Semicoherent precipitates in a Fe-Cr-C alloy

Precipitation processes in ferromagnetic materials can be recorded very well by measuring the sensitive coercive field strength. It should be tested, whether also semicoherent precipitates have a sufficient clear interaction with Bloch-walls. For this purpose the mild-magnetic alloy X1FeCr25 served, To carry out the evidence sensitively, a method based on differences between H-C(t) (heat-treated state at T 600...700 degreesC) - H-C(0) (quenched state from high temperature) = Delta H-C was used. A quantitative record of the amount of precipitates (as particle size) is possible by a decomposition parameter Delta H-C/Delta t. Plate-like beta'-precipitates with planes {100}parallel to{100} in the alpha-Fe solid solution have been proved by transmission electron microscopic investigations; this is the preparation state for the transition into the stable fee phase M23C6. As a result, the quantitative electron microscopic proof of the beta'-phase can be supported by magnetic measurements, qualitatively and quantitatively. The estimated values of the activation energy for the process in the 1st maximum of precipitation in X1FeCr25 are higher than for the stable phases as the orthorhombic M3C or the cubic complex M6C in other steels and give a hint to the difficult processes related to nucleation as to the transition into M23C6.