Eutectic, hypoeutectic and hypereutectic alloys

[@gospelmambwe6189]

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[@abhijeet.buet19]

I am a student of Bangladesh University of Engineering & Technology. You are really a great teacher !!

[@deepakmewada8829]

Great expalantion i was studing from gate notes but cant understand the lever rule but u made it happen THANK U SIR JI

[@anurag7058]

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[@studywithmotivation05]

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[@ridhamshah3294]

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[@gianlucacastro5281]

You made me finally understand it. I can't thank you enough!!

[@phivosaslanis2608]

Very good video. Thank you for the video professor. Though, i would like to add that during extreme low cooling in order to theoretecally achieve thermal equillibrium, below the eutectic temperature and close to the left of the diagram (low B concetration), it is possible to have also a phase β percipitation from α phase, due to the solubility limit decrease with temperature decrease. So in total there will be α (proeutectic) + α + β (eutectic) + β (precipitated)

[@rajeshprasadlectures]

You have raised an interesting point that I missed discussing. If the composition of the alloy is less than the composition of alpha in the eutectic, (18% Sn in the case of the Pb-Sn example) then on cooling the alloy will never cross the eutectic horizontal and so there will be no eutectic microconstituent in the microstructure. We will simply get an alpha phase below the solidus which will precipitate beta below the solvus. Thus the final microstructure will be simply alpha (matrix) + beta (ppt). But this mixture of alpha and beta will not be called a eutectic mixture. Also, alpha present will not be called proeutectic alpha because no eutectic formed in this case.

[@phivosaslanis2608]

@@rajeshprasadlectures This point was indeed not mentioned in the video. Though, i was not refering to this case of solidified microstracture. I was refering to the point, just between the two final microstractures mentioned in the video and in your comment for the Pb-Sn example (1st the one that contains alpha(proeutecti)+alpha(eutectic)+beta(eutectic) and the 2nd alpha (matrix) + beta (ppt)). So there is a third scenario that seems to be a microstracture of alpha(proeutectic)+alpha(eutectic)+beta(eutectic) + beta(precipitated). The composition that pushes the creation of such microstracture in your Pb-Sn example is for over than 18% of Sn but close to 18%. As the composition is moving to the right (meaning more than 18% of Sn) the observation of beta (precipitation) decreases. All above can be visualized in the linked image: www.tec-science.com/wp-content/uploads/2021/02/en-limited-solubility-microstructure-diagram.jpg The beta(precipitation) in this case is coming from B atoms diffusion from alpha solid solutions due to solubility decrease with temperature decrease.

[@rajeshprasadlectures]

@@phivosaslanis2608 I am unable to see the third scenario where the beta precipitate occurs along with the eutectic mixture.

[@phivosaslanis2608]

@@rajeshprasadlectures I am sorry for the late response. You just have to click to the following link in order to see the image of the phase diagram i am talking about. This is the link: "www.tec-science.com/wp-content/uploads/2021/02/en-limited-solubility-microstructure-diagram.jpg"

[@nonamechannel5915]

Couldn’t have asked for a better explanation thanks

[@joshebramjoseph2954]

@24:72 this fraction is valid only at that particular temperature right .i.e, the lever should be made corresponding to the equilibrium temperature in question right?

[@himanshushekhar4524]

I wish !!! I could get this video in my b.tech.

[@mr.chindo8570]

Can any one tell me why the tie line for f(proeutectic alpha) (at 19:00) was taken just above Te? As proeutectic alpha forms below Te!

[@Da_Shark]

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[@confetti8003]

Thank you for the explanation! I have a question though - for the last section, where we see the proportion of alpha and beta using the tie line - that is for 183 degrees only, right?

[@introductiontomaterialsscience]

This is almost right but not exactly right. The horizontal line at 183 C is the eutectic horizontal, not a tie line. Tie lines can be drawn only in two-phase regions. At the eutectic temperature of 183 C we have three phases in equilibrium. So when we wish to draw the tie line for total alpha and beta we draw a tie-line in the two phase region lying below the eutectic horizontal, i.e. below 183 C. This can be any temperature below 183 C, but in this example we have taken the temperature to be as close to 183 C as possible so that we can use the compositions of the two end points of the eutectic horizontal also as the approximate compositions of the end points of our tie line. So our calculation is for a temperature just below 183C and not exactly 183 C.

[@confetti8003]

@@introductiontomaterialsscience thank you so much, that really clears up my doubts.

