ANS:A - A fine, highly dislocated and strong martensite.

Maraging steels derive their strength primarily from a fine, highly dislocated, and strong martensitic microstructure. Therefore, the correct mechanism is: A fine, highly dislocated and strong martensite. Maraging steels are unique in that they undergo a special aging process after solution treatment (austenitizing) and quenching. During this aging process, the martensitic structure of the steel is strengthened by the precipitation of intermetallic compounds, typically containing elements such as nickel, cobalt, titanium, and molybdenum. While these precipitates contribute to the strength of maraging steels, it's the fine martensitic structure with high dislocation density that primarily provides their exceptional strength and toughness.