The material of choice of a given era is often a defining point. Modern materials engineering evolved directly from metallurgy, which itself evolved from mining and (likely) ceramics and the use of fire. Important elements of modern materials engineering are a product of the space race: the understanding and engineering of the metallic alloys, and silica and carbon materials, used in the construction of space vehicles enabling the exploration of space. Materials engineering has driven, and been driven by, the development of technologies such as plastics, semiconductors, and biomaterials.
As a metallurgy and materials engineer with a background in materials science, I apply my understanding of the relationships between materials properties, structure, processing, and performance to:
• Develop cost-effective approaches to structural integrity.
• Characterize fracture and fatigue behavior of structures.
• Select materials and processes based on properties, cost, corrosion, and fabricability.
• Conduct failure analyses, using fracture mechanics.
• Develop customized procedures to ensure design properties at the lowest achievable cost.
The basis of materials science involves relating the desired properties and relative performance of a material in a certain application to the structure of the atoms and phases in that material through characterization. The major determinants of the structure of a material and thus of its properties are its constituent chemical elements and the way in which it has been processed into its final form. These characteristics, taken together and related through the laws of thermodynamics, govern a material’s microstructure, and thus its properties.
The engineering of materials consisting of a perfect crystal of a material is currently physically impossible. Instead metallurgists and materials engineers manipulate the defects in crystalline materials such as precipitates, grain boundaries interstitial atoms, vacancies or substitutional atoms, to create materials with the desired properties. Not all materials have a regular crystal structure. Polymers display varying degrees of crystallinity, and many are completely non-crystalline. Glasses, some ceramics, and many natural materials are amorphous, not possessing any long-range order in their atomic arrangements. The study of polymers combines elements of chemical and statistical thermodynamics to give thermodynamic, as well as mechanical, descriptions of physical properties. In addition to industrial interest, materials science has gradually developed into a field which provides tests for condensed matter or solid state theories. New physics emerge because of the diverse new material properties which need to be explained.
Advanced materials and components within my areas of expertise as a metallurgy and materials engineer include:
Advances in the engineering of materials can drive the creation of new products or even new industries. Stable industries also employ metallurgy and materials engineers to make incremental improvements and troubleshoot issues with currently used materials and processes. Industrial applications of the engineering of materials include materials design, cost-benefit tradeoffs in industrial production of materials, processing techniques (for example casting, rolling, welding, coating by ion implantation, crystal growth, thin-film deposition, sintering of powders). Much of this is accomplished through the use of analytical techniques (for example electron microscopy, x-ray diffraction, calorimetry, nuclear microscopy (HEFIB), Rutherford backscattering, neutron diffraction, and small-angle X-ray scattering (SAXS)).
Besides material characterization, the material scientist/engineer also deals with the extraction of materials and their conversion into useful forms. Thus ingot casting, foundry techniques, blast furnace extraction, and electrolytic extraction are all part of the required knowledge of a metallurgy and materials engineer. Often the presence, absence or variation of minute quantities of secondary elements and compounds in a bulk material will have a great impact on the final properties of the materials produced, for instance, steels are classified based on 1/10 and 1/100 weight percentages of the carbon and other alloying elements they contain. Thus, the extraction and purification techniques employed in the extraction of iron in the blast furnace will have an impact of the quality of steel that may be produced.
The study of metallic alloys is a significant part of materials science. Of all the metallic alloys in use today, the alloys of iron (steel, stainless steel, cast iron, tool steel, alloy steels) make up the largest proportion both by quantity and commercial value. Iron alloyed with various proportions of carbon gives low, mid and high carbon steels. An iron-carbon alloy is only considered steel if the carbon level is between 0.01% and 2.00%. For the steels, the hardness and tensile strength of the steel is related to the amount of carbon present, with increasing carbon levels also leading to lower ductility and toughness. Heat treatment processes such as quenching and tempering can significantly change these properties. Cast iron is defined as iron–carbon alloys with more than 2.00% but less than 6.67% carbon. Stainless steels are defined as a regular steel alloy with greater than 10% by weight alloying content of chromium. Nickel and molybdenum are typically also found in stainless steels.
Other significant metallic alloys are those based on aluminum, titanium, copper and magnesium. Copper alloys have been known for a long time, while the alloys of the other three metals have been relatively recently developed. Due to the chemical reactivity of these metals, the electrolytic extraction processes required were only developed relatively recently. The alloys based on aluminum, titanium and magnesium are known and valued for their high strength-to-weight ratios and, in the case of magnesium, their ability to provide electromagnetic shielding. These materials are ideal for situations where high strength-to-weight ratios are more important than bulk cost, such as in the aerospace industry and certain automotive engineering applications.