[@monishreddy1797]

Sir..Consider we have taken a *closed system* of the Sn-Pb mixture with 40% Sn..and we are cooling the system with an external source how come the proposition of Sn and Pb change in the process..in the lecture you mentioned that for hypoeutectoid mixture when cooled from liquidus boundary the composition of liquid follows along the liquidus line( 10:58 )..Doesn't that mean the composition of Sn and Pb is changing in the process..Please correct mewhere i was going wrong..also at 10:54 the liquid composition is 100% right

[@introductiontomaterialsscience]

Overall amount of Sb and Sn is not changing. But the system consists of two phases: say, liquid and solid. Both the proportion of liquid and solid in the system and the composition of Sb and Sn in the solid and liquid phases can change without changing the overall amount of Sb and Sn.

[@timelesstunes7507]

wonderful!!! :)

[@vedparulekar478]

So sir, for any composition less than the eutectic composition and temperature less than the eutectic isotherm, will the amount of primary alpha and eutectic will remain the same as that on the solidus line( which you calculated in this video)?

[@srija1410]

What are exactly alpha and beta?They both are solids. then, why should we differentiate them?

[@introductiontomaterialsscience]

We distinguish them on the basis of their crystal structure. Solids of different crystal structure are considered to be different phases. In the Pb-Sn example alpha is Pb rich CCP phase where as beta is Sn rich Body-centred tetragonal phase.

[@srija1410]

Thank you sir

[@azubuikeokechukwu2783]

thanks sir, great explanations

[@yousifameen3607]

Professo, I think the fraction lever should be 40-18/62-18 (19:11)

[@raeesshaikh3430]

No ,he is right

[@abhiseknayak6063]

brother you are wrong to know this concept first go for lever rule 😇

[@rohithmalla9534]

Can the sodification can be taken place in any direction or any particular direction

[@ajinantony755]

hello professor i have a one question, to find fraction of proeutectic we take a tie line above eutectic temperature during that time how will the microstructure consists of eutectic mixture since that portion is liquid + alpha. Also if some one knows please comment.

[@introductiontomaterialsscience]

Above the eutecTOID (not eutecTIC) temperature we have alpha and gamma (not liquid,). So the fraction we get is the fraction of alpha in alpha +gamma mixture. But below the eutectoid temperature the alpha remains unchanged but gamma changes to pearlite (alpha + cementite). The original alpha formed above the eutectoid temperature is now called the proeutectoid alpha. So the fraction of alpha in alpha + gamma mixture above the eutectoid temperature now represents the fraction of proeutectois alpha in the alpha + pearlite mixture.

[@raju_bugude]

sir , you written proportion of eutectic mixture just above the tie line but it actually L+ALPHA

[@abhinababanerjee683]

Sir, in hypoeutectic alloy system, during solidification, will there be precipitate formation of β in the already solidified proeutectic α during solidification below the eutectic temperature? In some books, in the final microstructure in hypoeutectic alloy, β precipitate is shown in the proeutectic α phase.

[@introductiontomaterialsscience]

Depends upon whether the amount of alpha or beta phase increases as we decrease the temperature. If beta phase increases then some of the alpha phase has to convert to beta, This can happen either by transformation of proeutectic alpha or the eutectic alpha.

[@abhinababanerjee683]

@@introductiontomaterialsscience Thank you Sir, I understood the concept.

[@jagadeeshgurana4490]

@@introductiontomaterialsscience sir, with reference to your explanation, how can already formed(solidified) 'pro eutectic alpha' convert into beta phase? Can it still become liquid and convert?(below it's melting point). I just wonder if that could happen . Thanks a lot for your time and patience sir

[@rajeshprasadlectures]

@@jagadeeshgurana4490 It does not have to melt. Transformations can take place in solid state also.

[@bs143]

it was said alpha+beta as mixture of phases. Is proeutectic alpha and alpha in (alpha+beta) are different phases? as phase is chemically homogeneous ,physically distinct and mechanically separable, does proeutectic alpha and alpha satisfy those?

[@introductiontomaterialsscience]

Proeutectic alpha and alpha in the eutectic mixture is the same phase. Only their formation history and distribution in the microstructure is different.

[@LORRY_DRIV3R]

sir what happened to your left hand finger...🥺🥺🥺bandage..??

[@minturaikkonen6149]

You didn't tell about hypereutectic diagram

[@9250925642]

It will be similar to hypoeutectic jus with proeutectic beta phase.

