A measure of the rigidity of a material is called the modulus of elasticity. Specifically, the slope of the initial linear portion of the stress-strain curve is the modulus of elasticity; when obtained in compression or tension it is Young’s modulus. Since the modulus of elasticity is needed for computing deflection of beams and other members in a structure, it is an important design value.
The modulus of elasticity is determined by the binding forces between the atoms in the material. These forces cannot be changed without changing the basic nature of the material, and it follows that modulus of elasticity is one of the most structure-insensitive of all the mechanical properties. The modulus of elasticity is only slightly affected by alloying additions, heat treatment or cold work. However, only increasing the temperature
results in a decrease in the modulus of elasticity.