How did molybdenum make nickel-chromium armour steel less brittle?

When alloying steel, the addition of molybdenum improves the material's properties by promoting hardenability and toughness. In the context of nickel-chromium armour steel, molybdenum helps reduce brittleness by allowing for tempering at higher temperatures, which generates better ductility while maintaining the desired levels of hardness and strength.12

Furthermore, alloying elements like molybdenum influence the heat-treating process by slowing the diffusion of atoms through iron lattices, which delays allotropic transformations. This allows for deeper hardening of the workpiece with less internal stress compared to rapid quenching methods. By modifying these transformation conditions, molybdenum helps create a more uniform and resilient microstructure, effectively mitigating the brittleness that can otherwise occur in high-strength steel alloys.21