Engineering Materials MCQ Questions & Answers | Mechanical Engineering

Recrystallization temperature can be lowered by Purification of metal and Grain refinement and Working at lower temperature

Ductility of a material has been defined as a ability of a material to undergo permanent deformation through elongation and reduction in cross-sectional area or bending at room temperature without fracturing.

Malleability is a physical property of metals that defines the ability to be hammered, pressed or rolled into thin sheets without breaking.

Resilience: The ability of a material to absorb energy under elastic deformation and to recover this energy upon removal of load is termed as resilience. Resilience is indicated by the area under the stress strain curve till the point of elastic limit.

Creep: It is a deformation of a material due to the constant load for a long period of time. It is time and temperature dependent property of material.

Fatigue: When a body is subjected to repeated and fluctuating load it tends to develop a characteristic behavior under which failure occurs which is referred to as fatigue.

Toughness: The ability of a material to absorb energy in plastic deformation till the point of fracture is known as toughness. Toughness is indicated by the total area under the stress strain curve up to the fracture point. Eg. Copper has higher toughness than Cast iron.

Muntz metal is about 60% copper, 40% zinc

Bronze is an alloy consisting primarily of copper, commonly with about 12 - 12.5% tin and often with the addition of other metals (such as aluminium, manganese, nickel or zinc) and sometimes non-metals or metalloids such as arsenic, phosphorus or silicon.

Brittle Fracture is the sudden, very rapid cracking of equipment under stress where the material exhibited little or no evidence of ductility or plastic degradation before the fracture occurs.
metals with hexagonal close packed (H.C.P) crystal structure commonly show brittle fracture

Brass contains 70% copper and 30% zinc

Option A: Correct. Wrought iron contains very low carbon, generally less than 0.08%, but often described as being in the order of 0 to 0.25%.

Option B: Incorrect. The melting point of pure iron is about 1535°C. Wrought iron, due to impurities such as slag, has a slightly lower melting point, usually around 1500°C or even lower. Hence, this statement is wrong.

Option C: Correct. Wrought iron is very soft, malleable, and ductile because of its low carbon content.

Option D: Partially misleading but acceptable in context. Wrought iron is produced by removing carbon and impurities from pig iron, and the hammering/rolling process helps eliminate slag inclusions and improves its structure. It is not made by adding carbon, but the focus is on refining.

Therefore, the wrong statement about wrought iron is: Option B: It melts at 1535°C.

Below 912°C (1,674°F) iron again adopts the BCC structure characteristic of α-iron, also called ferrite.
The substance assumes a paramagnetic property. Carbon dissolves poorly in α-iron: no more than 0.021% by mass at 723°C