Unit 05 METALS AND THEIR ALLOYS, Materials Engineering Important Questions with answer

Let’s Explore the Unit 05 METALS AND THEIR ALLOYS, Materials Engineering Important Questions with answer. Hope this important questions will help you in your Exams.

Q1. Discuss about the microstructure of ferrous, non-ferrous metals and alloys. 

Ans.
A. Microstructure of Ferrous Metals: 

• 1. In ferrous metals iron is the chief constituent. 
• 2. In addition to iron, the ferrous metals contain carbon, nickel, phosphors and manganese. 
• 3. Following are the some common ferrous metals used in engineering are as follows :  

a. Microstructure of Mild Steel: 

• 1. In mild steel, carbon presents up to 0.2 % in ferrite form (Fe₃ C). 
• 2. Ferrite has a flaked type structure and grain sizes are different and irregular in shape. 
• 3. The percentage of iron upto 98 % is present in the mild steel. 

b. Microstructure of Cast Iron: 

• 1. The carbon percentage varies from 2 to 4.3 o in cast iron. 
• 2. The structure of cast iron contains graphite flakes in ferrite/pearlite matrix. 
• 3. The graphite flakes are about 0.05 to 0.1 mm length. These flakes occupy 10 % of the metal volume. 

B. Microstructure of Non-Ferrous Metals and Alloys:

• 1. Non-ferrous metals are those which do not contain iron. 
• 2. Most of the non-ferrous metals have high electrical conductivity, low density and high strength to weight ratio. 
• 3. Some important non-ferrous and alloys are as follows :  

a. Microstructure of Copper : 

• 1. It is a reddish brown metal. 
• 2. It has crystalline (FCC) structure. 
• 3. It is soft, malleable and good conductor of electricity. 

b. Microstructure of Aluminium: 

• 1. It is a white lustrous metal. 
• 2 It is highly malleable and ductile. 
• 3. It is a good conductor of heat and electricity. 
• 4. Pure aluminum is highly resistant to corrosion and is easily cast to the required shape. 
• 5. It has good machinability and cold and hot working. 

Q2. Discuss effects of alloying elements on the properties of steel.

Ans. 1. Steel is the most commonly used alloy of iron. Alloying elements are added to effect changes in the properties of steel.

2. The effects of various alloying elements on steel are given below:

Q3. Explain the properties and use of types of stainless steels commonly used in industries.  

Ans. Types of stainless steels used in industries are as follows: 

a. Martensitic Stainless Steel: 

i Properties: 

• 1. . Martensitic stainless steel contains 12 to 17 % Crwith sufficient carbon. 
• 2. It is capable of being heat treated in such a way that the martensite is the prime micro-constituent. 
• 3. It is hardenable and magnetic. 

ii. Applications: Valves, pumps, surgical instruments, razors, blades, turbine blades, etc.

b. Ferritic Stainless Steel: 

i. Properties:

• 1. Ferritic stainless steel contains 12 to 30 % Cr with low carbon. 
• 2. It is mostly composition of a ferrite (BCC) phase. 
• 3. It is soft, ductile, corrosion resistant and magnetic.   

ii. Applications: Combustion chamber, lining for petroleum industry, furnace parts, nozzles, gas burners, vessels in chemical industry, etc.

c. Austenitic Stainless Steel:

i. Properties:

• 1. Austenitic stainless steel contains 16 to 25 % Cr and 7 to 20% Ni. 
• 2. Its crystal structure contains FCC structure. Due to FCC structure it is highly formable. 
• 3. It is non-magnetic.

ii. Applications : Household utensils, steam pipes, boiler tubes, radiant superheater tubes, etc.

Q4. Discuss about cast iron, its properties and uses.  

Ans. A. Cast Iron: 

• 1. Cast iron is very useful engineering material. It contains more carbon percentage (approximately 2 % < C< 4.5 %). 
• 2. When pig iron is melted with coke and limestone in cupola furnace, it produces cast iron.  
• 3. Coke acts as a fuel and limestone acts as flux.  
• 4. Fluxes are used to separate the impurities from the pig iron (like oxides and fuel ash etc.). 

B. Properties of Cast Iron:

• 1. It has good hardness due to presence of high carbon percentage. 
• 2. Its compressive strength is very good. 
• 3. It has good machinability. 
• 4. It has very good rigidity. 

C. Uses of Cast Iron: 

• 1. The most important use is to make the bed of lathe machines. 
• 2. It is used for making the body structures of tools. 
• 3. To reduce the cost of an IC engine, cylinder head and blocks are made of cast iron. 
• 4. Leaf springs or laminated springs are made of cast iron. 
• 5. Underground pipelines to supply oils and natural gases are made of cast iron.

Q5. Write a short note on cupro-nickel.  

Ans.

• 1. Copper percentage in cupro-nickel alloys normally ranges from 60 to 90%. A nickel-copper alloy with a minimum 52 percent nickel content is called monel metal. 
• 2. Despite its high copper content, cupro-nickel is silver in colour. 
• 3. Because copper-nickel piping, heat exchangers, and condensers in seawater systems, as well as marine hardware, are highly resistant to corrosion by salt water, they are used in these applications.
• 4. It is occasionally applied to the hulls, shafts, and propellers of premium boats. The chemical, petrochemical, and electrical industries are some further uses.
• 5. Due to its resistance to seawater corrosion, high fabricability, and ability to reduce macrofouling levels, cupro-nickel alloys are employed in marine applications.

Q6. Discuss about some aluminium alloys and their compositions. 

Ans. Some of aluminium alloys are as follows:

a. Duralumin:

• 1. It is also known as wrought alloy of aluminium. Heat treatment and case hardening improve its tensile strength upto 400 MPa. 
• 2 It contains 3.5 % Cu, 0.5 % Mn, 0.5 % Mg and 95.5 % Al.

i. Uses:  

• 1. Due to its ability to withstand working temperatures up to 500°C, it is mostly utilised for forgings, stampings, sheets, tubes, and rivets.
• 2. Due to high strength and low weight it is mostly used in automobile and aircraft parts making.
• 3. lt is also used for manufacturing of connecting rods, bars, rivets and pulleys etc.

b. Y-alloQys:

• 1. It is an alloy of copper-aluminum. Copper increases its strength and machinability property. 
• 2. Y-alloy also contains extremely trace amounts of Si, Mg, and Fe, up to 0.6% of each. Duralumin is less strong than Y alloys at high temperatures.

i. . Uses: 

• 1. It is mostly used for casting but it may also be used in forged components. 
• 2. It is utilised to manufacture cylinder heads and pistons for aircraft engines because of its superior strength at high temperatures.

c. Magnalium: 

• 1. In the absence of air (or in a vacuum), aluminium and 2 to 10% magnesium are melted to create magnesium, which is then cooled in a vacuum or at a pressure of 100 to 200 atmn.
• 2. It also contains a very small amount of copper (approximate 1. 75 %).

i. Uses: Due to light weight and good mechanical properties, it is mainly used for manufacturing of aircraft and automobile components. 

d. Hindalium:

• 1. Hindalium is an aluminium alloy which is produced by Hindustan Aluminum Corporation Ltd., Renukoot. 
• 2. It is an alloy of aluminium and magnesium and a very small quantity of chromium. Chromium improves its non-corrosive nature. 
• 3. It is produced as a rolled product.  

i. Uses : Due to non-corrosive nature, it is used in manufacturing of utensils.

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