Q1. Chapter 8/9: Failure/Phase Diagram (20%) (i) Please circle the hardest and most brittle microstructure of steel from the following choices. (a) Spheroidite (b) Coarse Pearlite (c) Fine Pearlite (d) Bainite (e) Martensite (ii) In the making of a traditional samurai sword, both hardness and flexibility/ductility need to be taken into consideration. The judicious combination of which two microstructures of steel will confer both hardness and ductility? (iii) Name the two signature marks on a piece of metal that has been cycled to failure. (iv) The figure on the right shows a piece of steel recovered from Titanic. Name the microstructure indicated by the arrow. Solution 1) Martensite Explanation - When austenite is cooled at higher rate , such as by quenching it in water , its Face centered cubic (FCC) structure is transform to a Body-centered tetragonal (bct). this microstructure is call martensite. Because martensite does not have as many slip svstems as Body centered cubic (BCC) structure it is extremely hard and brittle. 2)The judicious combination of ferrite and martensite structure of steel confer both hardness and ductility Explanation- Martensite is hardest structure (Refer Answer 1) and ferrite is ductile structure as it contain very less persentage of carbon. Combining this two structure Dual phase steel is produce which has both hardness and ductility. NOTE- You are not allowed to post multiple questions in one..

1. Q1. Chapter 8/9: Failure/Phase Diagram (20%) (i) Please circle the hardest and most brittle
microstructure of steel from the following choices. (a) Spheroidite (b) Coarse Pearlite (c) Fine
Pearlite (d) Bainite (e) Martensite (ii) In the making of a traditional samurai sword, both
hardness and flexibility/ductility need to be taken into consideration. The judicious combination
of which two microstructures of steel will confer both hardness and ductility? (iii) Name the two
signature marks on a piece of metal that has been cycled to failure. (iv) The figure on the right
shows a piece of steel recovered from Titanic. Name the microstructure indicated by the arrow.
Solution
1) Martensite
Explanation - When austenite is cooled at higher rate , such as by quenching it in water , its Face
centered cubic (FCC) structure is transform to a Body-centered tetragonal (bct). this
microstructure is call martensite. Because martensite does not have as many slip svstems as
Body centered cubic (BCC) structure it is extremely hard and brittle.
2)The judicious combination of ferrite and martensite structure of steel confer both hardness and
ductility
Explanation- Martensite is hardest structure (Refer Answer 1) and ferrite is ductile structure as it
contain very less persentage of carbon. Combining this two structure Dual phase steel is produce
which has both hardness and ductility.
NOTE- You are not allowed to post multiple questions in one.