Can you describe the meaning of the following terms in English? 2. What does crystalline structure mean? 4

2. "Crystalline structure" refers to the arrangement of atoms or molecules in a solid material. In a crystalline structure, the atoms are organized in a repeating pattern, forming a three-dimensional lattice. This arrangement leads to the formation of well-defined crystal faces and characteristic geometric shapes. Crystals can have various shapes, such as cubes, pyramids, or hexagons, depending on the type of crystal structure. The regular arrangement of atoms in a crystalline structure gives the material its unique properties, such as hardness, transparency, and ability to reflect light in specific directions.

4. "Heat treatment" is a process used to alter the properties of a material through the controlled application of heat. It involves heating a material to a specific temperature and then cooling it down in a controlled manner. Heat treatment can be used to modify various characteristics of a material, such as its hardness, strength, ductility, toughness, and even its microstructure.

The main purposes of heat treatment are to improve the mechanical properties of a material, enhance its machinability, relieve internal stresses, and increase its resistance to wear, corrosion, or other forms of degradation. The specific heat treatment method employed depends on the type of material and the desired outcome. Common heat treatment processes include annealing, quenching, tempering, and case hardening.

6. "Creep" refers to the gradual deformation that occurs in a material subjected to a constant load or stress over a prolonged period of time at high temperatures. It is a time-dependent phenomenon and typically happens in materials such as metals, plastics, and geological formations.

Creep occurs due to the movement of atoms or molecules within the material, which leads to a permanent change in shape or dimensions. It can be visually observed as a progressive elongation or deformation of the material over time. The extent of creep depends on factors such as temperature, stress level, and the nature of the material.

Creep has significant implications in engineering and material science, as it can cause structural instability, fatigue, and failure over extended periods. It needs to be considered and accounted for in the design and manufacturing processes of high-temperature applications, such as in gas turbines, boilers, and structural components used in aerospace or power generation industries.