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metals are materials most widely used in industry because of their properties. the study of the production and properties of metals is known as metallurgy.
the separation between the atoms in metals is small, so most metals are dense. the atoms are arranged regularly and can slide over each other. that is why metals are malleable (can be deformed and bent without fracture) and ductile (can be drawn into wire). metals vary greatly in their properties. for example, lead is soft and can be bent by hand, while iron can only be worked by hammering at red heat.
the regular arrangement of atoms in metals gives them a crystalline structure. irregular crystals are called grains. the properties of the metals depend on the size, shape, orientation, and composition of these grains. in general, a metal with small grains will be harder and stronger than one with coarse grains.
heat treatment such as quenching, tempering, or annealing controls the nature of the grains and their size in the metal. small amounts of other metals (less than 1 per cent) are often added to a pure metal. this is called alloying (легирование) and it changes the grain structure and properties of metals.
all metals can be formed by drawing, rolling, hammering and extrusion, but some require hot-working. metals are subject to metal fatigue and to creep (the slow increase in length under stress) causing deformation and failure. both effects are taken into account by engineers when designing, for example, airplanes, gas-turbines, and pressure vessels for high-temperature chemical processes. metals can be worked using machine-tools such as lathe, milling machine, shaper and grinder.
the ways of working a metal depend on its properties. many metals can be melted and cast in moulds, but special conditions are required for metals that react with air.
metals
metallurgy
most metals
the regular arrangement of atoms in
irregular
the properties of the metals
metals with small grains will
the nature of the grains in the metal.
alloying
all metals can be formed
creep
metals can be worked
Gorilla is the largest of all apes. Its height is around 1,75 metres and its weight is around 180 kg. Its body is covered with dark hair. Gorillas have a massive body structure with well-developed muscular system. Despite their threatening look they are quite peaceful creatures. They usually do not attack others, however, if needed they will stand up for their troop.
Gorillas live in groups. The leader of the group is the oldest adult male. Adult male is responsible for movement decisions, looking for a place to spend the night and organising daily routine of the troop. Gorillas are very caring parents to their offsprings.
Gorillas are herbivorous animals. Sometimes they can also feed on nuts and fruits. They rarely drink water, because plants contain sufficient amount of it.
Chest-beating is a well-known characteristic feature of gorillas. However, this is mostly used for threatening and rarely indicates that a gorilla is going to attack. The gesture symbolizes all the power and strength of this animal. Sometimes when a gorilla is really infuriated, it can bite.
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