What is meant by 'work hardening' in metal processing?

'Work hardening,' also known as strain hardening, refers specifically to the technique of strengthening a metal through deformation. This phenomenon occurs when a metal is subjected to mechanical stress, causing dislocations in the crystalline structure of the material. As the metal is deformed, these dislocations interact and multiply, which makes it increasingly difficult for further deformation to take place. This results in an increase in the strength and hardness of the material.

This process is particularly significant in metalworking because it allows fabricators to enhance the mechanical properties of metals such as steel or aluminum without the need for heat treatment techniques. With the right application of stress—such as bending, rolling, or drawing—metals can be tailored for specific applications and improved performance under load.

The other choices do not accurately capture the concept of work hardening. Cleaning metals before machining is a preparatory process unrelated to the strength of the material itself. Reducing the weight of metals does not align with the notion of work hardening, as hardening typically increases density and strength rather than decreases weight. Lastly, alloying different metals together is a separate metallurgical process involving mixing metals to create new materials with distinct properties, not directly tied to deformation and strengthening of a single metal.