Q1: Fine grain size in metallic material will

ANS:C - increase the fatigue strength.

Fine grain size in metallic materials generally leads to:

1. Increase in Yield Strength: Fine grain size typically increases the yield strength of the material. This is because smaller grains create more grain boundaries, which act as barriers to dislocation movement, making it more difficult for the material to deform plastically.
2. Increase in Creep Strength: Fine grain size can also increase the creep strength of the material. Creep is the gradual deformation of a material under constant stress at high temperatures. Smaller grains inhibit the movement of dislocations and reduce the rate of creep deformation.
3. Increase in Fatigue Strength: Fine grain size tends to increase the fatigue strength of the material. Fatigue strength is the ability of a material to withstand cyclic loading without failure. Smaller grains distribute stress more evenly, reducing the likelihood of crack initiation and propagation, thus improving fatigue resistance.
4. Decrease in Impact Strength: Fine grain size may decrease the impact strength of the material. Impact strength is the ability of a material to withstand sudden loads or shocks without fracturing. Smaller grains provide fewer obstacles to crack propagation, making the material more susceptible to brittle fracture under impact loading.

In summary, while fine grain size generally improves yield strength, creep strength, and fatigue strength, it may decrease impact strength due to increased susceptibility to brittle fracture. However, the specific effects of grain size on material properties can vary depending on factors such as alloy composition, processing methods, and testing conditions.