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The effect of grain size on the fatigue strength is predominant in material with high stacking fault energy while the effect of grain size is negligible in low stacking fault energy material.

Correct Answer: False
The low stacking fault energy material does not form cell structure on deformation, so the crack boundary acts as the source to impede the crack growth, hence the fatigue strength depends upon the grain size. The inverse of this is that the material with high stacking fault energy does not significantly change with grain size.

The material with higher stacking fault energy has higher fatigue strength whereas the material with lower stacking fault will have a lower fatigue limit.

The higher the width of the stacking fault _________ will be the stacking-fault energy. Higher the stacking fault energy __________ will be the cross slip.

The material with low stacking fault energy is prone to sub-grain formation compared to the metal with high stacking fault energy.

Stainless steel A has a stacking fault energy of 8 mJ.m-2 and stainless steel B has a stacking fault energy of 45 mJ. m-2. The correct statement out of the following are.
P. A will have a wider stacking faults than B
Q. A will strain harden more rapidly than B
R. A and B will develop similar type of substructure
S. A and B will have the same temperature dependence of flow stress.

What is the relationship between the grain size and the fatigue strength for low stacking fault energy material?

The ductile material gives best result in the high strain amplitude or high cycle fatigue, while the strong material gives best result in high-stress low cycle fatigue.

The _______ the stacking-fault energy, the higher the separation between the partial dislocations and the ________ the stacking fault.

With increase in stacking fault energy, fatigue strength of material __________

Compared to mild steel, cast iron has
(i) High compressive strength
(ii) High tensile strength
(iii) Low compressive strength
(iv) Low tensile strength

The largest size of immobilised segment of dislocation in a Frank Read (FR) source contained in a polycrystalline material is of the order of grain size. In a metal of 10 μm grain size, the shear stress required to operate such a FR source is 100 MPa. If the grain size in the same metal is reduced to 10 μm, the shear stress required to operate such FR source would be . . . . . . . . MPa.