Thanks to fast in situ X-ray diffraction experiments and to the use of advanced methods for data analysis, the behavior of two steel grades has been investigated in details during heat treatment and especially during quenching. The level of knowledge about ongoing phenomena has been considerably improved. In particular, new results about martensite crystal structure, self-tempering effects, austenite stabilization, creation of 2nd kind hydrostatic residual stresses in martensite and austenite, evolution of dislocation density and phase specific density were generated. Based on the present results, new models can be developed and more reliable FEM heat treatment simulations can be achieved and help to enhance the knowledge on distortion as well as optimize heat treatment parameters.
