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카테고리
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학습트랜스크립트
00:00안녕하세요.
00:06We are going to learn about phase diagram chapter 9.
00:14Let's start with something familiar.
00:17I took this picture from the textbook,
00:21the starting picture.
00:24And the water phase diagram.
00:28You already saw this diagram many times.
00:31Phase diagram maps where different phases are stable
00:37as we change the external conditions.
00:40See, we can change the temperature or pressure.
00:44Then the water changes their phase.
00:47We see here solid ice or liquid water or vapor steam.
00:56That typically happens.
01:00Pressure and temperature changes normally.
01:04The lines between these regions are phase boundaries.
01:12At this phase boundaries, what's going to happen?
01:17We see liquid and vapor.
01:21They are in equilibrium.
01:23So we can see both of them.
01:25And it's exactly at the point, the line.
01:28That's like two phases coexist in equilibrium.
01:33And at every pressure about one atmosphere.
01:37See, one atmosphere around here.
01:39I'm sorry.
01:41Ice melts at zero degrees Celsius.
01:45And then boils at 100 degrees Celsius.
01:48So I'm sorry, I didn't make the line correctly.
01:52That's what happens.
01:56So we already know about this, right?
01:59Those are the points where a horizontal line at one atm crosses the solid liquid and liquid vapor boundaries.
02:09All three phases boundaries meet at one special coordinate, like this point called the triple point,
02:17where solid, liquid, and vapor can coexist in a perfect balance.
02:24And I don't know how hard this point could be observed.
02:28So if we can adjust the exact temperature and exact pressure,
02:35then it says, the textbook says,
02:38I've never seen this kind of point by my naked eyes.
02:42So then if we do that, we see solid and liquid and gas all together.
02:51That's quite like the fancy phenomena.
02:56I might look at it, look for it somewhere if it exists in YouTube or something.
03:05I'm sorry, I didn't prepare that.
03:07But if I found one link, then I might share that with you somehow.
03:14Why do we begin this one?
03:19Like a phase diagram.
03:20We know like the ice is changing to water and vapor.
03:24That's the easiest one.
03:26But actually we don't see this kind of thing because it doesn't tell us much about the water itself.
03:33So what's the components?
03:35How much water or how much steam and solid can exist?
03:40So it doesn't give them much information.
03:43So, but like every phase diagram we use later is using the same idea.
03:52Plots showing which phases are stable at which condition.
03:57The water diagram builds like intuition.
04:01So crossing a boundary means, crossing boundary means a phase transformation.
04:08Keep that picture in mind as we switch to compositions, temperature diagrams for alloys.
04:17So let's take a look at this one.
04:26But in the previous slides, I also need to mention that I used a few terms like a phase, right?
04:36A region with uniform structure and chemistry.
04:40And then phase boundary, I mentioned this one.
04:43Two or three phases, I'm sorry, two phases are coexisting in equilibrium and triple point, right?
04:52And that's where we can start with.
04:55And then let's switch from the pressure temperature.
05:00That's what we saw in the phase diagram for water.
05:03And then we will change that to temperature composition one.
05:08So here, the x-axis is composition.
05:14In the previous slide, we saw this one with some sort of temperature and then pressure.
05:22But that has been changed to composition and temperature.
05:28Here, we don't see pressure because normally we believe this occurs at one ATM.
05:39So if that tells about some other pressure, then they normally add some comment on the phase diagram.
05:48It has been done at some specific pressure or something.
05:54So the solubility limit here, we see the solubility limit here.
06:02That means the maximum amount can be dissolved in the liquid by that amount, but by the line.
06:13Otherwise, we see only single solution at a given here, this temperature.
06:25So if we look at this sugar water phase diagram, we can guess how much sugar can be dissolved in water.
06:34It's easy, right?
06:35So here, let's say like solubility depends on what?
06:39Like temperature.
06:40Warmer water, if we increase the temperature, then solubility limit will move to the right side.
06:48That means at this point, we can have only 60% sugar weight percent syrup.
