Engineering Materials MCQ Questions & Answers | Mechanical Engineering

Phosphorous, lead and sulphur improves machinability and resistance to corrosion and it intensifies the effects of other alloying elements

Hardness is a measure of the resistance to localized plastic deformation induced by either mechanical indentation or abrasion.

The correct answer is D: All of these
Let's break down why:

Option A: Carbon in the form of carbide - This is true. White cast iron gets its hardness and brittleness because the carbon is chemically bonded with iron to form iron carbide (Fe3C), also known as cementite.

Option B: Low tensile strength - This is also true. Tensile strength refers to how well a material resists being pulled apart. Because of the hard, brittle iron carbide structure, white cast iron is very poor at resisting tensile forces; it breaks easily when pulled or stretched.

Option C: High compressive strength - This is also true. Compressive strength refers to how well a material resists being crushed. The hard carbide structure in white cast iron *does* make it quite good at resisting compressive forces.

Since all three options (A, B, and C) are correct statements about white cast iron, the best answer is D: All of these.

When a steel containing less than 0.8% carbon is cooled slowly below the lower critical point, it consists of ferrite and pearlite.

The ratio of the volume occupied by the atoms to the total volume of the unit cell is called Atomic packing factor

Smelting is a process of applying heat to ore in order to extract out a base metal.
It is a form of extractive metallurgy.
It is used to extract many metals from their ores, including silver, iron, copper, and other base metals

Induction hardening is a process used for the surface hardening of steel and other alloy components.
The parts to be heat treated are placed inside a water cooled copper coil and then heated above their transformation temperature by applying an alternating current to the coil.

A process in which an iron-base alloy is heated in contact with a cyanide salt so that the surface absorbs carbon and nitrogen.
Cyaniding is followed by quenching and tempering to produce a case with a desired combination of hardness and toughness.

Stress relaxation is a gradual reduction in stress with time at constant strain.
Stress relaxation occurs in polymers when they are held in a strained state for long periods of time.
These alloys have very good resistance to stress relaxation and are therefore used as spring materials.

spheroidal graphite iron, in which graphite appears as spherical nodules and ductility is greatly increased.