Primary objective of full annealing is to increase ductility and machinability

Introduction:
Full annealing is a heat treatment process that involves heating a material to a specific temperature, holding it at that temperature for a period of time, and then slowly cooling it down. This process is commonly used to improve the mechanical properties and machinability of metals.

Explanation:
The primary objective of full annealing is to increase the ductility and machinability of a material. Here's how it achieves these objectives:

1. Increase in Ductility:
- Ductility refers to the ability of a material to undergo plastic deformation without fracturing.
- Full annealing involves heating the material to a temperature above its upper critical temperature, which allows the atoms to rearrange themselves and reduce any internal stresses or dislocations.
- As a result, the material becomes more homogeneous and its grain structure is refined.
- The refined grain structure leads to improved ductility because the finer grains are able to deform more easily without causing fractures.
- This increased ductility is desirable in many applications, such as forming and shaping processes, where the material needs to be bent or stretched without breaking.

2. Increase in Machinability:
- Machinability refers to the ease with which a material can be machined or shaped using cutting tools.
- Full annealing can improve machinability by reducing the hardness of the material.
- When a material is too hard, it can cause excessive tool wear and poor surface finish during machining operations.
- By annealing the material, its hardness is reduced, making it easier to machine and resulting in better surface finish.
- Additionally, the refined grain structure obtained through annealing can also contribute to improved machinability as it reduces the occurrence of built-up edge and chip formation problems.

Conclusion:
In summary, the primary objective of full annealing is to increase the ductility and machinability of a material. By refining the grain structure and reducing internal stresses, full annealing improves the material's ability to deform without fracturing and makes it easier to machine. This makes the material more suitable for various applications where ductility and machinability are important factors.