Question

advantage and disadvantage of alloys

Answer 1

They are usually harder and stronger, e.g. bronze and brass are harder and stronger than copper, tin or zinc, and vanadium added to iron makes for a stronger ad more heat-resistant steel. Gold is allowed with silver and copper to make jewelry, because pure 24kt gold is too soft. Often they are more resistant to oxidation, e.g. adding chromium to iron makes "stainless" steel, in which the chromium forms a passivating protective layer on the surface that protects the iron from oxidation (rusting).

Some alloys have unusual and useful magnetic, electronic, or chemical properties, e.g. aluminum, nickel and cobalt ("alnico") make an unusually good ferromagnetic material, as do allows of some of the rare earths (neodymium and samarium) with some of the metals near iron. A widely used catalyst for hydrogenation in industrial chemistry is "Raney nickel," which is prepared from a alloy of nickel and aluminum.

On the other hand, alloys are usually less ductile and malleable, i.e. more brittle. It can be tricky to control the mixing and exact composition during manufacture, and failure to do so can lead to poor material properties, e.g. a propensity to fracture along grain boundaries. And, of course, an alloy is rarely cheaper than the cheaper of the metals you are mixing, e.g. stainless steel costs more than plain steel. An exception would be something like gold, which is actually cheaper when alloyed with silver, but more expensive when alloyed with platinum.