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Lesson 2 engineering materials

Task 1. Look at the title of the unit and list the materials you know which are used in engineering. Discuss your list with a partner.

Task 2. Read the text (reading time is 8 minutes) and answer the following questions:

1. How did man learn to obtain metal from stone?

2. What do we call the age which followed the Bronze Age?

3. Why do scientists consider metals to be the most useful in the form of alloys?

4. Can an alloy have properties which no metal in nature has?

Metals and alloys

Everybody knows that metals and alloys play important part in any branch of technique as well as in our everyday life. But when did man come to know them? How early were metals and alloys used by man?

From the earliest times man has made things of materials obtained from the earth. For thou­sands of years of the Stone Age for making tools he used mostly stone. Then came the disco­very that metal can be produced from certain types of stones when they were treated with fire. By heating stones to very high temperatures man made the metal the stones contained melt and run out of them. Sometimes, as we know it now, man had to add some carbon (C) to produce compounds of metals. We know also copper (Cu) and tin (Sn) to be two of the earliest metals obtained this way. Then man noticed that the two metals, when melted together, produced a new material that was much harder and stronger than either of them had been. Scientists think this discovery opened a new period in man's development. Since the discovery the period to continue for about seven hundred years is considered to be the age of bronze. That's why the scientists gave it the name of the Bronze Age. It had lasted for about 700 years when came the time when man learned to produce iron, which became one of the most important metals for him. It marked the beginning of a new age - the Iron Age.

Since then man has learned how to produce a lot of other metals and how to obtain thousands of alloys from them. To produce an alloy man melted together two or more metals. As the time passed many different types of alloys were discovered. Now we know some alloys to contain not only metals but also non-metals, such as carbon, sulphur (S), phosphorus (Ph), etc. Gene­rally speaking, it is in the form of alloys that one considered metals to be the most useful. A lot of metals are converted into alloys of much importance and scientists and metallurgists want much more new alloys to serve man's needs. We want you to know that only about as little as 30 metallic elements serve modern needs of man, but there are over five thousand alloys, hundreds of which are in common use. So many different alloys have been elaborated because modern industry requires metals to be used for different purposes.

We know scientists to classify all the alloys into some types or classes according to their chemical composition and physical properties. According to composition, all the alloys are to be classi­fied as ferrous alloys (those containing iron) and non-ferrous ones (those containing no iron or only a small quantity of it). The classes of alloys based upon their physical properties inclu­de light-weight alloys, low melting-point alloys and others.

An alloy to answer the purpose it has been elaborated for is to have certain properties or certain combination of properties which no metal in nature has. Many industries need alloys having certain chemical and physical properties. For example, new kinds of stainless steel are being designed to resist the action of acids and corrosion due to the atmospheric agents under high temperatures. Some of the alloys to be used in the automobile engines are to withstand very high temperatures. Future improvements in gas turbines depend in large measure on the development of new improved heat-resisting alloys too. In the nearest future we expect metallurgists to elaborate new ways of controlling both chemical and physical properties of alloys and elaborating many new ways of important alloys for our technique and economy.

Task 3.Fill the gap.

1. To produce (…) man melted together two or more metals.

2. Now we know some alloys to contain (…) such as sulphur, phosphorus, etc.

3. According to composition, all the alloys are to be classified as (…) ones.

4. The classes of alloys based on their physical properties include (… …) alloys and others.

5. New kinds of (…) steel are being designed to resist the action of acids and corrosion.

Task 4. Study the table and choose the most useful material from your point of view. Give grounds.

Materials	Properties	Uses
Metals Aluminium	Light, soft, ductile, highly conductive, corrosion-resistant	Aircraft, engine components, foil, cooking utensils
Copper	Very malleable, tough and ductile, highly conductive, corrosion-resistant	Electric wiring, PCBs, tubing
Brass (65% copper, 35% zinc)	Very corrosion-resistant. Casts well, easily machined. Can be work hardened. Good conductor	Valves, taps, castings, ship fittings, electrical contacts
Mild steel (iron with 0.15% to 0.3% carbon)	High strength, ductile, tough, fairly malleable. Cannot be hardened and tempered. Low cost. Poor corrosion resistance	General purpose
High carbon steel (iron with 0.7% to 1.4% carbon)	Hardest of the carbon steels but less ductile and malleable. Can be hardened and tempered	Cutting tools such as drills, files, saws
Thermoplastics ABS	High impact strength and toughness, scratch-resistant, light and durable	Safety helmets, car components, telephones, kitchenware
Acrylic	Stiff, hard, very durable, clear, can be polished easily. Can be formed easily	Aircraft canopies, baths, double glazing
Nylon	Hard, tough, wear-resistant, self-lubricating	Bearings, gears, casings for power tools
Thermosetting plastics Epoxy resin	High strength when reinforced, good chemical and wear resistance	Adhesives, encapsulation of electronic components
Polyester resin	Stiff, hard, brittle. Good chemical and heat resistance	Moulding, boat and car bodies
Urea formaldehyde	Stiff, hard, strong, brittle, heat-resistant, and a good electrical insulator	Electrical fittings, adhesives

Task 5. Look through the table again. Fill in the chart and find a material which has the following properties.

Properties	Material(s)
soft
ductile
malleable
tough
scratch-resistant
conductive and malleable
durable and hard
stiff and brittle
ductile and corrosion-resistant
heat-resistant and chemical-resistant

Task 6. What are these made of? Match the photos with these materials.

aluminum ceramic fiberglass nylon rubber steel titanium graphite polycarbonate

1_________________________

2___________________

3_____________________

4_________________________	5__________________	6_____________________
7_________________________	8__________________

Task 7. Study the following text about aluminium.

Aluminium is used to make aircraft, engine components, and many items for the kitchen.

We can add extra information to the text like this:

Aluminium, which is light, soft, and ductile, is used to make aircraft, engine components - for example, cylinder heads - and many items for the kitchen, such as pots.

Note that the extra information is marked with commas or dashes:

, which

-for example,... -

, such as ...,

Task 8. Add this extra information to the following text about plastics.

1. Plastics can be moulded into plates, car components, and medical aids.

2. Thermoplastics soften when heated again and again.

3. Thermosetting plastics set hard and do not alter if heated again.

4. ABS is used for safety helmets.

5. Nylon is self-lubricating.

6. Nylon is used for motorized drives in cameras.

7. Acrylic is a clear thermoplastic.

8. Acrylic is used for aircraft canopies and double glazing.

9. Polyester resin is used for boat and car bodies.

10. Polyester resin is hard and has good chemical and heat resistance.

Plastics are synthetic materials. They can be softened and moulded into useful articles. They have many applications in engineering. There are two types of plastics: thermoplastics and thermosetting plastics.

ABS is a thermoplastic which is tough and durable. Because it has high impact strength, it has applications where sudden loads may occur.

Nylon is a hard, tough thermoplastic. It is used where silent, low-friction operation is required.

Acrylic can be formed in several ways. It is hard, durable, and has many uses.

Polyester resin is a thermosetting plastic used for castings. It has a number of useful properties.

Task 9. Watch the video “Advanced Engineering Materials - Metal foams by North Carolina State University” and answer the questions – What are the properties of metal foams? Where are they used?

Task 10. Prepare a presentation on any material, its properties and usage.