Modulus of elasticity and Micro structure

Modulus of Elasticity

This property reflects the ability of a material to resist deflection when subjected to external loads. Greater the value of modulus of elasticity lesser is the deflection under load.

Materials with moderate or low modulus of elasticity tend to deflect more under cutting force and hence must be machined with a sharp cutting edge, i.e. with positive rake tool. Material with larger modulus of elasticity is more rigid and hence requires a tool with high strength cutting edge (negative rake).

Microstructure

Microstructure has considerable influence on the machinability of a material. For example the microstructure of steel consists of basic constituents of ferrite, pearlite and cementite. Cementite is the hardest, ferrite the softest and pearlite in between. The proportion of cementite, pearlite and ferrite in the mcirostructure will determine the hardness of the material. Similarly the amount of carbides in the microstructure would also influence the hardness of the material. Thus the microstructure of a material affects the cutting force and power to the extent it affects the hardness and tensile strength of the material.