Question 5 (a)(i) What theories of failure are used for? Ductile of materials and Brittle of materials? (2marks)
(ii) List at least two factors that promote the transition from ductile to brittle fracture? (2marks)
(iii) Often, it is beneficial to know how many materials or components can be combined without producing an additional phase. When alloying elements are added to metal, solid or liquid solutions can be formed. For example, when we add sugar to water, sugar solution is obtained. When we diffuse a small number of phosphorus (P) atoms into single crystal silicon (Si), we produce a solid solution of P in Si. Furthermore, they display unlimited solubility. Regardless of the ratio of water and sugar, only one phase is produced when they are mixed together. What factors or conditions that must be satisfied before a single phase of solution are realized? (4marks)
(b) .What is a eutectic phase diagram? Draw a typical equilibrium diagram for a eutectic type of a system with limited solid solubility and explain its important features.
please answer all.clearly written.thank you.
i) Theories of failure used for ductile and brittle materials:
For Ductile materials, the failure mainly happens due to the shear stress (which is the main root cause for the yielding in ductile materials). The max shear stress criteria or Tresca criteria is used for a ductile material. Because in ductile the failure happens in the plane where the max shear stress acting effectively and Von mises criteria also used for these materials but the Tresca criteria is more simple compared to Von mises criteria.
Tresca Criteria: Yielding occurs when the difference between the maximum and minimum normal stresses reaches a critical value or Yielding occurs when the maximum shear stress reaches a critical value.
(or)
iii) Hume Rothery Rules:
A solid solution is a phase where two or more elements are completely soluble in each other. There are two types of solid solutions 1) Substitutional solid solutions 2) Interstitial solid solutions.
There are rules which govern the formation of solid solutions:
b) Eutectic Diagram:
Eutectic diagram, it mainly represents a eutectic reaction where liquid phase can split into two solid phases.
(L-->+
).
And the above diagram represents the limited solid solubility on
both sides (A-Side and B-side), due to this limited solid
solubility two solubility lines formed which represents the maximum
amount of solute in solid solution at that particular temperature.
(The lines surrounded both alpha and Beta phases below eutectic
temperature are called as solvus lines which represent the
solubility limits at all the temperatures ).
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