FERROUS & NON - FERROUS ALLOYS SET 05

FERROUS & NON - FERROUS ALLOYS SET 05

1. Which of the following parts are mostly manufactured by using copper alloys?
a) Pistons
b) Engine blocks
c) Journal bearings
d) Aircrafts
 

Answer: c
 

Explanation: In the manufacturing of journal and other types of solid bearings, copper alloys are mostly preferred. Many other components like worm wheels, gear selector forks and electricity wires are also made by using copper alloys; it is mostly preferred where low friction and high wear resistance is required.
 

2. Copper alloys generally have sparking nature due to its high ductility.
a) True
b) False
 

Answer: b
 

Explanation: Copper alloys components are generally of non-sparking nature, that’s why they are preferred in manufacturing of electrical equipment and components where there is a chance of fire hazard. And the ductile nature of copper alloys is totally independent to its non-sparking nature.
 

3. Copper alloys have low thermal conductivity but high electrical conductivity.
a) True
b) False
 

Answer: b
 

Explanation: Copper alloys have high thermal conductivity as well as high electrical conductivity. Due to high electrical conductivity, they are used in making of electric wires, in motor winding etc. And high thermal conductivity of copper alloys useful in making of heat exchangers, in piping of power-plants, air conditioning, refrigerators etc.
 

4. Copper alloys possess good mechanical properties even at high temperatures.
a) True
b) False
 

Answer: a
 

Explanation: Copper and its alloys have an optimized combination of tensile and compressive strength, hardness, ductility and resistance to shock load to use for various applications. And the mechanical properties of copper alloys at high temperatures are even better than the other non-ferrous materials.
 

5. At zero level temperature of copper alloys, they become very hard and brittle in nature.
a) True
b) False
 

Answer: b
 

Explanation: At zero level temperature of copper alloy castings, no any kind of embrittlement occurs; in fact, the tensile strength of copper castings enhances at low temperature. Therefore, the copper castings can be used at very low temperatures without any significant changes to the properties of the castings.
 

6. Castings or components of copper alloys have high machinability and recyclability.
a) True
b) False
 

Answer: a
 

Explanation: Many alloys consist of lead to increase machinability with easy chip formation. But, copper components itself have excellent machinability. And copper alloy castings are recyclable too, the scrapes of copper alloys castings can be melted and can be used again in the manufacturing of other copper parts.
 

7. In general, copper is highly reactive with sulphur and its chemical compounds.
a) True
b) False
 

Answer: a
 

Explanation: Copper may resists the oxidation, but it is highly reactive with sulphur and its chemical compounds, it produces copper sulphide during the reaction which can be unpleasant for the casting components. The main copper contaminants significantly are phosphorous and iron besides oxygen.
 

8. Copper is generally a polymorphous material with body centered cubic (BCC) lattice structure.
a) True
b) False
 

Answer: b
 

Explanation:Copper is a non-polymorphous material with face centered cubic (FCC) structure. The FCC structure is the only reason for ductility in the copper material. Pure copper is generally reddish in color, and addition of zinc produces the yellow color of the copper and nickel produces the silver color of the same.
 

9. It is very difficult to cast pure copper metal in mould cavity because of shrinkage problems.
a) True
b) False
 

Answer: a
 

Explanation: It is very difficult to cast pure copper in mould cavity because very large shrinkages occur during the solidification of castings, and a large amount of gasses are trapped in the casting at high temperatures which results in the melted material gassing and the porosity in casting components.
 

10. Pure magnesium melts at what temperature?
a) 600°C
b) 650°C
c) 700°C
d) 750°C
 

Answer: b
 

Explanation: The temperature at which the pure form of magnesium gets ignited by itself is 473°C, and the temperature at which magnesium in its purest form is found to melt is 650°C.