06:55But if we increase the temperature, it goes up to 80% sugar containing syrup.
07:06So that syrup might be sweeter if we increase the temperature.
07:12The other way, if we lower the temperature, some sugar will precipitate.
07:20So we can see some sugar solid one and also liquid phase too.
07:27So this simple picture introduces how temperature and composition together determine the number and type of phase present.
07:39Here it shows exactly what alloys phase diagrams do.
07:45That's what we are going to see.
07:47So here it says like a solution.
07:51We know what solution is.
07:53And then also mixture more than one phase.
07:56We will see how it can be explained.
08:00So here a simple question.
08:02What is the solubility limit for sugar in water at 20 degrees Celsius?
08:06So here 20 degrees Celsius, there's a line here because I don't draw that straight correctly.
08:15So there's some helping line.
08:19At 20 degrees Celsius, we know like a 65% of sugar can be dissolved in water.
08:28So if the composition is slightly over 65%, then that's located here.
08:39That means liquid and solid.
08:41Some sugar will be precipitate.
08:45And if we go down to this 60% or something, that means we see only one syrup solution.
08:54The sweetness might be different.
08:56Here like at 20 degrees Celsius, the fully sweet one has a 65% sugar.
09:03But sometimes that like you can add some small amount of sugar in your coffee or the maximum amount of sugar.
09:13Someone has like a very sweet coffee and somebody has the very low concentration of sugar in it or no sugar at all.
09:25Okay, and then let's move to the next phase.
09:31Components and phases.
09:32Here we learn a few words.
09:34Components.
09:35I already used this word in the previous slide, but let's define the word here.
09:40The elements or compounds which are present in the alloy.
09:45So for example, in this whole chapter, we normally treat the kappa and nickel or silver and silver kappa or some tin.
09:59Those elements are described in this whole slide.
10:03I don't think we will have like aluminum for example.
10:06That's what I think.
10:08But we will see.
10:10So those elements are compounds.
10:15But in the previous slide, maybe sugar and water.
10:19That could be some components.
10:21Here like elements or compounds.
10:25You know the words element.
10:26I mentioned this one.
10:27I defined it before.
10:28So if you know the definition of the elements, that might be very useful for your reference.
10:37If you see something in the periodic table, that's an element.
10:40Right?
10:41You remember that?
10:42So if the aluminum or copper, they are in the periodic table.
10:47So they are elements.
10:48But water or methane, gas, they are not in the periodic table.
10:56They are not elements.
11:00They are compounds.
11:03So they are like components.
11:07And then phases.
11:09The physically and chemically distinct material.
11:12The region that form alpha and beta.
11:16Actually, I don't know who defines this like alpha phase or beta phase.
11:22But normally if we see the phase diagram, far left side, normally defined as alpha phase.
11:31And then right side, in the order alpha, beta.
11:37And then if we have three, there might be some certain rule.
11:42But we don't go like more than alpha, beta or gamma.
11:46And actually, we don't care much about alpha phase or beta phase.
11:52What they are.
11:53We don't care much.
11:55So here, it says this like, oh, here, aluminum, copper.
12:00I'm sorry.
12:01Aluminum, copper.
12:02That's the point.
12:03We are using aluminum.
12:05But in the phase diagram, I don't see aluminum.
12:08Alpha phase, dark phase, beta phase, light phase.
12:18I don't think they defined like alpha phase as a dark phase, beta phase as a light phase.
12:25But accidentally, that's what they see.
12:28They match it somehow.
12:32But that's the one.
12:34So a single phase.
12:38Single phase system is homogeneous.
12:41And same properties throughout the whole thing.
12:44A mixture has more than one phase.
12:47Heterogeneous by nature.
12:49The most engineering alloys are multiphase.
12:54On purpose.
12:55Intentionally.
12:57Because combining phases often gives better strength, ductility, or toughness than any single phase alone.
13:05We will see that the carbon ecosystem sooner or later.
13:14Let's move on.
13:15So effect of temperature and composition.
13:18That's what we saw before.
13:20Alterating the temperature can change number of phases.
