Basic Engineering Materials Quiz!

The study of metallographic includes failure analysis, metal structure, and alloy constituents. Metallography is a branch of material science that focuses on the microscopic examination of metals and alloys. It involves analyzing the structure, composition, and properties of metals to understand their behavior, performance, and potential failure mechanisms. By studying metallography, one can gain insights into the causes of failures, the effects of different alloy constituents on the material's properties, and the relationship between the metal's structure and its performance.

Plasticity refers to the ability of a material, in this case metal, to permanently deform and not regain its original shape after the deforming force is removed. This means that the metal will retain its new shape even if the force is no longer applied. Ductility, on the other hand, refers to the ability of a material to be stretched or drawn into a wire without breaking, while elasticity refers to the ability of a material to regain its original shape after being deformed. Stiffness refers to the resistance of a material to deformation.

The machinability of a metal refers to how easily it can be cut, shaped, or formed using machining processes. Hardness and tensile strength are two important factors that influence the machinability of a metal. A metal with high hardness and tensile strength may be more difficult to machine compared to a metal with lower hardness and tensile strength. This is because harder and stronger metals are more resistant to cutting and require more force to be applied during machining. Therefore, hardness and tensile strength are key considerations when determining the machinability of a metal.

Ductility is the property of a material that allows it to be drawn into thin wires without breaking. This property is essential for many applications, such as electrical wiring and jewelry making. Metals are known for their high ductility, as they have metallic bonds that allow the atoms to easily slide past each other when a force is applied. This enables the metal to be stretched and formed into a wire shape without losing its integrity. Malleability, on the other hand, refers to the ability of a material to be hammered or rolled into thin sheets. Plastic deformation and elastic deformation are not specifically related to the ability to be drawn into wire.

Toughness is the desirable property in parts subjected to shock and impact loads because it measures a material's ability to absorb energy and deform plastically before fracturing. This means that a tough material can withstand sudden and intense forces without breaking or shattering, making it ideal for applications where impact resistance is crucial. Brittleness, on the other hand, refers to a material's tendency to fracture without significant deformation, making it unsuitable for shock and impact loads. Strength and stiffness are important properties as well, but they do not specifically address the ability to withstand shock and impact loads.

The atomic packing efficiency of a face-centered cubic (FCC) lattice is 74%. This means that 74% of the total volume in the lattice is occupied by atoms, while the remaining 26% is empty space. In an FCC lattice, atoms are arranged in a close-packed structure, with each atom surrounded by 12 nearest neighbors. This arrangement allows for efficient packing of atoms, resulting in a high packing efficiency of 74%.

Magnesium has a hexagonal close-packed (HCP) crystal structure. In this structure, the metal atoms are arranged in a close-packed pattern with each atom surrounded by six nearest neighbors forming a hexagonal shape. This arrangement allows for efficient packing of atoms, resulting in a dense and stable structure. Silver, Iron, and Aluminium do not have a hexagonal close-packed structure.

The given elements, zinc, magnesium, cobalt, cadmium, antimony, and bismuth, have a closed packed hexagonal space lattice. This means that their atoms are arranged in a hexagonal pattern with the maximum number of atoms packed together in a given space. The other options, gamma-iron, aluminium, copper, lead, silver, nickel, alpha-iron, tungsten, chromium, and molybdenum, do not have a closed packed hexagonal space lattice.

In a body-centered cubic (BCC) structure, there are 2 atoms per unit cell. This can be understood by visualizing the arrangement of atoms in a BCC lattice, where one atom is located at the center of the cube and another atom is at each of the eight corners. The atom at the center is shared by eight adjacent unit cells, while the atoms at the corners are only present in one unit cell each. Therefore, the total number of atoms per unit cell in BCC is 2.

The correct answer is FCC (Face-centered cubic). Brass is an alloy made primarily of copper and zinc, and it has a FCC crystal structure. In a FCC structure, the lattice points are located at the corners and centers of all the faces of the unit cell. This arrangement allows for close packing of atoms and results in a highly symmetric structure. The FCC structure is commonly found in many metallic elements and alloys, including copper, aluminum, and gold.

An optical microscope is used to determine magnification in the range of 60x to 2000x linear magnification. This type of microscope uses visible light and lenses to magnify the sample being observed. It is commonly used in biology and other scientific fields to study small organisms, cells, and tissues. An electron microscope, on the other hand, uses a beam of electrons to magnify the sample and is capable of much higher magnification, but it is not relevant to the given range. Unaided eyes cannot achieve such high levels of magnification. Therefore, the correct answer is an optical microscope.

Nital and Picral are both etching reagents used for carbon steels. Nital is a mixture of nitric acid and ethanol, while Picral is a mixture of picric acid and ethanol. These reagents are used to reveal the microstructure of carbon steels by selectively attacking the grain boundaries and phases present in the material. Both a and b are correct options as they represent the two commonly used etching reagents for carbon steels.

The correct answer is "Creep". Creep refers to the gradual deformation of a material under constant stress at high temperatures. It occurs over an extended period of time and is a result of the material's internal structure rearranging itself. This phenomenon is commonly observed in materials such as metals and polymers, and it can lead to permanent deformation or failure of the component if not properly accounted for in design and engineering processes.

Gold has a face-centered cubic structure. In this type of structure, the atoms are arranged in a cubic lattice with an atom at each corner and an additional atom at the center of each face of the cube. This arrangement provides a close packing of atoms and is commonly found in metals, including gold.

The rollers of a cycle chain are subjected to fatigue stress. Fatigue stress is the stress that occurs when a material is subjected to repeated loading and unloading, leading to the weakening and eventual failure of the material. In the case of a cycle chain, the rollers experience repeated stress as they rotate and engage with the teeth of the gears, causing fatigue stress to build up over time. This can eventually lead to the failure of the rollers, resulting in the chain breaking or becoming ineffective.

The body-centered cubic (BCC) space lattice is found in alpha-iron, tungsten, chromium, and molybdenum. This lattice structure consists of atoms arranged in a cubic lattice with an atom at the center of the cube and one at each of the eight corners. This arrangement provides stability and strength to these materials, making them suitable for various applications. The other options mentioned in the question, such as gamma-iron, aluminium, copper, lead, silver, nickel, zinc, magnesium, cobalt, cadmium, antimony, and bismuth, do not have a body-centered cubic structure.

Mild steel has maximum ductility compared to copper, nickel, and aluminum. Ductility refers to the ability of a material to deform under tensile stress without breaking. Mild steel is known for its high ductility, which allows it to be easily shaped and formed into various structures. Copper, nickel, and aluminum also possess ductility, but mild steel surpasses them in terms of maximum ductility.

Creep is an important consideration in the case of gas turbine blades. Creep refers to the gradual deformation of a material under constant stress over time. Gas turbine blades are subjected to high temperatures and mechanical stresses, which can cause them to deform over time if creep is not taken into account. Therefore, understanding and accounting for creep is crucial in the design and operation of gas turbine blades to ensure their structural integrity and performance.

Zirconium does not have a body centred cubic (BCC) structure. It has a hexagonal close-packed (HCP) structure instead. Body centred cubic structure is characterized by a lattice with atoms located at the corners and one atom at the centre of the cube. Chromium, potassium, and lithium all have a BCC structure.

Zinc has the lowest melting point among the given options. Zinc has a melting point of 419.53°C (787.15°F), which is relatively low compared to the other metals listed. Antimony has a melting point of 630.63°C (1167.13°F), silver has a melting point of 961.78°C (1763.2°F), and tin has a melting point of 231.93°C (449.47°F). Therefore, tin has the lowest melting point among these metals.