some questions related to material sci... plz do answer them as i need them very badly plzzzzzzzz?

Question

1. why is mild steel relatively weak but very ductile?
2. why is 0.8% C steel very strong but much less ductile?
3. why is cast iron brittle, but still very widely usd?
4. why is martensite brittle?
5. why does toughness increases with tempeing time and temperature?
6. is it better to use a slow cooled sample , rather than a quenched plus tempered one?

Answer 1

2-all of the microstructure of it is a structure named Perlit(consists of ferit and cemantite , later is a hard phase) . all of matterial that is very hard they are brittle unless we treat them.3- all of cast iron is not britle we hane ductile cast iron but generally they are britle because of cemantite phase.4- it is very hard then is brittle.5- because when tempering harsness decreases.6- it deponds on final application.1-all of alloys that are weak they are ductile . we need smaller force to reform them.hope they are useful for you.