a thermal contraction but there is a lot of acts of this sort this contraction due to the the rule contraction and there is an expansion due to the transformation the transformation Austinite to ferret lovers since then you can just follow this measure and by tracking that you can you can get the kind that exposed the transformation recently so if you do this right would you find is that when we go back to right when this under cooling This is the delta T this under cooling it is large you get this green light phosphorylation if I reduce the under cool instead of interest rates 6 and at 650 the transformation is still work In other words takes more time to get the transformation to finish if I do it at 7 6 75 under calling is even less transformation is small this is slower again that but with the goal but you just go back here so what
49:46
controls the the growth of the perlite growth in the quality of 2 things yes carbon redistribution is the carbon doesn't like to be In the farright because his no solubility so it'll for it's got a diffuse away From the farright at 4 it's so that it takes time but there is another aspect and the so did the carbon diffusion is related to to the growth of the statement eyes the other aspect is nuclear nations so the the process of transformation formation of perlite is a process of political the process of nuclear radiation and the many transformations that's happened by this process so what so what happens here so when I look into detail in this S curve of transformation kinetics has I have a nuclear nation states and then the particle grows and grows and grows and grows and was eventually economic growth indefinitely because the volume that transform is limited and then at 1 time these growing perlite islands will start in impinging on each other so and that's why I knew you get this S type of current as of that date the kind that takes and reads saturation the slowdown so you you have a face of nuclear Asian growth and and saturation so what we find when we look when we look at the creation and growth processes is that the rate of new creation it time when the under cooling is large so when you carry out the transformation at lower temperatures indeed rate of nuclear is hot the growth stage this growth stage here the growth stage is high here at higher temperatures and that is at small under cooling and then you have the infringement states which is basically about past you know from the normal of results of the the 2 groups and so so why is the nuclear nations in the nuclear staged you get a large rate of nuclear nation when the temperature you the transformation of Ludovic that's because the driving force is large the driving force Watson was a driving force in the transformation is the difference instability between Austin infer if I had a phase transformation this is also my saying look just let's just look at the pure Austinite and verite units of this space has a certain stability that's and you know that we can represent the stability of the faced by means of their free energy units and in the farright also has a free energy and if we energy is a function of temperature and composition and if it's a pure substance its only function of temperature found so so if I do all this is a temperature of minus 1 so if I do a transformation very close to the I want to do this transformation temperature the driving force will be small it is a sign of at this temper at this temperature the driving force is 0 but because they're equally stable the driving force is basically the difference between the free energy but the lower again the more stable there I becomes relative to the Austin and so we say the driving force for the transformation is higher as we this this would be the founder cooling Delta the if the under becomes larger the driving force for the transformation is high and that has an impact on the nuclear age if I have a high driving force I'll have lots of nuclei nuclei for the transformation of under the plan the growth stage we're dealing with a redistribution of actors a carbon atom has to move away from the far right into the same entitled that takes time but that's controlled by them if you say 50 of carbon this this is controlled by the difference and free energies this this is controlled by the diffusion in this particular case the diffusion of carbon yes OK so these 2 processes theirs both we usually like to say was nucleus and growth process but it's not like there's a nuclear nation process and an afterdinner creates present is a growth prospects don't want it to processes happen at the same time so lectures show you what it means and you haven't depletion rate which is the number of nuclei you form per unit time per unit volume and you have a growth rate which is the increase in the radius of the nuclei with high so if you start with a unit volume say off Austinite were beginning at time 0 at certain temperature after a certain time you for for instance to nuclei in this unit volume in this would be to nuclei of of perlite and place all nuclei early and then at 2 delta T these nuclei have grown To a certain radius yes which areas the radius as the growth rate times a day the Times staff OK and and so that it but in that same time you have added to nuclear that's because the nuclear nation rate is that remains the same and then the next step the original nuclei have grown again the 2nd stage nuclei have increased their radios and you have added to warm clear that's that's the process you have McLeish and growth of current
58:05
