Alloys - Full Explanation | Hindi/English ~ MONU TUTORIALS ACADEMY

Introduction

Definition : an alloy is a solid mixture of two or more elements one of which must be a metal. In other words, an alloy is a solid mixture of metal with other metal or some nonmetal. The constituent in definite ratio are melted together and then allowed to cool to form a solid material called an alloy. For example, brass is an example of of copper and zinc.

the metal having the largest proportion in the alloy is known as the base metal and other element which are added to get desired properties in the alloy are called alloying elements.

Alloy containing Mercury as one of the component are known as amalgams full stop this are prepared by treating metal like sodium zinc gold with Mercury.

Necessity of making alloys

the alloy are prepared to modify certain physical properties of metal and to develop some useful properties which the individual components metal do not possess. Following of metal is generally done to achieve the following:

To increase hardness

the hardness of the metal can be increased by alloying it with other metal or some nonmetal, e.g. pure gold is too soft for making jewellery. Thus, it is hardened by alloying with copper. Steel, which is an alloy of iron and carbon is harder than pure iron.

To increase the corrosion resistance of metal

metal such as iron copper are when exposed to the atmosphere get corroded by the surrounding gases and moisture.to protect them from corrosion this matter are generally alloyed with other materials as a lawyer highly resistant to corrosion.

To lower the melting point

The melting point of some alloy such as solder are lower than any of the constitutes. Thus, alloying of metal makes them easily fusible.

To increase the tensile strength

Alloying of metals generally increase the tensile strength of base 1000 kam magnalium an alloy of magnesium and Aluminium, has greater tensile strength1000 kam magnalium, and alloy of magnesium and Aluminium, has greater tensile strength than magnesium and Aluminium.

To increase or decrease Melleability and ductility

malleability and ductility of metal can be varied by allowing it with some other metals, e.g. copper can be made less time by alloying it with zinc. Nickel Steel used for making automobile and aeroplane parts can be made by alloying Steel with nickel.

To produce good casting

To get a good casting from metal must expand on solid ification. Pure metal generally undergo construction on solid fixations. Therefore, metals are alloy to get good casting.

To modify colour

the colour of matter can be modified by allowing it with another suitable metal. For example, branch, used for making statue is prepared by alloying copper with tin.

To increase conductivity

Electrical conductivity of metal can be enhanced by making alloy with another metal, e.g. duralumin,an alloy of aluminium with copper and magnesium and manganese is used for Keval making due to its high electric conductivity.

Classification of alloys

The alloy may be classified into two main types,

Ferrous alloys
Non ferrous alloys

1. Ferrous alloys

the alloy which contain iron as one of the major component are known as ferrous alloys. Alloy Steel are the most important ferrous alloy.alloy Steel are prepared by adding certain metal or nonmetal to steel. Some of the important alloy Steel are.

Chromium Steel
Nickel Steel
Nickel chromium Steel
Cobalt Steel
Tool Steel

2. Non ferrous alloy

these alloy do not contain iron as one of the main component but contain non ferrous metal such as copper, Aluminium,lead and tin.some common non ferrous alloy are brass and gunmetal. this alloy generally have lower melting points than ferrous alloys. they generally have good and attractive colours special electrical properties, low coefficient of friction low density and corrosion resistance properties.

Preparation of alloy

The method most commonly employed for the manufacture of alloy are:

Fusion

This is the most frequently used method for the preparation of alloy the component in the desire proportion are fused together in a crucible. The component metal have highest melting point is first melted and then the component having lower melting points are added to eat. The molten mass is throughly stirred to get a uniform mixture. The surface of the molten mass is usually covered with the carbon layer to prevent the oxidation of the components.

Electrodeposition

in this method coma the component metal are deposited from the electrolyte containing their solution by the process of electrolysis. Brass which is an alloy of copper and zinc is obtained by the electrolysis of solution of copper and zinc cyanides dissolved in potassium cyanide.

Reduction

when a metallic compound is reduced by another metallic component and a lower of the two metal is formed. For example,aluminium bronze is prepared by heating Aluminium oxide with copper in the presence of carbon in an electric furnace.

Compression aur power metallurgy

in this method comedy the finely divided components are mixed together in right proportion and mechanically compressed under high pressure and temperature and the alloys formed. Analogue and Nico is obtained by compressing a mixture of powdered aluminium nickel and Cobalt.

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