Steel and the Birth of Alloy Engineering

By Taha KhanReviewed by Frances BriggsFeb 16 2026

In many ways, steel laid the foundation of materials science. And when scientists discovered that combining different metals could create interesting properties, steel was among the first of these materials to be engineered successfully. Its development reshaped industries, transportation, and construction.

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First There Was Iron, Then There Was Steel 

Iron has been used by human civilizations for over three millennia. The Iron Age saw the popularization of ironworking, as blacksmiths learnt to heat, hammer, and shape the metal into tools, weapons, and more.

However, early iron production relied solely on furnaces, generating relatively pure wrought iron with low carbon content. Although it was malleable, wrought iron lacked the hardness and strength required for many applications.

This wrought iron was a few steps from steel. Steel, technically, is described as an alloy of iron and carbon containing less than 2 % carbon and 1 % manganese and small amounts of silicon, phosphorus, sulphur, and oxygen. The addition of carbon alters iron’s microstructure in a way that its hardness and tensile strength are increased and its ductility is reduced. 

Ancient smiths occasionally produced steel unintentionally by exposing iron to carbon-rich environments during forging. Over time, techniques such as carburization allowed craftspeople to create harder surface layers on iron tools. ^{1, 2}

One of the earliest high-quality steels was produced by crucible steelmaking, a method developed in various places, including India. Wootz steel, known for its distinctive microstructure and mechanical performance, became valued and was used to create Damascus blades. ^{1, 2}

The Bessemer Process

Image Credit: Irene Miller/Shutterstock.com

Steel's big moment came in the 19th century, when the limits of iron started to become apparent. Railways, bridges, and fast-moving machinery driving the Industrial Revolution needed stronger and more reliable structural materials. Although iron was still widely used, it was too brittle and too soft for expanding rail networks, bridges, and machinery.

In 1856, Henry Bessemer changed the economics and the reliability of steelmaking with a deceptively simple technique. The Bessemer process involved blowing air through molten pig iron to oxidize and remove impurities such as carbon, silicon, and manganese.

Manufacturers could now steer the production process, forming steel with consistent and tunable properties by controlling the decarburization process.

On top of this, Bessemer’s method allowed, for the first time, the deliberate control of steel composition on an industrial scale. This allowed engineers to tailor material properties to specific applications, such as structural beams that demanded both strength and flexibility. ^{3, 4}

Open-hearth and basic oxygen steelmaking later expanded control over composition and quality, building on the same core idea: Steel is transformative when it is strong, repeatable, and spec-driven.

Alloying Elements and Property Control

As metallurgists gained a better understanding of steel chemistry, they discovered that adding other elements could further refine material performance. This was the beginning of alloy engineering as a scientific discipline.

Elements such as chromium, nickel, molybdenum, and vanadium were introduced to improve specific characteristics.

For instance, chromium enhances corrosion resistance and forms the basis of stainless steel. Nickel improves toughness and impact resistance, particularly at low temperatures. Molybdenum increases high-temperature strength, and vanadium refines grain structure and enhances wear resistance. ^{5, 6}

These alloying additions allowed engineers to design steels for highly specialized applications: Stainless steels improved food processing, medical instruments, and the chemical industries by providing resistance to corrosion and contamination.

High-strength low-alloy (HSLA) steels enabled lighter yet stronger structural components, improving fuel efficiency in transportation and reducing material usage in construction. ^{7, 8}

Moreover, the ability to manipulate microstructure through heat treatment further expanded steel’s versatility. Quenching, tempering, and annealing allowed engineers to control phase transformations between ferrite, austenite, and martensite. These transformations directly influence hardness, toughness, and fatigue resistance.

Steel as a Platform for Scientific Metallurgy

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The development of steel coincided with major advances in scientific metallurgy.

During the late 19th and early 20th centuries, researchers began applying thermodynamics and crystallography to understand metal behavior at the atomic level.

The iron-carbon phase diagram became a tool for metallurgists to illustrate how temperature and composition influence microstructure. This diagram provided a predictive framework for how steel would respond to heating, cooling, and alloying.