so if it if I if I show know what's happening so if we have the the transformation very close to the new tech torrid temperature we get the lower rates of nuclear fission because there's not much driving force but with a high growth rate because the few diffusion is easier at higher temperatures at very low temperatures we went to the transformation very low temperatures the the completion rate is very high I have a lot of driving force but my diffusing 58 is lower so I care growth it is coming in between its intermediate growth rate intermediate of nuclear nation right and that's usually where we get the maximum transformation rate this because the transformation rate is a product of growth and creation so here the transformation will be slow because I don't believe much here I want to create a lot with the nuclei kind of growth right so but would you want to have because the transformation is really is the product of growth kind the creation and it basically its best best off you get the highest transformation where nuclear nation and growth rates are intermediate but this is delta T and this is the growth rate and nuclear nation right so that this will be the temperature is that you take joint temperature so no delta T I have very high growth rate this high growth rates yes but a location right because I have no driving force the transformation rate is related to the product of both and so if I make the product of and all g . it's slow here it goes up and then in decreases again because my growth rate this year so this is where I have had a maximum the growth and transformation of transformation much of it in rich and that's basically where I am both nuclear nation and growth are not very extreme but so this information that we have now major transformation fraction is a function of time and I think I have these this kurdish here for many different temperatures and after all this data I can squeeze into a single graft which call the TT taker that is a where we have temperature as a function of time in the green points and far is the points where the transformation starts so why for instance if this is a transformation here at 675 675 misses 1 .period on this graph that's the point where transformations of the Black Point Inn transformation of 15 % right .period is transformation finished yes and if I connect now we all for all the temperature these lingering points I get the green curves which gives me the new tech toys transformation started curve and this is the black 1 is 50 % transport 100 % transfer so you see here is that the maximum transformation rate for perlite formation will be at around 5 15 yes and it'll be extremely rapid the transformation will start within 1 2nd and will be finished within 10 seconds however if I'm very close to this 720 in 7 years since we were 675 the transformation will only start after 20
1:03:26
seconds and will take maybe 500 seconds to finish this and depending on the temperature I get very different transformation however the general rule is submitted general conclusion of this type of studies is that of the a nuclear Asian growth transformation occurs are always see type see type if you close to the transformation of stock in the In this case the effect of temperature the transformation in of the various look at lower temperatures and at the same time it takes longer time to to transform because you have very low growth rates the reason why I have looked office because diffuser fitted variable OK so this is what happens that's a 675 you start transformation from this this 1st in the 1st 20 2nd nothing happens basic depletion of stocks that rose His and eventually everything is paralytic after about 5 minutes there is also 1 thing that happens and I want to mention it here is I'm when you deal with the the transformation and there is also you also change the morphology a little bit Of the perlite as you reduce the temperature Of the transformation of the the perlite is this it's fine the recall the Inter Lamela spacing the letters spacing between the the right like level the the a type what level is decreased In this week of course perlite is called find perlite now what happens now but we do I show you hear that at about 5 50 the transformation fierce very rapid to perlite but what happens if I go below their insights told you just a moment ago .period would still get perlite but it very slowly and that's not really cool because as 1 other thing that happens is as you reduce the temperature the this his Serfaty stocks to to dropped considerably in fact With this 70 of substitution all element yes a becomes close to 0 this substitution all elements are having much lower diffuse 70 then the interstitial why would that be what think about the interstitial elements it sets in interstitial position has and it can hop from 1 injustice position to another a substitution all elements needs to have a vacancy in it's in the neighborhood you need to have an actor who has to be absent from the other lattice was so unique to form 1 of the ought to have the vacancies for diffusion of substitution or this the substitution of the fusion is this very strongly that reduced and you get all the microscopic chips get on the like restriction 1 the MicroStrategy get is is this is the plane the is formed in conditions where there's only only interstitial diffusion 10 no substitution of the few needed my conservative Bloomberg very much finer than than I the perlite is very difficult to see where the carbide essayist department is also there it's also constituents but that's a mixture of variety and a seaman tight yes but it's more than the semen type is extremely small enough to be doesn't have it a Lamela structure and because this is
1:08:45
this is this migrants structure here no I am the 1 of these structures whether it's being or not their eyes not neither 1 is a stable microscope there the stable Mike rastructure is 1 where you would keep the temperature the temperature constant the transformation and wait long enough the the equilibrium like rastructure the lowest energy like restricted to be formed and if you do this and it does take a lot of time when hours at this particular time which you form is what we call Sparrow died so thoroughly and this is the microscope it's actually a farright matrix With the globules little circle where the particles of the semen and reason why and you get transformed these this Lamela structure also all for relying too those Pharoah died it's because it has much less surface antigen and that's that's the reason why we the prolific like structure is a high energy configuration if you want in comparison to the only thing way you have lots of surfaces and lots of interfaces so that's basically the driving force for the formation of this throwing the reduction of the into facial area OK so this a good time to honor to stop 12 15 let's stop here and