请回答上述六个问题用英文回答

Sure, here are the answers to the questions in English: 1. With reference to slip planes and crystal dislocations, describe how deformations move through crystalline material and how this affects the mechanical behaviour of the material. - Slip planes and crystal dislocations play a crucial role in the deformation of crystalline materials. When a stress is applied to a crystal, it causes the atoms to shift along specific planes called slip planes. These shifts occur due to the presence of dislocations, which are line defects in the crystal lattice. Dislocations act as sources for plastic deformation, allowing the crystal to slide past itself without breaking. This process affects the mechanical behavior of the material by determining its strength, ductility, and hardness. 2. How can impurities or ‘defects’ in a crystal structure help to prevent the deformation of a material and therefore increase its hardness? Give several examples of these ‘defects’. - Impurities and defects in a crystal structure can hinder the movement of dislocations, making it more difficult for the material to deform plastically. This results in increased hardness. Examples of such defects include: - Point defects: Vacancies, interstitial atoms, and substitutional atoms. - Line defects: Edge dislocations and screw dislocations. - Planar defects: Grain boundaries and twin boundaries. - Volume defects: Porosity and inclusions. 3. With reference to metals’ crystal structure, explain how work hardening occurs. Give one real life example of a material that work hardens. - Work hardening, also known as strain hardening, occurs when a metal is deformed plastically, causing an increase in its strength and hardness. This happens because the deformation introduces dislocations into the crystal lattice, which interact with each other and with other defects, making further deformation more difficult. A real-life example of a material that work hardens is cold-rolled steel, which becomes stronger and harder after being rolled at room temperature. 4. With reference to the idea of crystal grain size, explain the function of quenching metal in terms of the mechanical properties which are produced. - Quenching is a heat treatment process that involves rapidly cooling a metal from a high temperature to produce a fine-grained microstructure. The rapid cooling prevents the formation of large grains and promotes the formation of small, uniform grains. This fine-grained structure enhances the mechanical properties of the metal, such as increasing its strength, hardness, and toughness. 5. Describe three different processes that are used in shaping a metal product. Compare and contrast them in terms of precision, ease of processing, cost and other relevant characteristics. Give a real life example of how one of the processes is carried out. - Three common processes for shaping metal products are casting, forging, and machining. - Casting: Involves pouring molten metal into a mold and allowing it to solidify. It is relatively inexpensive but may have lower precision compared to other methods. - Forging: Involves applying pressure to shape the metal while it is hot. It offers good control over the final shape and can improve the mechanical properties of the metal. - Machining: Uses cutting tools to remove material from a workpiece to achieve the desired shape. It provides high precision but can be more expensive and time-consuming. - Real-life example: Forging is often used to manufacture automotive parts, where precise control over the shape and improved mechanical properties are essential. 6. Describe key processes occurring in annealing of a metal or metal alloy. Explain clearly how residual stresses and grain size changes with the duration and temperature used for the annealing. Describe using a real life example how this may affect the mechanical properties of the resulting product. - Annealing is a heat treatment process that involves heating a metal or alloy to a specific temperature and then slowly cooling it. The key processes during annealing include recovery, recrystallization, and grain growth. Recovery reduces internal stresses and dislocation density, while recrystallization forms new, defect-free grains. Grain growth occurs as the new grains grow larger. The duration and temperature of annealing determine the extent of these processes, affecting the residual stresses and grain size. Longer annealing times and higher temperatures generally result in larger grains and reduced residual stresses. - Real-life example: Annealing is commonly used to soften and improve the formability of aluminum sheets before they are stamped into automobile body panels. The annealing process helps to reduce residual stresses and refine the grain structure, leading to better mechanical properties and easier processing.