Metals & Metal Forms

Metal Classifications

Alkali Metals

Alkali metals are the Group 1 elements of the period table and consist of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). Elements in this group are highly reactive due to their single valence electron. The alkali metals are soft materials with relatively low melting points, and their applications typically exploit their high reactivity.

Alkaline Earth Metals

Alkaline metals are the Group 2 elements of the period table and consist of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). Because of their lower activity and affinity for their other neighbor on the periodic table, the transition metals, they have found many applications and uses in alloys to produce lighter high strength metals.

Transition Metals

The bulk of elemental metals are found within the forty transition metals which include what are commonly referred to as the base metals, such as lead iron, nickel, tin, and copper and the precious or noble metals, such as silver, gold, platinum, and iridium. They are the most abundant and easiest to mine and refine of the metal groups. Due to their ease of extraction, they were the first metals to be mined, refined and commercially used by humans. Because they are of higher density than the s-block elements, they exhibit greater strength, higher melting points, and higher density and tensile strength.

Platinum Group Metals

Platinum group metals or platinoids include six (6) transition metal elements: ruthenium, rhodium, palladium, osmium, iridium, and platinum. These elements exhibit highly catalytic properties in addition to being resistant to oxidation. They are often found together in natural mineral deposits.

Refractory Metals

Refractory metals have high heat resistance and hardness properties. Five elements frequently defined as refractory metals include niobium, molybdenum, tantalum, tungsten, and rhenium. Common features that are shared among these metals are a melting point over 2000°C and high hardness at room temperature. Due to their high melting points, these metals are creep resistant at high temperatures. Refractory metals are prone to oxidation, however, oxide layers of the bulk metals are typically limited to the surface at room temperature.

Rare Earth Elements

The seventeen (17) rare earth elements include the Group 3 elements and the Period 6 lanthanide series elements consisting of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. These metals are finding increasing uses for defense, telecommunications, and energy applications as catalysts, phosphors and polishing compounds.

Post-Transition Metals

The post-transition metals or p-block elements are extremely soft low melting metals that include the semi-liquid metals gallium and indium, tin, thallium, lead, bismuth, radioactive polonium, germanium and antimony. They are used extensively in the formation of various electronic and optical crystalline compounds.

Metalloids

Metalloids are elements that exhibit both metallic and nonmetallic properties. These elements include boron, silicon, germanium, arsenic, tellurium, antimony, polonium and astatine. While the metalloids are brittle and not used alone for structural applications, they are commonly found in alloys, glasses, and semiconductor devices.

Base metals

Base metals refer to metals that are not resistant to oxidation, tarnishing, or corrosion. Examples include copper, zinc, tin, iron, nickel, and lead.

Noble metals

Noble metals are resistant to oxidation and corrosion in air and moisture. Examples include silver, platinum, gold, osmium, and palladium. Most noble metals are also considered precious metals, as they are relatively rare and of high economic value.

Metal Production

Mining and extraction of ores

Metals production involves mining and extracting metals from their ores. Further processing is required to purify, refine, and manipulate metals to derive the final product. Processes can involve shaping, alloying, heat treatment, joining, corrosion resistance and testing of metals.

Refining, processing, casting

Refining metals involves the final purification of impure metals. This is contrast to upstream processes that extract metals from ore and require additional purification or refining to produce a highly pure finished material. Pyrometallurical and hydrometallurigal process techniques can be used in refining.

Casting involves applying molten metal into a mold. Subsequent solidification results in metal shaped to the mold. This is economical and often requires little finishing after the metal is solidified. Process parameters that determine the success of the casting process include: shrinkage due to solidification of the metal, flow rate and flow effects of molten metal into the mold, cooling rate of the metal and the mold material influence on the casting process.