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# 8.6: Questions

## Quick questions

You should be able to answer these questions without too much difficulty after studying this TLP. If not, then you should go through it again!

1. Where α and β are solid phases, which of the following describes a eutectic transformation?
 a $$\alpha + liquid \rightarrow \beta$$ b $$\alpha \rightarrow \beta$$ c $$liquid \rightarrow \beta + \alpha$$ d $$liquid \rightarrow \beta + alpha$$
Answer

C
The eutectic transformation is from a single liquid phase to two solid phases. Eutectic composition alloys are often used in solders, for example Bi 44wt.%Sn – see the phase diagram

Where α and β are solid phases, which of the following describes a peritectic transformation?

 a $$\alpha + liquid \rightarrow \beta$$ b $$\alpha \rightarrow \beta$$ c $$liquid \rightarrow \beta + \alpha$$ d $$liquid \rightarrow \beta + alpha$$
Answer

A

Which of the following alloying additions stabilises the austenite phase of steel? (You may select more than one)

1. Carbon - C
2. Nickel - Ni
3. Cerium - Ce
4. Silicon - Si
Answer

The answers is a. and b. Carbon, Nickel and Manganese (Mn) are γ - stabilisers.

What differences in appearance might you expect between annealing and deformation twins?

 a Annealing twins are smaller than deformation twins b Deformation twins are smaller than annealing twins c Deformation twins have flat sides, annealing twins are lens-shaped d Annealing twins have flat sides, deformation twins are lens-shaped e There are no differences
Answer

D

Why is spheroidal cast iron tougher than grey cast iron?

Answer

The graphite phase in grey cast iron grows in flake-like shapes, resulting in an interconnected network of graphite. These flakes act as stress concentrators leading to poor toughness. The graphite phase in spheroidal cast iron grows in small spheres, the absence of flakes increases toughness

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