Correlation between the Mechanical Properties and the Strain-Induced Martensite Content Found by Various Techniques in an Austenitic–Martensitic TRIP Sheet Steel

The strain-induced martensite content in an austenitic–martensitic VNS9-Sh TRIP sheet steel is estimated by magnetic and X-ray diffraction techniques, and the results are compared. The influence of the martensite content on the static tensile and hardness properties is studied. The difference in the strain-induced martensite contents determined by magnetic and X-ray diffraction techniques is shown to depend on the strength of the steel. This difference is maximal when the strength properties are low. There is a good correlation between the hardness and the strain-induced martensite content in the surface layers of the material. The considerable scatter in the experimental data obtained for different steel heats results from the difference in the chemical compositions and the peculiarities of strain-induced martensite formation.