13:24Here, we see only one phase liquid or liquid plus the solid sugar.
13:32The solid sugar will precipitate.
13:34Right?
13:35So, but isn't it obvious?
13:37So at specific temperature, we can add the sugar in the liquid.
13:43They will dissolve, dissolve, dissolve, dissolve.
13:46Somehow they might have some certain limit.
13:49And then after that, no more sugar will dissolve in that water.
13:54So we will have solid and liquid.
13:58That's quite obvious.
14:00When we increase the temperature, the water and then the sugar, solid sugar, they might have higher kinetic energy.
14:09And they will have the more kinetic energy moving around inside together.
14:17And then that's why they have the highest solubility.
14:21So it's so obvious.
14:23But that's just the regular phenomena that can be drawn or explained or described in this table with numbers.
14:38Do you remember that?
14:39Like without number, we cannot do any science.
14:43That's not a science.
14:48So that's the heart.
14:50This is the heart of phase diagram.
14:53Changing temperature and then the composition might be changing too.
14:59So these sets moves you around the map and can change how many phases are present.
15:07So, so obvious, right?
15:09We have a composition and then temperature.
15:14So is it difficult?
15:16Like a composition, we choose composition, a certain composition and change the temperature.
15:23Once we have a fixed number for composition and temperature, then we know the phase here.
15:29We can just read that point here, liquid.
15:36So I don't think this is a difficult part for you and me.
15:43So it goes that way.
15:47In alloy diagrams, we will do the same thing.
15:50But this is not an alloy one yet.
15:52So we will go to the alloy part with this simple.
15:57Simple phase diagram.
16:01Just locate your point.
16:03Temperature and composition.
16:05Temperature and composition.
16:07And then see which field that point is in.
16:12And then read.
16:14The phase is written in that area.
16:17How simple it is.
16:20And just read it.
16:23Composition and amounts.
16:25That's it.
16:26Okay, let's move on to the criteria.
16:31I'm sorry.
16:33I didn't know I have this many things in this slide.
16:40So I already mentioned this one many, many times.
16:44Starting from this A, we know the certain amount is dissolved.
16:52That's the syrup here.
16:54And then the extra point will be the solid precipitation.
17:00But if we increase the temperature, they will all dissolve.
17:06Right?
17:07The extra, the sugar will be dissolved into that liquid.
17:12So it will become sweeter.
17:16And then if we add more sugar there.
17:20Then certain amount it will dissolve.
17:23But this amount will stay as a precipitation too.
17:28So two phases.
17:30Okay, let's move on to the criteria for solubility.
17:37I emphasize this nickel copper solution many times.
17:44I don't know if you remember that or not.
17:47But nickel and copper.
17:49We use this term.
17:51We see this nickel and copper.
17:54The rum, what is that?
17:56Like a Hume rotary rule.
17:58The crystal structures are the same.
18:00Electronegativities are almost the same.
18:03And then the atom sizes are almost the same.
18:08So actually they are fully soluble to each other.
18:14So that's very important point.
18:19This is just one of the model, model study elements for the elements.
18:28And then also like a metal alloy system.
18:36So I mentioned that they are like some elements are mutually soluble.
18:43That's nickel and copper in the solid state.
18:47When we normally mention like a solution.
18:52That's I don't know that's only to me or not.
18:58But I just think about some liquid part.
19:04But in solid, that's also can be called as a solution.
19:09So totally soluble in solid state.
19:14But other is not.
19:16Other doesn't go this way.
19:18So if we choose nickel and copper, that's what happened.
19:23But in some other metals, it's not going to happen this way.
19:27So let's start with this nickel and copper.
19:30They have mentioned all of this.
19:35This is quite good system to see solubility for each element.
19:46And simple one.
19:48Right?
19:49So let's move on to this phase diagram for nickel and copper.
19:54So let's start with this figure.
19:59I'm sorry.
20:00So let's start from the first point.
20:03Indicate the basis as a function of T and C and P.
20:07But P is here.
20:09P, one equal ATM always and almost always used.
