This problem (to overcome) by taking advantage of phase separation in a workable silica containing a high proportion of boric oxide.

In addition to the three crystalline forms, the element iron may (to exist) as a liquid or vapour, giving five phases overall.

The glass-reinforced polymer (to be) an example of a two-phase structure.

4. Local structural disturbances and imperfections (to disregard).

Industrial practice understandably (to favour) relatively rapid cooling rates.

The production of the thermal-shock resistant (to provide) an interesting example of the potential of phase control.

6. Join the halves of the sentences in the columns:

The term ‘phase’ refers to	a liquid or vapour.
The element iron may exist as	an example of a two-phase structure.
The important refractory oxide silica is able	a separate and identifiable state of matter in which a given substance may exist.
The glass-reinforced polymer known as Fibreglass is	to exist as three crystalline phases.

 

7. Answer the questions:

1. What does the term ‘phase’ refer to?

What do we imply when referring to a particular phase in the structure of a material?

Is it possible for two or more different phases to co-exist?

Can the production of the thermal-shock resistant provide an example of the potential of phase control?

Are glasses of very high silica content suitable for high temperature applications?

What defects may a pure metal contain?

8. Read text B and choose the best title for it:

The independent variables determining the energy state.

The Phase Rule.

A device for testing multi-phase (heterogeneous) equilibria.

Make sure that you know the following words and word combinations:

Equation – уравнение

Variable composition - переменный состав

Text B

For a given metallic or ceramic material, there is a theoretical condition of equilibrium in which each constituent phase is in a reference state of lowest energy. The independent variables determining this energy state, which are manipulated by scientists and technologists, are composition, temperature and pressure. The Phase Rule derived by Willard Gibbs from complex thermodynamical theory provides a device for testing multi-phase (heterogeneous) equilibria and deciding the number of variables (degrees of freedom) necessary to define the energy state of a system. Its basic equation, P+F=C+2, relates the number of phases present at equilibrium (P) and the number of degrees of freedom (F) to the number of components (C), which is the smallest number of substances of independently-variable composition making up the system. For metallic systems, the components are metallic elements: for ceramics, the components are frequently oxides (e.g. MgO, etc.).

 

Part II

 

1. Learn the words:

two-phase equilibria	двухфазные равновесия
solid solubility	твердая растворимость
nickel	никель
copper	медь
the intervening alloys	промежуточные сплавы
to freeze	замораживать
liquidus and solidus	ликвидус и солидус
to consider	рассматривать
solidification	затвердевание
alloy	сплав
amount	количество
manganese	марганец
ductile	пластичный
to resist	оказывать сопротивление
water treatment	очистка воды
complete	полный, абсолютный
to coincide	совпадать
fulcrum	точка опоры
Lever Rule	правило рычага
to restrict, to confine	ограничивать
adjacent to	примыкающий к
beryllium	бериллий
curving	изогнутый
solvus	сольвус
increase	увеличение
to dissolve	растворять(ся)
to quench	гасить, охлаждать

 

2. Guess the meaning of the following words and word combinations:

Metallic and ceramic systems; similarities and differences; atomic (ionic) diameter; a univariant phase; corrosion; visualize; fractions; precipitation-hardening.

3. Identify the part of speech and translate the words:

To extend, extended, extending; to illustrate, illustrated, illustration; abrupt, abruptly, abruptness; to consider, consideration; to equilibrate, equilibration; to resist, resistance, resistant; to complete; completely, completeness; to coincide, coincidental, coincidentally; to represent, representation, representative; to derive, derivative, derivation; to restrict, restriction, restrictive; to confine, confined, confinement; to preserve, preservation.

4. Match the words with their definitions:

extended and limited solid solubility	химическая и пищевая промышленность
binary phase diagram	средний состав сплава
solid solution	горизонтальные соединительные линии
melting points of the pure metals	растворимая медь
chemical and food processing	точки плавления чистых металлов
average composition of the alloy	бесконечное число
infinite number	твердый раствор
horizontal tie-lines	двоичная фазовая диаграмма
solvent copper	расширенная и ограниченная растворимость в твердом состоянии

 

Text A

Two-phase equilibria

Extended and limited solid solubility. Solid solubility is a feature of many metallic and ceramic systems, being favoured when the components have similarities in crystal structure and atomic (ionic) diameter. Such solubility may be either extended (continuous) or limited. The former case is illustrated by the binary phase diagram for the nickel–copper system in which the solid solution extends from component to component. In contrast to the abrupt (congruent) melting points of the pure metals, the intervening alloys freeze over a range of temperatures which is associated with a univariant two phase (α + liquid) field. This ‘pasty’ zone is located between two lines known as the liquidus and solidus. The phase diagrams for Ni–Cu and MgO–FeO systems are similar in form.

Let us consider the very slow (equilibrating) solidification of a 70Ni–30Cu alloy. A commercial version of this alloy, Monel, also contains small amounts of iron and manganese. It is strong, ductile and resists corrosion by all forms of water, including sea-water (e.g. chemical and food processing, water treatment). An ordinate is erected from its average composition on the base line. Freezing starts at a temperature T1. A horizontal tie-line is drawn to show that the first crystals of solid solution to form have a composition α1. When the temperature reaches T2, crystals of composition α2 are in equilibrium with liquid of composition L2. Ultimately, at temperature T3, solidification is completed as the composition α3 of the crystals coincides with the average composition of the alloy. It will be seen that the compositions of the α - phase and liquid have moved down the solidus and liquidus, respectively, during freezing.

Each tie-line joins two points which represent two phase compositions. One might visualize that a two phase region in a binary diagram is made up of an infinite number of horizontal (isothermal) tie-lines. Using the average alloy composition as a fulcrum (x) and applying the Lever Rule, it is quickly possible to derive mass ratios and fractions. In most systems, solid solubility is far more restricted and is often confined to the phase field adjacent to the end-component. A portion of a binary phase diagram for the copper–beryllium system, which contains a primary, or terminal, solid solution, is shown in Figure 3.13. Typically, the curving line known as the solvus shows an increase in the ability of the solvent copper to dissolve beryllium solute as the temperature is raised. If a typical ‘beryllium–copper’ containing 2% beryllium is first held at a temperature just below the solidus (solution-treated), water-quenched to preserve the α-phase and then aged at a temperature of 425°C, particles of a second phase (γ) will form within the α –phase matrix because the alloy is equilibrating in the (α+ γ) field of the diagram. This type of treatment, closely controlled, is known as precipitation-hardening.

 

5. Fill in the prepositions (as, of, by, for, to, in) where necessary:

1. To provide this criterion it is necessary to consider a second important property ___ state known ___ the entropy.

2. This type ___ treatment, closely controlled, is known ___ precipitation-hardening.

3. Solid solubility is a feature ___ many metallic and ceramic systems.

4. The former case is illustrated ___ the binary phase diagram ___ the nickel–copper system.

5. In contrast ___ the abrupt (congruent) melting points ___ the pure metals, the intervening alloys freeze over a range of temperatures.

6. One might visualize that a two phase region ___ a binary diagram is made up ___ an infinite number ___ horizontal (isothermal) tie-lines.

6. Join the halves of the sentences in the columns:

Solid solubility is	the binary phase diagram for the nickel–copper system.
The former case is illustrated by	a feature of many metallic and ceramic systems.
The compositions of the α - phase and liquid have	derive mass ratios and fractions.
It is quickly possible to	moved down the solidus and liquidus, respectively, during freezing.

 

7. Answer the questions: