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Callister - An introduction - 8th edition

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390 • Chapter 10 / Phase Transformations<br />

Spreadsheet Problem<br />

10.1SS For some phase transformation, given at<br />

least two values of fraction transformation<br />

and their corresponding times, generate a<br />

spreadsheet that will allow the user to determine<br />

the following: (a) the values of n<br />

and k in the Avrami equation, (b) the time<br />

required for the transformation to proceed<br />

to some degree of fraction transformation,<br />

and (c) the fraction transformation after<br />

some specified time has elapsed.<br />

DESIGN PROBLEMS<br />

Continuous Cooling Transformation Diagrams<br />

Mechanical Behavior of Iron–Carbon Alloys<br />

10.D1 Is it possible to produce an iron–carbon alloy<br />

of eutectoid composition that has a<br />

minimum hardness of 90 HRB and a minimum<br />

ductility of 35%RA? If so, describe<br />

the continuous cooling heat treatment to<br />

which the alloy would be subjected to<br />

achieve these properties. If it is not possible,<br />

explain why.<br />

10.D2 Is it possible to produce an iron–carbon<br />

alloy that has a minimum tensile strength of<br />

690 MPa (100,000 psi) and a minimum ductility<br />

of 40%RA? If so, what will be its composition<br />

and microstructure (coarse and<br />

fine pearlites and spheroidite are alternatives)?<br />

If this is not possible, explain why.<br />

10.D3 It is desired to produce an iron–carbon alloy<br />

that has a minimum hardness of 175 HB<br />

and a minimum ductility of 52%RA. Is such<br />

an alloy possible? If so, what will be its composition<br />

and microstructure (coarse and<br />

fine pearlites and spheroidite are alternatives)?<br />

If this is not possible, explain why.<br />

Tempered Martensite<br />

10.D4 (a) For a 1080 steel that has been water<br />

quenched, estimate the tempering time at<br />

425C (800F) to achieve a hardness of 50<br />

HRC.<br />

(b) What will be the tempering time at<br />

315C (600F) necessary to attain the same<br />

hardness?<br />

10.D5 <strong>An</strong> alloy steel (4340) is to be used in an<br />

application requiring a minimum tensile<br />

strength of 1380 MPa (200,000 psi) and a<br />

minimum ductility of 43%RA. Oil<br />

quenching followed by tempering is to be<br />

used. Briefly describe the tempering heat<br />

treatment.<br />

10.D6 Is it possible to produce an oil-quenched<br />

and tempered 4340 steel that has a minimum<br />

yield strength of 1400 MPa (203,000<br />

psi) and a ductility of at least 42%RA? If<br />

this is possible, describe the tempering<br />

heat treatment. If it is not possible, explain<br />

why.

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