Montshire Minute: Alloys

Originally aired during the week of December 9, 2002

Monday

Superman is faster than a speeding bullet, more powerful than a locomotive, and can leap tall buildings in a single bound. But can his body withstand the numbing cold of outer space, or survive the fiery descent when he breaks through the atmosphere? If he truly is the man of steel, than Superman himself would wilt under these pressures. You see, steel is strong, but to create a spacecraft you also need a material that is lightweight and can withstand very hot or cold temperatures. Nature hasn't created natural reservoirs of a metal that can do all of these things. But we can combine the ingredients nature has provided, in just the right measure, to make metals that can do all these things. These mixtures of metals are called alloys. With apologies to Superman, alloys are even resistant to kryptonite!

Tuesday

To create a spacecraft, we need a material that is strong and lightweight, and that can withstand great extremes in temperature. Special alloys - combinations of metals - can be created to meet all these requirements. Alloys of aluminum and titanium are important in the aerospace industry because they are strong and light. To resist the heat generated during reentry into the earth's atmosphere, alloys containing tungsten, cobalt, or nickel are useful. Special alloys have been developed to meet hundreds of other needs. Copper, nickel, and titanium alloys do a good job of preventing the corrosive effects of salt water, so alloys from these metals are used in desalination plants. Because metals make up about three-fourths of all the elements in the periodic table, there are a great many metallic recipes we could cook up.

Wednesday

Steel is so strong and versatile, it is used in countless ways for many different building jobs. But you don't find steel on the periodic table of elements. That's because steel is an alloy, or a mixture of elements. Steel is made of iron and carbon, and the secret of its making is hard earned knowledge, won from thousands of years of messing around with molten metals. Actually there are many different kinds of steel. An alloy with high carbon content makes very hard, brittle steel. Stainless steel found in razor blades, surgical instruments and silverware (oops! I mean flatware) also may contain manganese, sulphur, chromium, or other elements.

Thursday

Discovering bronze was so important to the advance of civilization that a whole historical epoch was named for it. It still isn't clear exactly how humans figured out how to make bronze thousands of years ago. The secret may have been revealed by accident. Our ancestors may have observed how certain rocks rich in copper and tin formed bronze when heated. Bronze is stronger and harder than most alloys except steel, and it does not break easily under stress. It also resists rust and can be shaped into many different forms through molding or casting. In cultures all over the world, bronze was used for tools, weapons, and beautiful objects like jewelry. Today we have developed many other alloys, but we still use bronze for household items like doorknobs and drawer handles, to engine parts, bearings, and wire.

Friday

Some metals like copper, silver, and gold have electrons that tend to stick very close to the nucleus of the atom. It is very difficult to pry these electrons away to create new compounds. So gold and silver are found mostly in pure states, widely dispersed through the earth's crust. Since gold is found mostly uncombined with other elements, early goldsmiths learned to collect small fragments of this precious metal and then weld them together by hammering. Silver is the most chemically active of the noble metals, harder than gold but softer than copper. Because they are so resistant to reaction, gold, silver and copper are perfect materials for things that need to stable for a long time, like coins, dental crowns and electronic wire. Gold can be alloyed with nickel to create "white gold" so prized by jewelers.