Aloy

ALOY WHAT ARE ALLOYS & WHAT ARE THE AIMS OF MAKING ALLOYS ? An alloy is a partial or complete solid solution of one or more elements in a metallic matrix. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may be homogeneous in distribution depending on thermal (heat treatment) history. Alloys usually have different properties from those of the component elements. An alloy is a mixture of two or more elements in solid solution in which the major component is a metal. Most pure metals are either too soft, brittle or chemically reactive for practical use. Combining different ratios of metals as alloys modifies the properties of pure metals to produce desirable characteristics. The aim of making alloys is generally to make them less brittle, harder, resistant to corrosion, or have a more desirable color and luster. Examples of alloys are steel (iron and carbon), brass (copper and zinc), bronze (copper and tin), and duralumin (aluminium and copper). Alloys specially designed for highly demanding applications, such as jet engines, may contain more than ten elements. Aims of alloying: To increase the hardness and strength – The addition of a little carbon to iron metal produces steel which is very hard alloy of iron. – The addition of magnesium to aluminium metal produces an alloy called magnalium. Magnalium is harder than aluminium but still retains the low density of aluminium metal. – The addition of tin to copper metal produces bronze. Bronze is an alloy harder than both tin and copper. To prevent corrosion – The addition of carbon, nickel and chromium to iron metal produce stainless steel. Stainless steel ia an alloy which can resist rusting. The chromium(III) oxide and nickel(IV) oxide which prevents the iron from rusting. – The addition of tin to copper produces bronze which is able to resist corrosion and tarnish. To improve the appearance – Stainless steel is more shiny than pure iron. – Adding a little copper and antimony to tin produces the alloy pewter which is harder and shinier, and not so easily tarnished. – Alloy wheels made from aluminium and other elements improve the look of vehicles.

THE COMPARISONS OF THE PROPERTIES OF ALLOYS AND THEIR PURE METALS

EXAMPLES OF ALLOYS AND THEIR USES Carbon steel – Frameworks of buildings and bridges. – In the making of tools, framework of heavy machinery and body of vehicles. Stainless steel – In the making of cutlery and kitchenware.

In the making of machine parts and surgical instruments. Bronze – In the making of kitchenware and ships’ propellers. – In the making of decorative ornaments, statues and art crafts. Brass – In the making of electrical connectors and musical instruments. – In the making of kitchenware and decorative ornaments. Magnalium – In the making of aircraft body frames. – In the making of rims of racing car tyres. Duralumin – In the making of the bodies of aircrafts and bullet trains. – In the making of racing bicycles, fan blades, light electrical cable. Pewter – In the making of mugs, candlesticks, decorative ornaments and souvenirs. Solder – In the making of solder for electrical wires and metal pipes. Cupro-nickel – To make coins of 10 , 20 , 50 cent. –