4.19. In the above text, find the English equivalents for the following words and word combinations:

около двадцати, вместе взятые, имеет более разнообразные механические свойства, применяются в атомной энергетике, является наиболее востребованной, большая часть, используется в электротехнике, принимается во внимание в первую очередь (является важным фактором), для повышения прочности, для изготовления искусственных драгоценностей и художественного литья, стоят дороже стали и уступают ей по прочности, присущие только им, корпус двигателя

4.20. Read the text and write a list of titanium and its alloys qualities that make titanium different from other metals. A wonder metal

The first recorded hip-joint replacement was done as far back as 1897 and it was a hazardous business. The operation is now a routine piece of surgery. However, the requirements to the implant are very stringent. It has to take large loads without bending. Body fluids are as corrosive as sea water, so the implants must be designed against stress corrosion and corrosion fatigue. The metal must be bio-compatible. And, ideally, it should be light as well. The materials that best meet these tough requirements are based on titanium.

Titanium, a metal element with a melting point of 1675ºC, an atomic weight of 47.9, and a density of 4.5g/cm³, has often been referred to as the “wonder” metal. The story of titanium is extraordinary. To begin with, it was discovered twice. A British scientist, William Gregor, found it first and called it menachanite. Six years later, in 1797, M.H. Klaproth, a German chemist, also found it and gave it the name “titan”.

For many years titanium was of interest only to research chemists: it was considered too brittle to be of any practical value. Yet it was the impurities that made it brittle. It cost the chemists in many countries endless efforts to isolate pure titanium and to start producing it commercially.

A group of Soviet researchers led by Professor I. Kornilov produced a shape-memory alloy. The following experiment shows: a thin bent strip of the new titanium-nickel alloy was clamped to a stand, a 500-g weight hung on the free end. A current was passed through for several seconds, which heated the strip to more than 100ºC. As if commanded by an enigmatic force, it straightened out like a tight spring and lifted the load. When the current was switched off, the strip gradually went back to its original shape. The cycle was repeated a number of times, and the strip always “remembered” its original shape.

Besides, titanium shows special acoustic properties. At room temperature, the alloy called titanium nickeloid becomes soft, ductile and does not produce the characteristic metallic sound when struck. However, when it is heated to a certain temperature, it becomes hard, resilient and ringing.

The above titanium’s excellent resistance to most environments is the result of its stable protective surface film. This film forms naturally and consists basically of TiO₂.

Titanium is the fourth most abundant structural metal in Earth’s crust behind Al, Fe, and Mg. It is applied in making ships, aircraft, cars, bridges, turbines, tubings and heat exchangers. However, the major use of titanium, as TiO₂, is a pigment “whitener” in paints, paper, rubber, plastics, and the like at about 20× the use level of metallic titanium.

All in all, titanium in its natural form is a dark grey metal. However, it is easily anodized to give a very attractive array of colours leading to use in jewellery and various applications where appearance is important.

Notes

hip joint – тазобедренный сустав

hazardous a – опасный, рискованный

implant n – имплантат

stringent a – строгий, жесткий

bio-compatible a – биологически совместимый

tough requirements – жесткие требования

shape-memory alloy – сплав с эффектом памяти формы

enigmatic a – загадочный, таинственный

straighten out v – выпрямляться

resilient a – упругий

environment n – (окружающая) среда

heat exchanger – теплообменник

anodize v – анодировать, окислять электролитически

4.21. Complete the following text with the words from the word list:

affected, are, bottom, combination, converting, electric, eventually, into, lining, point, than, transformed

An electrolytic process is used for (1) …… the alumina powder (Al₂O₃) into aluminium. The alumina is liquefied inside a furnace and a strong (2) …… current is passed through it. The current separates the alumina into aluminium and oxygen molecules.

The oxygen molecules (3) …… attracted to the carbon anodes in the furnace. The anodes are slowly oxidized and (4) …… into carbon monoxide gas (CO). They are (5) …… replaced with new anodes.

The electric furnaces are generally rectangular steel containers. The sides and the bottom have a thick carbon (6) …… forming the cathode. The anodes are large blocks of carbon. The electrolyte is a mixture of alumina and cryolite. Cryolite is a chemical (7) …… of aluminium, sodium and fluorine. It is used to lower the melting (8) …… of the alumina from approximately 2000ºC to about 1000ºC. The cryolite is not (9) …… by the electric current but the alumina is converted (10) …… aluminium and oxygen. The pure aluminium is heavier (11) …… the cryolite mixture and so it sinks to the (12) …… of the furnace. It runs into containers and is solidified into blocks. More alumina is added to the mixture and the refined aluminium is removed.

Notes

refining n – очистка, рафинирование lining n – обкладка, облицовка

alumina n – окись алюминия fluorine n – фтор

4.22. The table of common non-ferrous metals below gives their most important properties and their uses. Read the example and make paragraphs about the other alloys in the same way.

Alloy	Composition	Important Properties	Uses
Aluminium bronze	95% Cu, 5% Al	good durability, golden colour	cigarette boxes, etc.
Duralumin	95% Al, 4% Cu	light and strong	girders, tubes
Nichrome	80% Ni, 20% Cr	high m.p., high electrical resistance	fire elements
Bronze	90% Cu, 10% Al	good durability	coins, statues
Brass	67% Cu, 33% Al	good durability	ship parts
Phosphor bronze	89% Cu, 10% Sn (0.3% P)	hard and elastic	springs
Leaded brass	66% Cu, 33% Zn (1% Pb)	soft and ductile	screws, nuts, bolts
Monel metal	70% Cu, 25% Ni	non-magnetic	ship parts

Example:

Aluminium bronze contains approximately 19 times as much copper as aluminium. It is used for manufacturing cigarette boxes etc. because it has good durability and a golden colour.

4.23. Read and analyze the text to give headings to each of its five paragraphs.