20:14I like almost doesn't count.
20:17But the one ATM here almost is quite important.
20:22So we believe this occurs at one ATM.
20:27So we don't consider the P.
20:29So we only consider T and C.
20:32That's binary system.
20:37Phase diagram for kappa and nickel system.
20:41That's always given.
20:42Here on the x-axis, it says weight percent of nickel is given.
20:49That means on the other side, like 100% is what?
20:54Like kappa.
20:55So we have 100% of kappa and 0% of nickel.
21:01That's left side.
21:03And then 100% of nickel and 0% of kappa is on the right side.
21:10And also temperature is changing from the 1,000 degree to 1,600 degree Celsius.
21:24But that's not that difficult.
21:30Here we see some phases.
21:35When we increase the temperature, they are all dissolved each other
21:39and then they act as a liquid.
21:42So here liquid.
21:44In solid part, if the temperature is lower than 1100, maybe around here.
21:54See, they are completely dissolving in each other.
21:58So 0% nickel exists.
22:01If we add a small amount of nickel, they dissolve in kappa.
22:06Isn't it weird?
22:08Completely dissolving this way.
22:14We will learn about the words in the next slide.
22:17That's isomorphous.
22:21You know, isomorphous.
22:26I will let you know the word isomorphous in the next slide.
22:32We will have some of the definition for that word.
22:37Here, the two phases, liquid and alpha.
22:42And then there are some words like liquidus or solidus.
22:52This means liquidus means some adjective form of liquid.
23:02Solidus means it's solid-like.
23:05It's also adjective of solid.
23:10It's solid-like and liquid-like.
23:15And that line.
23:16Line is liquidus.
23:18And in Korean word, it's...
23:27I don't know the exact word, but it's like...
23:34The word itself is not that important.
23:55I'm not gonna ask you the meaning of liquidus or solidus.
23:59And if needed, I will give you the line and also name.
24:06But for the communication, I will use this word many times.
24:11So if you understand the word, it might be easier to understand the whole system.
24:20So this green line is liquidus.
24:27Above this liquidus, all liquid.
24:31Below this solidus, they are all solid.
24:35In the solid part, we just saw isomorphous.
24:40Okay, let's move on to the things.
24:43Isomorphous binary phase diagram.
24:46So the word isomorphous, this word is quite important for understanding this whole system.
24:53Isomorphous means they are completely dissolving in the solid form.
24:59That word is only considered in this solid part.
25:05If we go once over this liquid part, normally the liquids are all mixable.
25:17Like gas.
25:18And in the liquid part, we know some liquids are not mixable to each other.
25:24But in the liquid, in the metal alloy, they are normally quite mixable at high temperature.
25:32And also for the gas, they are quite mixable.
25:36So here, in this region, we are saying isomorphous.
25:43They are completely dissolving in each other without considering this amount of nickel.
25:58That would be 0% of nickel and 100% nickel.
26:05So this is the modal system we are learning.
26:08Kappa nickel.
26:09I mentioned like isomorphous.
26:12Completely solid solubility.
26:15That's the kind of definition.
26:18Complete solid solubility.
26:21We don't care much about liquid part, right?
26:24I mentioned that because for the liquid, they are quite actually missable.
26:34Above this liquidus, 100% liquid.
26:38And below the solidus, 100% solid alpha phase.
26:43But what's happening between this solidus and liquidus?
26:48We just read it.
26:50Liquid and alpha phase.
26:53How easy it is.
26:56So that's the one we are going to talk about.
27:03So I don't think that's that much difficult.
27:06So let's see binary system.
27:11Two components, kappa and nickel.
27:14So that's the information we can get from this phase diagram.
27:17Because it says kappa-nickel phase diagram.
27:20We know like two components.
27:22Isomorphous.
27:23Complete solubility of one component in another alpha phase field.
27:28It extends from 0 to 100% nickel.
27:32That's the way.
27:36So let's move on to the next one.
27:39Phase diagram.
27:41Determination of phase present.
27:43So here's the phase diagram.
