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The effect of strain rate on strain-induced -martensite transformation and mechanical behavior of austenitic stainless steel grades EN 1.4318 (AISI 301LN) and EN 1.4301 (AISI 304) was studied at strain rates ranging between 3 ϫ 10 Ϫ4 and 200 s Ϫ1 . The most important effect of the strain rate was found to be the adiabatic heating that suppresses the strain-induced transformation. A correlation between the work-hardening rate and the rate of transformation was found. Therefore, the changes in the extent of the ␣Ј-martensite formation strongly affected the work-hardening rate and the ultimate tensile strength of the materials. Changes in the martensite formation and workhardening rate affected also the ductility of the studied steels. Furthermore, it was shown that the square root of the ␣Ј-martensite fraction is a linear function of flow stress. This indicates that the formation of ␣Ј-martensite affects the stress by influencing the dislocation density of the austenite phase. Olson-Cohen analysis of the martensite measurement results did not indicate any effect of strain rate on shear band formation, which was contrary to the transmission electron microscopy (TEM) examinations. The ␤ parameter decreased with increasing strain rate, which indicates a decrease in the chemical driving force of the transformation. g S a¿ g S a¿ g S a¿ g S a¿ g S a¿

Several techniques for measuring the strain induced a9-martensite content in EN 1.4318 (AISI 301LN) and EN 1.4301 (AISI 304) austenitic stainless steels were compared in order to determine a correlation curve between Ferritescope measurement results and actual a9-martensite contents. The studied methods involved Satmagan measurement, magnetic balance measurement, X-ray diffraction, density measurement and quantitative optical metallography. Satmagan, magnetic balance and density measurements were found to give equal a9-martensite contents. X-ray diffraction results were affected by the texture but averaging of several diffraction peaks improved the reliability of the results. It was shown that a9-martensite can be detected by means of optical metallography, but quantitative analysis is time consuming and inaccurate. The relationship between the Ferritescope results and actual a9-martensite contents measured with the other techniques was found to be linear. According to the results, the Ferritescope readings can be converted to actual a9-martensite contents by multiplying with a correction factor of 1 . 7.MST/6120

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