Engineering Materials MCQ Questions & Answers | Mechanical Engineering

Nickel (Ni): Nickel is added in large amounts, over about 8%, to high Chromium stainless steels to form the most important class of corrosion and heat resisting steels.

Depth of hardness refers to how deeply into the steel hardness can extend after a hardening process such as quenching. This property is linked to the hardenability of the steel.

Chromium is the most effective alloying element for increasing the depth of hardness. It improves the steel’s hardenability by slowing down the transformation of austenite to softer phases, allowing martensite to form deeper within the material. This ensures that not just the surface but also the interior can achieve significant hardness.

Nickel improves toughness and corrosion resistance but has little effect on depth of hardness.

Tungsten increases wear resistance and hot hardness (retention of hardness at high temperatures), but it is less effective for depth of hardness compared to chromium.

Vanadium refines grain size and enhances wear resistance, but its influence on hardenability depth is secondary.

Therefore, Chromium is the alloying element most responsible for increasing the depth of hardness of steel.

Anisotropy, is the property of being directionally dependent, which implies different properties in different directions, as opposed to isotropy.

Iron-carbon alloys containing carbon more than 4.3% are known as hyper-eutectic cast irons.
hypereutectic cast iron (>4.3 % C).

Annealing of steels Increased cold shaping possibilities because intermediate annealing can be utilized to improve the forming properties after the material is compressed during other operations such as cold heading.
Annealing of steels Reduced chance of distortion during secondary operations such as machining.
Annealing of steels Controlled atmosphere annealing decreases the chance of oxidation to annealed parts.
Annealing of steels Improved reaction time and greater control of emergency product need fulfillment.

Annealing of steels increased cold shaping possibilities because intermediate annealing can be utilized to improve the forming properties after the material is compressed during other operations such as cold heading.
Annealing of steels reduced chance of distortion during secondary operations such as machining.
Annealing of steels controlled atmosphere annealing decreases the chance of oxidation to annealed parts.
Annealing of steels improved reaction time and greater control of emergency product need fulfillment.

In eutectoid reaction, the austenite transforms into a phase mixture of ferrite (containing 0.76% C) and cementite.
This phase mixture is known as pearlite.
The eutectoid reaction occurs at a constant temperature.
This is known as eutectoid temperature and is 727°C.

When steel containing less than 0.8% carbon is cooled slowly from temperatures above or within the critical range, it consists of Ferrite and pearlite

Aluminum metal is used to make many parts produced by precision machining, and is finding increasing application in automotive because of its light weight and high strength to weight ratio.

Admiralty metal is an alloy of not less than 70 percent copper, about 1 percent tin, small amounts of other elements, and the balance zinc; tin brass.
Admiralty metal shrinks most from molten state to solid state