Dislocation-locking by carbon, nitrogen and boron in α-iron

It is shown experimentally that nitrogen-looking is appreciably stronger than carbon-locking. This is contrary to the customary assumption and it is suggested that there may be chemical as well as elastic interaction with the dislocations. Boron is found to produce even stronger looking than nitrogen. These variations in the locking strength alter the duetile-brittle transition temperature. The stronger the locking, the higher the transition temperature.