27:46So we need to get some information from the phase diagram.
27:49That's what we are learning at this moment.
27:52Right?
27:53So rule number one here.
27:56Simplest.
27:58If we know T and C0.
28:02C0.
28:03C0.
28:04Sinat.
28:05Whatever.
28:06So temperature and components.
28:09Then we know what?
28:12Which phase is present.
28:15Or which phases are present.
28:17So let's say 40% of nickel.
28:20Weight percent nickel.
28:22At 1400 degree Celsius.
28:25What phase is existing there?
28:29It says liquid.
28:30Right?
28:32But here in this phase diagram.
28:35We see this green area.
28:38And then this blue area.
28:40But actually.
28:42In real phase diagram.
28:45We don't see this color at all.
28:48If we have this color.
28:51That might be easier to.
28:53See what's existing there.
28:56Um.
28:57Sometimes I see some.
28:59Uh huh.
29:00Lines.
29:01Or.
29:02Dots.
29:03To see the.
29:05If this reason is just one thing.
29:09But we know that.
29:10Like.
29:11Although the liquid is written in this.
29:14Like upper part.
29:15It doesn't meet any line.
29:19Up to this area.
29:21Right?
29:22So wherever I choose the point.
29:25That's all liquid part.
29:27The same way.
29:28Wherever I choose.
29:30These are all alpha phase.
29:32The solid form.
29:34Right?
29:35So it's easy.
29:37A point.
29:39Which is A.
29:41Here A.
29:42Alpha phase.
29:43B.
29:44Liquid plus.
29:45Alpha phase.
29:46And C.
29:47There's no C.
29:48Okay.
29:49That's the thing.
29:50We can learn.
29:51Uh.
29:52There's a rule too.
29:53If we know.
29:54T and C is zero.
29:55Then we can determine.
29:56The composition of each phase.
29:58Okay.
29:59That's the thing.
30:00We can learn.
30:01Uh.
30:02There's a rule too.
30:03If we know.
30:04T and C is zero.
30:05Then we can determine.
30:06The composition of each phase.
30:07That's interesting.
30:08Right?
30:09So let's see.
30:10Um.
30:11The.
30:12How we can do that.
30:13So, uh.
30:14It's obvious to say.
30:15If we have some point here.
30:16Then.
30:17What's the point in that line.
30:18We will see.
30:19On.
30:20This.
30:21Uh.
30:22Cause the C is zero.
30:23At 35%.
30:24At 35%.
30:25At 35%.
30:26At 35%.
30:27At 35%.
30:28At 35%.
30:29At 35%.
30:30At 35%.
30:31At 35%.
30:32At 35%.
30:33At 35%.
30:34At 35%.
30:35At 30.
30:36At 30.
30:37At 30.
30:38And 20.
30:39At 30.
30:40At 30.
30:4120 degrees Celsius.
30:42Only liquid.
30:43Present.
30:44That composition is 35%.
30:46Or something.
30:47And then.
30:48Uh.
30:49TD.
30:5011 to 90 degrees Celsius.
30:51Only alpha phase exists.
30:52Because it says alpha.
30:53And then that composition is 35%.
30:55At 35%.
30:56At 35.
30:57At 30.
30:58At 30.
30:59At 30.
31:00At 30.
31:01At 30.
31:02At 30.
31:03At 30.
31:0435.8% nickel.
31:09That's easy, right?
31:12Do you see any difficulties?
31:15Understand this?
31:17In TB, that's the problem.
31:22We know what kind of phases are existing because it's white region
31:27and then in that white we see liquid and alpha phase.
31:30So liquid and alpha phase are existing.
31:34Right?
31:38And then we have to draw a tie line to see what's existing there.
31:46So if we make this tie line, that is here and then the other one goes here.
31:54I'm sorry, I don't draw the line straight, clearly.
31:59They might have this line.
32:00I'm sorry, I shouldn't draw that one.
32:05So liquid phase should have, because it's mid-air, liquid phase exists there with 32% of nickel.
32:17And then the solid phase has 43% of nickel.