[@jagadeeshgurana4490]

@@9250925642 in hyper eutectic mixture, does the pro eutectic beta forms circles just like alpha, or it's crystal structure looks different?

[@musthakahamed7059]

Sir In just above the eutectic tempertaure, We find the Proeutectic and from that we find eutectic mixture, Then what about the Liquid part in that. Does anyone knows the answer explain to me

[@introductiontomaterialsscience]

Just about the eutectic temperature you have liquid of eutectic composition and the proeutectic phase. Upon cooling through the eutectic temperature it is the liquid phase that transforms to the eutectic mixture. The proeutectic phase remains as it is. So the final microstructure becomes proeutectic phase and the eutectic mixture.

[@mihirthakkar7516]

Anyone downloaded transcript of video form notel website?... previously it was available..now there is no option

[@diwakarP02]

Sir in eutectic alloy(62 wt %Sn in Pb-Sn) what will be the f alpha ? May it around 0.44?

[@SaiRam-vp8yn]

Sir i have this doubt in my mind from very long time.. exactly on the eutectic temperature line @183 degree celsius and also between 18 % Sn and 62%Sn..do we find pro eutectic alpha + liquid+ eutectic mixture (alpha + beta) co-existing?

[@introductiontomaterialsscience]

As the alloy of a hypoeutectic composition hits the eutectic temperature upon cooling it already has proeutectic alpha and liquid of eutectic composition. Call this time, t=0. As time progresses, t>0, the eutectic liquid will start to transform into eutectic alpha and eutectic beta. But all liquid will not transform instantaneously. It will take time, let say the t=tf to complete the transformation of eutectic liquid into an eutectic mixture of alpha and beta. Thus for all times tf>t>0 you will have proeutectic alpha, eutectic mixture of alpha and beta, and eutectic liquid which is yet to transform. The proportion of these phases will be a function of time and thus cannot be calculated using Lever rule.

[@SaiRam-vp8yn]

@@introductiontomaterialsscience thank you so much sir for the explanation

[@PALLavi-v7l]

notes?

[@keval1282]

sir, Why cast iron is harder than mild steel ?

[@IITian_shubham_shekhar_rajput]

Sir, Since lever rule suggests that if you go further down (cooling below eutectic temp and entering alpha and beta phase)total amt of alpha and beta will keep changing as temp decreases?? What does this mean physically? Are atoms from one phase going into another phase,ir smthnng?? Plz help 🙏

[@introductiontomaterialsscience]

Yes. All changes happen due to movement and rearrangement of atoms.

[@IITian_shubham_shekhar_rajput]

@@introductiontomaterialsscience yes sir...in the follow up lectures you have address this in detail.🙏

[@jerrivaishnavi5588]

sir, cooling down the alloy at 40 or 80 % Is explained well. but how does the phase change happen at 18 % Sn. lets say 15 % Sn. then from L+ alpha to alpha area the whole composition is solidified and alpha phase is formed. what happens next when the solidified alpha phase enters alpha +beta phase? great explanation sir and thank you for the responses

[@rajeshprasadlectures]

If the alloy is in the single-phase alpha region and then crosses the solvus line to form alpha + beta then we say that beta brecipates in alpha, This kind of precipitation is used in Al-Alloys to increase its strength. It is called precipitation hardening or age hardening: kzbin.info/www/bejne/jpDUoYiIebOcocU

[@srinivasan3463]

Sir, in Beta region also there might be some alpha and that alpha is the eutectic alpha. Is it correct sir?

[@srinivasan3463]

In diagram, 19.07 I think the fraction of lever should be in the left side of the alpha.

[@gideonjayanth7571]

In the earlier video he told us opposite arm/total arm so for alpha hes doing it right i think

[@bhaskarmahanthi6868]

sir i have doubt on ectectiod and pertectiod

[@introductiontomaterialsscience]

Please ask your doubt.

[@bhaskarmahanthi6868]

@@introductiontomaterialsscience sir i mean i not found any related video about this. Meanwhile tnq for rply sir

[@introductiontomaterialsscience]

@@bhaskarmahanthi6868 Please check the playlist which has an organised list of topics.

[@bhaskarmahanthi6868]

@@introductiontomaterialsscienceokay sir

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[@alokguptamnnit]

Thank you sir❤

[@ansonchin3271]

bravo

[@GauravKumar-np2qm]

Sir what about hypereutectic , you didn't tell

[@jitmohandas9248]

Thanks sir..

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