**4. Evolution of high-alloy steel**

Alloy steel is added with a choice of elements in total amounts between 10 and 50 wt% to expand its mechanical properties. Alloyed steels are categorized into two groups: low- and high-alloy steels. The simplest form of steel is iron with carbon alloy (~0.1–1%). Common alloying elements comprise manganese (the most frequent one), chromium, nickel, molybdenum, silicon, aluminum, vanadium, titanium, niobium, and boron (B). Alloyed steels have improved properties such as strength, hardenability, toughness, hardness, wear resistance, corrosion resistance, and hot hardness [8]. To achieve these better-quality properties, the metal may require various heat treatment processes. Several of these are utilized in highly requiring applications, like in the turbine blades used in jet engines, in nuclear reactor, in spacecraft, etc. Iron, owing to its ferromagnetic nature, discovers major applications wherever the response to magnetism is important, like in transformers and electric motors.
