1.(a) Briefly describe the microstructural difference betweenspheroidite and tempered martensite.
(b) Explain why tempere dmartensite is much harder and stronger.
2.Rank the following iron–carbon alloys and associated micro structures from the hardest to the softest: (a) 0.25 wt% Cwith coarse pearlite, (b) 0.80 wt% C with spheroidite, (c) 0.25 wt%C with spheroidite, and (d) 0.80 wt% C with fine pearlite. Justifythis ranking.
3.Briefly explain why fine pearlite is harder and stronger than coarse pearlite, which in turn is harder and stronger than spheroidite.
4.Briefly describe the simplestcontinuous cooling heat treatment procedure that would be used inconverting a 4340 steel from one microstructure to another.
(a) (Martensite + ferrite + bainite) to (martensite + ferrite +pearlite + bainite)
(b) (Martensite + ferrite + bainite) to spheroidite
(c) (Martensite + bainite + ferrite) to temperedmartensite
5.Briefly describe the simplest heat treatment procedure thatwould be used in converting a 0.76 wt% C steel from onemicrostructure to the other, as follows:
(a) Martensite to spheroidite
(b) Spheroidite to martensite
(c) Bainite to pearlite
(d) Pearlite to bainite
(e) Spheroidite to pearlite