2090 – 12 – Tempering Martensite

Martensite is quite hard but brittle, so it needs to be tempered to get better ductility and alleviate the stress induced during quenching. Martensite is the only metal that needs to be tempered, a process during which manufacturers soak the metal at the lowest temperature, ensuring that it does not return to its austenite phase.
Tempering transforms some of the carbon trapped in the distorted crystal structure into cementite. While martensite loses some strength and hardness when tempered, it has much better ductility and toughness.