Are the following statements true or false?

1 The term ‘yield point’ is applicable only to low-carbon steels.

2 Ductility denotes the capacity to be drawn from a larger to a smaller diameter of wire.

3 Brittleness means the capacity to be rolled or hammered into thin sheets.

4 Often ductile metals are brittle.

5 Hardness may be defined as resistance to indentation.

6. Answer the questions:

What point of stress-strain curve does yield point refer to?

What grades of steels is yield point applicable to? Why?

What characteristics are used as a measure of the ductility of the metal?

What property of metal is characterized by toughness?

Which test is commonly used to measure toughness?

What properties does a malleable metal possess?

Is there a difference between malleability and ductility?

How does brittleness correlate with toughness and ductility?

9 What does ‘alternation of stress’ mean?

Why is hardness difficult to define?

How is hardness usually characterized and why?

SECTION II

Unit I. PRINCIPLES AND APPLICATIONS OF PHASE DIAGRAMS

Part I

1. Learn the words:

to refer	относиться
separate	отдельный
identifiable	опознаваемый
substance	вещество
to exist	существовать
applicable to	применимый к
to provide	предоставлять
convenient	удобный
in addition to	в дополнении к
iron	железо
refractory oxide silica	огнеупорный оксид кремния
tridymite	тридимит
cristobalite	кристобалит
silica glass	кварцевое стекло
molten silica	расплавленный кремнезем
glass-reinforced polymer	армированный стекловолокном полимер
fibreglass	стекловолокно
bounding surface	ограничивающая поверхность
contiguous phase	непрерывная фаза
structural disturbances and imperfections	структурные нарушения и недостатки
an oxide solid solution	твердый раствор оксида
by convention	условно
voids	пустоты
rapid cooling rates	скорость быстрого охлаждения
equilibrium	равновесие
annealing of metals and alloys	отжиг металлов и сплавов
structural heterogeneity	структурная неоднородность
high silica content	высокое содержание кремнезема
boric oxide	оксид бора
a porous siliceous matrix	пористая кремниевая матрица
withstand quenching	выдерживать закалку

 

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

Microdefects; grain boundaries; metastable condition; ‘triggering’ process; nonequilibrium; scientific difficulty; high temperature applications; to be heat-treated; separation of two phases; electron microscopy; boron-rich phase; skeletal structure; a low linear coefficient; thermal expansion; iced water; maximum service temperature.

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

To separate, separation, separately; to identify, identification, identifier; to exist, existence, existing; to apply, application, applicable; to provide, provider, providing; to differentiate, differentiation, differential; to imply, implied, implicit; to reveal, revealing; to surround, surrounded, surroundings; consolidate, consolidation; to refer, reference; to express, expression, expressed; to add, additional, addition; to comprise, comprising; to disturb, disturbance, disturbed.

4. Match the words with their definitions:

the concept of a phase	чистый металл
crystalline and non-crystalline materials	тепловая активация
way of expressing	термостойкий
exist as a liquid or vapour	вязкость
a pure metal	процесс изготовления
thermal activation	существовать в виде жидкости или пара
thermal-shock resistant	способ выражения
viscosity	кристаллические и некристаллические материалы
fabrication process	концепция фазы

 

Text A

The concept of a phase

The term ‘phase’ refers to a separate and identifiable state of matter in which a given substance may exist. Being applicable to both crystalline and noncrystalline materials, its use provides a convenient way of expressing a material’s structure. Thus, in addition to the three crystalline forms, the element iron may exist as a liquid or vapour, giving five phases overall. Similarly, the important refractory oxide silica is able to exist as three crystalline phases, quartz, tridymite and cristobalite, as well as a non-crystalline phase, silica glass, and as molten silica. Under certain conditions, it is possible for two or more different phases to co-exist. The glass-reinforced polymer (GRP) known as Fibreglass is an example of a two-phase structure. When referring to a particular phase in the structure of a material, we imply a region comprising a large number of atoms (or ions or molecules) and the existence of a bounding surface which separates it from contiguous phases. Local structural disturbances and imperfections are disregarded. Thus, a pure metal or an oxide solid solution are each described, by convention, as single-phase structures even though they may contain grain boundaries, concentration gradients (coring) and microdefects, such as vacancies, dislocations and voids. Industrial practice understandably favours relatively rapid cooling rates, frequently causing phases to exist in a metastable condition. Some form of ‘triggering’ process, such as thermal activation, is needed before a metastable phase can adopt the stable, or equilibrium, state of lowest energy (e.g. annealing of metals and alloys). These two features, structural heterogeneity on a micro-scale and nonequilibrium, do not give rise to any untoward scientific difficulty.

The production of the thermal-shock resistant known as Vycor provides an interesting example of the potential of phase control. Although glasses of very high silica content are eminently suitable for high temperature applications, their viscosity is very high, making fabrication by conventional methods difficult and costly. This problem was overcome by taking advantage of phase separation in a workable silica containing a high proportion of boric oxide. After shaping, this glass is heat-treated at a temperature of 500–600°C in order to induce separation of two distinct and interpenetrating glassy phases. Electron microscopy reveals a wormlike boron-rich phase surrounded by a porous siliceous matrix. Leaching in hot acid dissolves away the former phase, leaving a porous silica-rich structure. Consolidation heat-treatment at a temperature of 1000°C ‘shrinks’ this skeletal structure by a remarkable 30%. This product has a low linear coefficient of thermal expansion and can withstand quenching into iced water from a temperature of 900°C, its maximum service temperature.

 

5. Open the brackets and put the predicate in the correct form, translate the sentences: