As the temperature increases , the inter atomic distance also increases. So it result in a increase in area ( stress = force /area ) As the area increases stress decreases this result in a decrease in Young's modulus.

Modulus of elasticity, also known as Young's modulus, is a material property that describes its stiffness or ability to withstand deformation when subjected to an applied force. It is defined as the ratio of stress to strain within the elastic limit of the material. The modulus of elasticity is an important parameter in engineering applications as it helps determine the behavior of materials under different loading conditions.

The modulus of elasticity is influenced by various factors, including temperature. Let's explore how the modulus of elasticity changes with temperature:

1. Atomic Vibrations:
At higher temperatures, the atoms within a material vibrate with greater energy due to increased thermal energy. These atomic vibrations cause the material to expand, leading to an increase in strain. As a result, the modulus of elasticity decreases with an increase in temperature.

2. Dislocation Movement:
At lower temperatures, the movement of dislocations in the crystal lattice is limited, leading to higher stiffness and a higher modulus of elasticity. However, as the temperature increases, the thermal energy allows for more dislocation movement, which reduces the stiffness and decreases the modulus of elasticity.

3. Bond Energy:
The strength of the atomic bonds within a material can be affected by temperature. At higher temperatures, the bond energy decreases, making the material more susceptible to deformation. This decrease in bond energy leads to a decrease in the modulus of elasticity.

4. Phase Transformations:
Some materials undergo phase transformations at specific temperatures. For example, metals may undergo phase changes from a crystalline to an amorphous structure. These phase transformations can significantly affect the modulus of elasticity, leading to changes in stiffness.

5. Composite Materials:
Composite materials consist of different phases or constituents with varying properties. The modulus of elasticity of composite materials can be influenced by the thermal expansion coefficients of the individual constituents. As the temperature changes, the different constituents may expand or contract at different rates, affecting the overall stiffness and modulus of elasticity of the composite material.

In conclusion, the modulus of elasticity generally decreases with an increase in temperature. This is due to factors such as atomic vibrations, dislocation movement, changes in bond energy, phase transformations, and the behavior of composite materials. It is important to consider the temperature dependence of the modulus of elasticity when designing and analyzing materials for various applications.