Please answer all questions very urgent!!! Many thanks a) Describe the four main dislocation types and how they relate t

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Please answer all questions very urgent!!! Many
thanks
a) Describe the four main dislocation types and how they relate
to shear stress and the Burgers’ Vector. [6 marks]
b) How does the yield strength of a polycrystalline material
improve when strengthening mechanisms are employed? Provide your
answer in terms of dislocation movement and interaction. [4
marks]
c) Describe the relationship between yield strength and grain
size, commenting on how dislocation theory is related to this.
Describe the limitations of this relationship.