Question

The strength of grain boundary and grains are equal:

• A. At equi cohesive temperature
• B. Above equi cohesive temperature
• C. Below equi cohesive temperature
• D. At recrystallisation temperature

Hint:

Remember: At equi cohesive temperature, grain boundaries and grain interiors possess equal strength — crucial for uniform deformation and resistance to intergranular failure.

Answer 1

The Correct Option is A

The equi cohesive temperature is defined as the temperature at which the cohesive strength (or bonding strength) of the grain boundaries becomes equal to that of the grains themselves.
At temperatures below the equi cohesive point, grain boundaries are generally weaker and more prone to fracture or failure, especially under stress or thermal cycling. Above this temperature, grain boundaries may exhibit stronger behavior, but often at the expense of other mechanical properties.
Therefore, the strength of the grains and their boundaries is equal only at the equi cohesive temperature, marking a critical point in the thermal-mechanical behavior of polycrystalline materials.
This concept is important in high-temperature applications where uniform mechanical behavior across grains and boundaries is desired.