32:22So that's the information we can get all.
32:32Do you need any more information?
32:35Are you interested in something more?
32:38So at point B, we know what's existing.
32:44So I hate myself for this around this line, not straight line.
32:56I think my mind is not that straight.
32:59Okay, curved.
33:01So we know like 32% of liquid and the 43% weight percent of nickel containing alpha phase solid form.
33:13Then if total amount is 100%, what percentage is existing as liquid part, what percentage is existing as like the alpha phase part?
33:31So that's what we are going to learn in the next slide here.
33:35So rule three, that's like some sort of the level rule, rule three brings in the level rule in a two-phase region, two-phase region.
33:52One-phase region is not difficult because we know that points already given, giving some idea about the composition.
34:02But here, at this point, that is not the real composition we are looking at.
34:13So that exists as the tie line, then liquidus line, and then solidus line.
34:20So we just accepted 32% of liquid and 43% of solid.
34:32But we don't know how much of each phase are existing with a specific ratio.
34:43So that's the, if we do that, the level rule, this one exists with this amount, and this one exists as this amount.
35:04That's the other way, that's going to explain in the next slide too.
35:11But if you do not know exactly that point, you can just simply guess.
35:19So here, their state was liquid right before, because it came down only this amount.
35:32It's close to the liquid part yet.
35:36So liquid should be the higher amount than solid form.
35:42So when we lower the temperature, we may expect higher amount of solid, isn't it?
35:49So at higher temperature, we expect more amount of liquid rather than solid.
35:57So liquid should have a higher portion.
36:02The solid should have a lower portion because it's closer to the liquid part.
36:08So if we come down around here, then I'm sorry, I hate myself.
36:15Then at lower temperature, we may expect more amount of solid rather than liquid.
36:26Okay, I hope you understand what I'm talking about.
36:30That's the level rule.
36:32And then this line is called like isotherm, 등운 곡선, because it's the same temperature.
36:41And say like a watt fraction of each phase, it looks like the, or it's a teeter-totter.
36:50So they are balanced, even though it has a smaller weight and a higher weight.
36:57So their ratios are multiplying this way, it goes to this way.
37:06But they didn't explain why this could be accepted for this system.
37:17It's not complete theory part.
37:20And also if their densities are quite different from each other, this rebel rule does not, it
37:27give some hunch or hint, but it doesn't match with like a high accuracy.
37:37So, but for most of the metal, they have like a similar density.
37:43So it might be still accepted for most of the metals.
37:49But if we go like a very detailed one, or if we need a very high accuracy, it's not, it doesn't
37:59go this way clearly.
38:02So whatever.
38:04But if we have a test or exam, and we should go this way, right?
38:10We cannot, you cannot say like a professor said, it's not completely correct all the time.
38:20So we don't, we don't know much about it.
38:25Then you may not know your score.
38:31So here's some calculus way, but we, I just explained the easier way to understand.
38:40Okay, so let's move on to the next slide here.
38:47Cooling the copper nickel alloy.
38:55Let's walk through the microstructural evolution for copper nickel at the composition zero is
39:0235, 35% weight percent nickel during slow cooling.
39:10So equilibrium, it may have time enough to have like equilibrium in the previous solid and
39:19the next solid form.
39:23So let's move on to B.
39:25And then nickel, the alpha phase, the solid may start to form.
39:34And then the next slide C, then it grows alpha phase, the 36% weight percent nickel and 43% of nickel.
39:47See, this is quite important point.
39:51At the very beginning, higher temperature, the seeding nickel was like a 46% of nickel.
40:01When we lower the temperature, then that should move to 43% of nickel.
40:08See, it's moving.
40:13So to dilute from 46 to 43, we need some time.
40:22So that equilibrium time is required.
40:25That's why it says like a slow cooling.
40:28I just saw somewhere in slow cooling.
40:35Maybe textbook.
40:37Okay, so it works only for slow cooling.
40:41The next slide will talk about some fast cooling.
40:46So theoretically, the ratio, the weight percent has been changing 46% to 43%.
