Question

please answer question 2,3,4

A critical feature of steel is that a considerable amount of carbon can be dissolved in the austenite, phase, (up to 2.14 w/o at 1147"C), whereas carbon is essentially insoluble in ferrite, Cooling from point d to e, just above the eutectoid but still in the an increased fraction of the +y region, will produce phase and a microstructure similar to that shown: the particles precinitates out in the form af an intermetallic.compound called iron-carbide with the atomic formula Fe C. Carbide precipitates can be controlled so as to impart very high strength to the alloy by impeding the motion of crystal dislocations. determined by constructing a tie line at the temperature T the a phase will contain 0.022 wt% C, while the y phase will be of the eutectoid composition, 0.76 wt% C. As the temperature is lowered just below the eutectoid, to point f, all they phase that was present at temperature When carbon is dissolved in the austenite at high temperature and the alloy is allowed to (and having the eutectoid composition) will transform to pearlite by decomposes into ferrite and carbide Before the eutertoid temperature is reached either the to nearlite and when it does so it will have shifted to the eutectoid composition prior to the ferrite phase, or the carbide phase, will precipitate out, depending on the alloy composition. If transformation occurring. That it why when we wish to estimate the amount of pearlite that reaction temperature is reached, whereas for carbon contents greater than this, Fe:C will precipitate out first. Steels are thus classified into 3 basic classes: hypoeutectoid (w/o C<.76 % ) , eutectoid (w/o heains, We do this by applvine the lever rule at a temperature iust above the eutectoid. Eutectoid steel: bputectoid tune hecause ary bigh carbon steels lack toughnass The art of steelmaking is largely one of manipulating microstructure (i.e., the shape and distribution of the carbide phase) by thermomechanical treatment. LL Schonatik artre ser of ee P and buloe de eascesd Hypo-Eutectoid Steel: Consider a hypoeutectoid steel (W/o c.76 % ). Cooling an alloy represented by moving down the vertical line yy' in Figure (i. At about 875 C, point c, the microstructure w consist entirely of grains of the Austenite phase, as shown schematicaly in of this composition is phases will coexist along the original s in the schematic microstructure. Most of the small particles will form andy phases may be these compositions correspond, respectively, to grain boundaries. The compositions of both lir about 0.020 and 0.40 wkpriate tie 20 pm While cooling an alloy through the a phase region, the composition of the ferrite phase changes with temperature along the a (ay) phase boundary, line MN, becoming Sgnuy n aon. other hand, the change in the comp austenite is y) y boundars Fig (i Fig (ii) Eutectoid steel Let's consider eutectoid steel (0.76 wt% C , Fig (ii)) as it is cooled from a pure Austenite region, beginning at say 800C (point 'a h mcrotrcture woula .consist or a singie pnase, le, austet. AS the alay s cooled, temperature (727 C), thermodynamIcally unstable and decomposes into- the temperature is reduced. Fig(ii) and moving down the vertical line x-x. At Upon crossing eute becomes austenite (or known as carbide). This lamellar structure is called Pearlite because of the diffraction effect of t erascopc plates dreates clors that look ke Fate a) corresponding microstructure is shown in Fig. (ii The relative amount of Ferrite and Cementite Ausi feri Fembe(al Cowth daectke found by applying Lever rule just below the eutectoid temperature. of perite elte Caten dttr Ferrite (the a phase) and iron carbide (Fe,C) Microstructure of 0.38%Cs ing Proeutectoid Ferrite Figl- Hypo eutectoid Steel eformation in this.case the relative laver thickness is approx is NOT photomicrograph of eutectoid steel showing the Pearlite, P imately 8 to 1. Figure (iv) is a phase, but rather it
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Answer 1

utactad tomp 27c A O02 Fe 6.67/ laver sule along Apply the line ABc B C amount of Fernite (ad) A C ferrita 6.6 - 0.76 X 100 6.670.025 5.91 ferrita X (00 6.645 88.93% y offerrita 11-6//% ofCementile (Fe3c

eutectord point 0.761-C 0s4. C For hypo eutactoid Compost whou .C Apply lever gula along the dina Ae mount otm eutactoi d eute proeutictod B C チferi te A C 06-0.4 x l00 0,T6 0.025 0.36 xle0 ApToeutactoid ferrita 0.489 26 5/ tearhte 00-73.5

ulactord A- 0.4.C beroucte Amount CO fernite 100 - A C 6.6-0.4 6.69 0.025 94.36/ of-tente l00 4 36/ Gamentete -641- amentate

Eutactoid Fe 0-167C Fesc Pply tever suule almg the lona AB C ga AB (D pro eutactoid Camentita AC 1«2-0276 -xloo pro eutactaid amateta 6+6-076 0.094X10D 7.41. pro eutactsi Gamanlt

BC K IOD A C 6-67-12 X l00 6-67-076 pealate "/ss.tb 6.69/C 1-2C Laver sule alom Arply the lina ABD %oferrite X LOO A C 6--67-1-2 6.67-0.02 fernta 82.32y

amento te AD AC 2-0.02 6.67-0.025 ament ta