Malleability Definition — MFDS Part 1 MCQ
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Correct answer: A — Ability to undergo permanent deformation under compressive stress without fracture
Malleability is the ability of a material to undergo permanent plastic deformation under compressive loading without fracturing, as when a metal is hammered or rolled into a thin sheet. Therefore, A is correct. Option E defines ductility: plastic deformation under tensile loading, classically demonstrated by drawing a metal into wire. Option B describes hardness, usually assessed by resistance to indentation. Option C describes fracture toughness, which concerns resistance to crack propagation. Option D describes elastic recovery: the material returns towards its original dimensions when the load is removed, whereas malleable deformation is permanent. Gold is a familiar dental example of a highly malleable metal.
Reference: Mondal A, Bhattacharya B, Das S, et al. Metal-like Ductility in Organic Plastic Crystals: Role of Molecular Shape and Dihydrogen Bonding Interactions in Aminoboranes. Angew Chem Int Ed Engl. 2020;59:10971–10980. https://pubmed.ncbi.nlm.nih.gov/32087039/