Martensitic Twinning
Martensitic twinning is a deformation mechanism in high-carbon steels where crystal regions orient mirror-symmetrically to the twin plane and relieve local transformation stresses.
Physical-Chemical Mechanism of Action
During martensitic transformation in high-carbon steels, high internal stresses develop. Martensitic twinning is a secondary plastic deformation mechanism where crystal regions orient mirror-like to the twin plane. This leads to a reduction of local transformation stresses.
Metallurgical Relevance & Welding Risks
Martensitic twinning can lead to a glass-hard, crack-sensitive structure if cooling is too fast (short t8/5 time). This increases susceptibility to hot cracking and reduces the mechanical properties of the weld.
Shop Practice & Action Items
To avoid martensitic twinning, control the cooling in the weld zone. A t8/5 time of 5 to 10 seconds is ideal for most high-carbon steels. Use a suitable cooling method or strategy to regulate the cooling rate and stabilize the structure.