Analysis of the precipitation behaviour in a high-speed steel by means of small-angle neutron scattering

Small-angle neutron scattering (SANS) and energy-filtered transmission electron microscopy (EFTEM) were employed to characterise the precipitation behaviour in the high-speed steel HS6-5-2 during tempering. With SANS the evolution of the size distribution of precipitates during isothermal tempering at 590 °C was investigated. The SANS results are discussed assuming that three populations of precipitates can be distinguished during tempering at 590 °C. The smallest population with sizes around 1 nm is supposed to be carbon-rich clusters. Intermediate-sized particles between approximately 1 and 10 nm might be either MC and/or M2C carbides, which cannot be distinguished by SANS. In addition, the ratio A of magnetic and nuclear scattering intensity was used to gain information on the composition of the precipitates. The A-ratio is discussed assuming a substitution of iron in the precipitates by carbide forming elements with increasing tempering time. Finally, the correlation of the results obtained by SANS with those achieved by EFTEM is presented.