41:01And then if we go to the next one, D, C, like a 36% nickel.
41:11So that means like a 64% is copper, right?
41:16So they are changing their composition is changing.
41:23Finally, that should be 35%, right?
41:27Because it follows the straight line to 35%.
41:32So E, that's 35% of the nickel, the whole thing.
41:41That's for slow cooling.
41:44The whole inside is now 36%.
41:48The starting point was 46%, right?
41:51So you have to keep in mind that way.
41:55And then let's move into this cold equilibrium structure.
42:02Let's compare, oh, here, slow rate of cooling.
42:08Equilibrium occurs.
42:10And then on the right side, I see the inside of 46%.
42:16And then later here, that's 35%, even or less than that,
42:21because the higher concentration was captured inside.
42:26So the outside could be lower concentration.
42:30So if we want to make this graded nano core, then we have to cool it in very fast mode.
42:46So if you need a very high quality, evenly distributed nanostructure or metallic compound,
42:56you need some time to make some equilibrium between them.
43:02So this is quite important to obtain the special characteristics for the specific metal.
43:14So the change in the temperature and with the specific weight, that's very important to make the same kind of samples for the metal alloy.
43:29So here, I mentioned that like this composition affects the properties through solid solution strengthening.
43:50So adding the solid atom into this lattice strain, that's what we learned in the previous chapters a long time ago.
44:00So the lattice strain and then impedes the dislocation motion too.
44:05In copper nickel, tensile strength typically rises from the pure metals and then rises up to some point and then decreases.
44:18That maximum occurs at around 60%.
44:23And ductility, that's a different way.
44:28It usually drops to a minimum near that intermediate composition.
44:34So there is a strength-ductility trade-off.
44:38If something is greater and the other goes down, this trend is clean and predictable.
44:46Handy for tailoring properties with composition alone.
44:51Okay.
44:52Let's move to the next slide.
44:58That's like a binary, two components.
45:01And ductility has a special composition with a minimum melting temperature.
45:06So we have a weird phase diagram that's totally different from the previous slide.
45:16So it's like a jump to the quite difficult phase diagram.
45:23But if you understand this phase diagram, you will understand most of the phase diagram.
45:29It says like a kappa and silver system.
45:36So let's start from the beginning.
45:43So here, what do we see?
45:46Like alpha phase, beta phase, and liquid phase, and liquid plus alpha, or liquid plus beta, or alpha plus beta.
45:57So that's the reason.
46:01And here also, horizontal eutectic idle thumb.
46:06Eutectic idle thumb, that's 779 degrees Celsius.
46:11And the composition CE, eutectic composition is 71.9%.
46:20So we will see what's happening in this point.
46:24But in the previous slide, we saw like some sort of this one, right?
46:32The liquid plus some solid phase.
46:37So when we increase the temperature, normally the solubility is also increasing.
46:44That's what we saw a little bit.
46:47But here, when we increase the temperature, that it's decreasing and then increasing.
46:59I'm sorry, like this is the temperature.
47:02So when we lower the temperature, then it's moving this way.
47:08At a certain point, it touches the bottom.
47:13That's eutectic point.
47:15Eutectic stretch is typically lamella.
47:20Alternating layers of alpha phase and beta phase.
47:25They are alternating.
47:28Because short diffusion length minimizes the time and the energy during cooperative growth.
47:37That's what textbook mentions.
47:40So the same way.
47:44Like we have certain the composition and then temperature.
47:50We know the phase is alpha plus beta.
47:54Then alpha phase here.
47:56Alpha phase composition and beta phase composition.
48:00That's the ratio.
48:02So beta might be this ratio and alpha phase is this ratio.
48:07So that's the way we see.
48:12So from this phase diagram, let's see what we can get.
48:16Like three single phase regions.
48:18Liquid, alpha, and beta.
48:21Single phase.
48:22And then limited solubility, alpha.
48:25Mostly kappa.
48:27Here it's kappa-silver.
48:31So this is the silver part.
