1. 30' in total) Answei the following questions. 1.1(6') Briefly describe the advantages of plastic working compared with other methods. 1.2(6') Briefly describe the general classification of metal working processes. 1.3(6) What are the basic mechanisms of the cold plastic deformation of metals? What are the differences between these mechanisms? 1.4(6) What are the influences of cold deformation/working on the microstructure and mechanica properties of metals? 1.5(6) What is recrystallization ? What is the mechanism of softening by recrystallization?

1.1 Plastic working, also known as bulk deformation, involves shaping a metal by applying a force that causes the metal to deform plastically. The advantages of plastic working compared to other methods, such as casting or machining, include the ability to produce complex shapes with high precision and accuracy, the ability to reduce material waste, and the ability to produce parts with improved mechanical properties.<br /><br />1.2 Metal working processes can be classified into several categories, including forming processes, cutting processes, and joining processes. Forming processes involve deforming the metal to shape it, such as forging, rolling, and extrusion. Cutting processes involve removing material from the metal, such as machining and shearing. Joining processes involve combining two or more metal parts, such as welding and brazing.<br /><br />1.3 The basic mechanisms of cold plastic deformation of metals are slip, twinning, and grain boundary sliding. Slip is the movement of dislocations within the crystal structure of the metal, which causes the metal to deform. Twinning is the duplication of a portion of the crystal structure, which also causes deformation. Grain boundary sliding is the movement of grain boundaries within the metal, which can also cause deformation. The differences between these mechanisms are in the way they cause deformation and the resulting microstructure.<br /><br />1.4 Cold deformation/working can have a significant impact on the microstructure and mechanical properties of metals. The deformation can cause changes in the crystal structure, such as the formation of new grains and the growth of existing grains. This can lead to changes in the mechanical properties, such as increased strength and hardness. However, the deformation can also cause defects in the metal, such as dislocations and voids, which can lead to a decrease in ductility.<br /><br />1.5 Recrystallization is the process by which a metal's microstructure is altered by the movement of grain boundaries, resulting in a change in the size and shape of the grains. This process can lead to a softening of the metal, as the new grains are typically larger and have fewer dislocations than the original grains. The mechanism of softening by recrystallization is the reduction in the number of dislocations within the metal, which reduces the resistance to plastic deformation.