The study of dislocations and defects within crystal lattices improved the understanding of mechanical behavior. Researchers recognized that strengthening mechanisms, such as solid-solution strengthening, precipitation hardening, and grain refinement, could be systematically applied to enhance performance.  ^{1, 3, 9}

High-Entropy Alloys

Traditional alloys are usually based on a dominant element with smaller additions of others. Modern materials research has introduced a different concept of high-entropy alloys (HEAs) that consist of multiple principal elements mixed in near-equal proportions. The concept emphasizes configurational entropy as a stabilizing factor.

High-entropy alloys usually form simple solid-solution phases despite their complex composition. This unique structure can provide excellent mechanical strength, thermal stability, and corrosion resistance.

Some HEAs demonstrate high performance under extreme conditions, including cryogenic temperatures and high-stress environments. Researchers are exploring their potential for aerospace, nuclear energy, and advanced manufacturing applications. ¹⁰

Click this link to read all about the latest in modern steel engineering.

The Steel We Know Today

With the rise of steel engineering, this metal alloy became a programmable substance. That is clearly reflected in today's research, where computational methods, lower carbon routes, and testing for performance under extremes are narrowing the gap between research and industry performance.  

References

1. Erb-Satullo, N. L. (2019). The innovation and adoption of iron in the ancient Near East. Journal of Archaeological Research. DOI:10.1007/s10814-019-09129-6, https://link.springer.com/article/10.1007/s10814-019-09129-6
2. Agasti, N., & Pani, B. (2023). Chemistry of ancient materials of iron in India. Applied Surface Science Advances. DOI:10.1016/j.apsadv.2023.100456, https://www.sciencedirect.com/science/article/pii/S266635112300456
3. Bodsworth, C. (2024). The Bessemer Process in the North West of England. In Sir Henry Bessemer. CRC Press. DOI:10.1201/9781003580027-4, https://www.taylorfrancis.com/chapters/edit/10.1201/9781003580027-4/bessemer-process-north-west-england-bodsworth
4. Ebiware, D. E., Salawu, A. O., & Mohammed, A. N. (2025). An overview of the development of contemporary steel making processes. International Journal of African Innovation and Multidisciplinary Research. DOI:10.70382/mejaimr.v7i2.033, https://doi.org/10.70382/mejaimr.v7i2.033
5. Liao, X., Zheng, Z., Liu, T., Long, J., Wang, S., Zhang, H., & Zheng, K. (2024). Achieving high impact–abrasion–corrosion resistance of high–chromium wear–resistant steel via vanadium additions. Journal of Materials Research and Technology. DOI:10.1016/j.jmrt.2024.02.015, https://doi.org/10.1016/j.jmrt.2024.02.015
6. Peral, L. B., Fernández-Pariente, I., Colombo, C., Rodríguez, C., & Belzunce, J. (2021). The positive role of nanometric molybdenum–vanadium carbides in mitigating hydrogen embrittlement in structural steels. Materials. DOI:10.3390/ma14237269, https://www.mdpi.com/1996-1944/14/23/7269
7. Luo, L., Zhang, J., Fu, H., Chen, F., Qin, J., & Li, Y. (2024). Effects of partially replacing Mo with Nb on the microstructure and properties of high-strength low-alloy steel during reverse austenization. Metals. DOI:10.3390/met14080896, https://www.mdpi.com/2075-4701/14/8/896
8. Mazini, J. P., Itman Filho, A., Ávila, B. M. R., Silva, R. V. D., & Oliveira, P. G. B. D. (2022). Microstructure and mechanical properties of microalloyed steels containing molybdenum. Materials Research. DOI:10.1590/1980-5373-MR-2021-0608, https://www.scielo.br/j/mr/a/10.1590/1980-5373-MR-2021-0608
9. Zhang, W. B., Gu, Z. W., Yang, H. Y., Dong, B. X., Chang, F., Wang, B. B., & Jiang, Q. C. (2026). Research Progress on Strengthening Mechanisms and Application of High-Performance Cold-Work Tool and Die Steels. Journal of Materials Research and Technology. DOI:10.1016/j.jmrt.2026.01.246, https://doi.org/10.1016/j.jmrt.2026.01.246
10. Yang, Y. F., Hu, F., Xia, T., Li, R. H., Bai, J. Y., Zhu, J. Q., & Zhang, G. F. (2025). High entropy alloys: A review of preparation techniques, properties and industry applications. Journal of Alloys and Compounds. DOI:10.1016/j.jallcom.2024.177691, https://doi.org/10.1016/j.jallcom.2024.177691

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