Engineering Materials - Study Mode

[#71] Bronze is an alloy of
Correct Answer

(B) Copper and tin

Explanation

Solution: 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.

[#72] Manganese is added in low carbon steel to
Correct Answer

(C) Make the steel ductile and of good bending qualities

Explanation

Solution: The effect of manganese in improving the mechanical properties of steel depends on its carbon content. Manganese also reduces the critical cooling rate during hardening, meaning it increases the hardenability of steel. Its effect on hardenability is higher than other alloying elements. Hadfield steel is recognized for its ability to be work-hardened due to the addition of 10% to 14% of manganese.

[#73] The elastic stress strain behavior of rubber is
Correct Answer

(B) Nonlinear

Explanation

Solution: The most common example of this kind of material is rubber, whose stress-strain relationship can be defined as non-linearly elastic, isotropic, in compressible and generally independent of strain rate. Hyper elasticity provides a means of modeling the stress–strain behavior of such materials

[#74] The following element can't impart high strength at elevated temperature
Correct Answer

(B) Magnesium

Explanation

Solution: The strength, hardness, and modulus of elasticity of magnesium-base materials decrease with increasing temperature. Also, the elongation increases with rising temperature up to just below the melting point where it drops to nearly zero

[#75] In process annealing, the hypo eutectoid steel is
Correct Answer

(D) Heated below or closes to the lower critical temperature and then cooled slowly

Explanation

Solution: The correct answer is D: Heated below or close to the lower critical temperature and then cooled slowly . Let's break down why: Process Annealing is a heat treatment used to relieve internal stresses in a cold-worked metal without significantly altering its microstructure. Think of it like giving the steel a gentle "relaxing massage". Hypo-eutectoid steel means the steel has less than 0.8% carbon. Critical Temperatures are important points where the steel's crystal structure changes. We have an Upper Critical Temperature (A3) and Lower Critical Temperature (A1). Now, let's look at the options: Options A, B, and C involve heating *above* the upper critical temperature. Heating above A3 causes the steel to transform into austenite, then cooling in different ways controls the formation of new microstructures. This is used for other heat treatments like normalizing or quenching, not process annealing . Option D is different. Heating "below or close to the lower critical temperature" means we're only heating it enough to reduce stress, *without* changing its fundamental structure. Then, cooling slowly helps to further relax the steel. Therefore, the key to process annealing of hypo-eutectoid steel is heating *below* the lower critical temperature, making Option D the correct choice.