Papers by Keyword: ε Martensite

Abstract: It has been shown that the conversion of austenitic manganese steels – via their purposeful alloying – into the class of precipitation-hardening materials (when aging leads to the formation of VC carbides) provides for high values (2.5-2.7 %) of the shape memory effect (SME) and considerable improvement in strength characteristics of the steels after aging and implementation of γ→ε→γ transformations. Strength characteristics and SME can be governed in wide limits by means of controlled changing of the amount, dispersity, and distribution of VC carbides during aging. The shape memory effect with a reversible deformation of 1.6—1.7% in the metastable steels such as 0.20C-20Mn-2Si-1V with an ε–martensite initial structure is obtained as a result of the retwinning of ε martensite during cold deformation and the subsequent ε→γ transformation during heating.

Abstract: The ε martensite phase was investigated in three types of FeMn (Cr) steels by means of metallographic, EBSD and XRD methods as well as by dilatometric and DSC examinations during heating and cooling. In the course of the latter examinations, the transformation temperatures (Ms, A_s) of ε martensite were determined in the previously deformed samples as well. The results were also compared to the thermodynamic data published in the references describing the γε and γα transformations.

Abstract: Microstructures and damping properties have been investigated in Fe-23%Mn-(0~2)%Si and Fe-23%Mn-(0~2)%Co alloys, based on experimental results from metallography, X-ray diffractometry and vibration test in a flexural mode. The amount and number density of ε martensite are increased with an increase in Co content, resulting in the improvement of damping capacity. For the same ε martensite content, the higher the Co content, the greater the damping capacity. On the contrary, an addition of Si affects to decrease the amount and number density of ε martensite, giving rise to a decay of damping capacity. The decreased ε martensite content by the addition of Si would be attributed to an increase in critical driving force for the γ→ε martensitic transformation by solution hardening effect.