EFFECTS OF ANNEALING AND CASE HARDENING TREATMENT ON CAST ALUMINIUM AND ALLOY STEEL: A REVIEW

This review examines how annealing and case hardening affect the mechanical, microstructural, and physical-chemical behaviour of two widely used engineering materials: cast aluminium and alloy steel. Heat treatment remains one of the principal tools by which engineers tailor the in-service performance of metallic components, and the two materials respond to thermal processing in markedly different ways because of differences in crystal structure and alloy chemistry. Across the literature surveyed, annealing consistently lowers hardness and tensile strength while improving ductility, machinability, and dimensional stability in both materials, whereas case hardening, achieved chiefly through carburizing and nitriding, sharply raises the surface hardness and wear resistance of alloy steel while the core remains tough; cast aluminium cannot be case hardened in this sense because it does not form hard carbide or nitride layers and instead relies on alternatives such as anodizing or plasma electrolytic oxidation. Hence, practically selections of material should follow the governing engineering requirement; alloy steel where surface hardness, wear resistance, and load-bearing capacity dominate, and cast aluminium where weight saving and corrosion resistance take priority