even though aluminium is more abundant than iron in the earth's crust. And generally speaking, the more abundant a metal is, the cheaper it is
Aluminum does not show up naturally in the earth's crust, but is derived from bauxite (alumina). In order to get the metallic aluminum, a significant, expensive smelting process is involved, which requires a large amount of energy and resources. Once metallic aluminum is produced, it is easily reused, but getting the metal in the first place is difficult.
If you compact aluminium to equal strength of Iron, ALUMINIUM would weight less. if you compact aluminium to equal Weight of iron, it would be stronger then iron. it can also withstand more heat.
Because Aluminium requires an electrolytic process to obtain it from its oxide, whilst iron can be obtained from iron oxide by heating with coke in a Blast Furnace. Electricity is expensive. ...and the bauxite needs considerable purification to give alumina of a high degree of purity before it can be put into the electrolytic cell; iron ore is added directly to the Blast Furnace with no prior purification.)
Eventually its all about money. Aluminium is a better conductor of electricity than Iron, and thats the reason it is used in preference to it. For example, it would cost no more to lay an Aluminium Cable, Copper Cable or Iron cable in the ground. On overhead lines Aluminium is used because of its weight but most cables are burried. So how does it cost less when the materials are more expensive? Mainly the cable looses volts along its length and the higher its resistance it then the lower the volts are at the end of it. To keep the end users volts high enough you need shorter cables from the substations with a higher resistance cable (like Iron), and so you need many more substations. At a cost of over ?100,000 each building a substation far outweighs the extra cost of Aluminium over Iron. Also, when laying a cable in a trench the main cost is actually the civil works of digging the trench (cable at say ?45 a meter, and civil works at maybe ?100 a meter - quite a difference) There is a small consideration with the electrical resistance in the Iron. This means iron looses more energy per kilometer than an Aluminium or Copper, and this energy costs money to produce so there are savings there. Anyway, its all down to the cost of making the distribution network rather than say the weight of the cables.
AluminIum is a metal which is always found in the form of compounds minerals and ores. It is expensive because it is economically very expensive to extract from ores. It takes a lot of money and processes in chemical and manufacturing industries after which pure aluminium is obtained. One most abundant ore of aluminium is bauxite. Aluminium from it is extracted through many processes like pulverization, enrichment, conversion in metal oxide, extraction from oxide, refining etc. Also, oxide of aluminium is a very very strong and hard compound from which aluminium extraction is very hard. Though aluminium is in great abundance but what matter most is that how its purest form is extracted and sold to the users.