48:34And this is the kappa hundred percent.
48:38And then zero percent.
48:40So alpha phase means here.
48:42Most of the alpha phase has a higher concentration of kappa.
48:48And beta phase has a higher portion of silver part.
48:54Then no liquid below eutectic point.
48:58We don't see liquid.
49:01And composition at temperature.
49:03Te.
49:04That's like a eutectic composition.
49:11Eutectic reaction.
49:16Liquid becomes the alpha phase and beta phase.
49:19So it's not, it doesn't have like two phases.
49:27They have alpha and two phases.
49:30It has two phases, alpha and beta.
49:32It doesn't have liquid part.
49:34Let's see.
49:35That's the point.
49:36And then let's see what we should know.
49:47This is like a tin and the PV.
49:51LED.
49:52The system.
49:53That alloys at a hundred and fifty degrees Celsius.
49:58Determine the C.
50:03Forty percent.
50:06Tin.
50:07Forty percent.
50:08This is tin, right?
50:10So forty percent here.
50:12I'm sorry.
50:13Tin.
50:14Sixty percent.
50:15Red.
50:16So here hundred percent of red.
50:17Zero percent of red.
50:18Pe.
50:19So we can just simply.
50:20Here.
50:21Hundred and fifty degree Celsius.
50:22Base.
50:23It says alpha and beta, right?
50:25Alpha and beta.
50:26And then the.
50:27That's eleven percent.
50:28Like the.
50:29The alpha phase.
50:30Should have like a.
50:31Eleven percent of tin.
50:32Because it says.
50:33This is the tin.
50:34The tin.
50:35This is the tin.
50:36The tin.
50:37So we can just simply.
50:38Here.
50:39One hundred and fifty degree Celsius.
50:40Phase.
50:41It says alpha and beta.
50:42Right?
50:43Alpha and beta.
50:44And then the.
50:45That's eleven percent.
50:46Like the.
50:47The alpha phase.
50:50Should have like a.
50:52Eleven percent of tin.
50:54Because it says.
50:55This is the tin.
50:56That portion.
50:57And.
50:58The other way.
50:59Eighty-nine percent.
51:00Of.
51:01The.
51:02The.
51:03Lead.
51:04And.
51:05Then.
51:06The.
51:07This side.
51:08Ninety-nine percent.
51:10The tin.
51:11One percent.
51:12Of.
51:13The.
51:14This.
51:15Lead.
51:16And.
51:17The relative amount.
51:18This way.
51:19This way.
51:20Can do the same thing.
51:22And.
51:23Also.
51:24Determine.
51:25The.
51:26Phase.
51:27Two hundred and twenty.
51:28See.
51:29So.
51:34Existing.
51:35This way.
51:36And.
51:37This way.
51:38But.
51:39That's.
51:40The.
51:41Relative amount.
51:42The same thing.
51:43Right?
51:44This ratio.
51:45And.
51:46This ratio.
51:47That's easy.
51:48That's it.
51:49I.
51:50I don't think.
51:51It's.
51:52It's difficult.
51:53To understand.
51:54So far.
51:55So.
51:56The.
51:57This might be enough.
51:58For.
51:59Our understanding.
52:00If we.
52:01If we.
52:02If we.
52:03Go.
52:04To the practice test.
52:05There might be.
52:06Very complicated.
52:07Questions too.
52:08But.
52:09I'm not going to give you.
52:10That.
52:11Hard questions.
52:12For the exam.
52:13You don't worry about it.
52:14So.
52:15This might be.
52:16Everything.
52:17You.
52:18Have to understand.
52:21For.
52:22Your.
52:23Future reference.
52:24And.
52:25Then.
52:26Also.
52:27Like.
52:28For.
52:29Your.
52:30Final exam.
52:31Or.
52:32Any.
52:33Exam.
52:34Preparation.
52:35Thank you.
추천
32:06
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다음 순서
1:03:42
45:38
27:57
20:43
21:57
48:13
43:07
32:58
46:48
21:20
40:13
47:27
33:04
38:05
49:26
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