Comparative Evaluation of the TRIP Effect in Steels with Different Contents of Mn and Al

Abstract

This paper presents a comparison between four TRIP steels, which belong to two groups with different chemical compositions. The first group is that of steels with a relatively low contents of Mn (1.5–2%), high Al (1–2%) and about 0.2% C, and the second includes steels with lower percentages of C (0.1%) and Al (max. 0.6%), but with high percentages of Mn (over 5%). The steels were heat treated by incomplete austenitization, isothermally cooled in salt baths at 400 °C, followed by air cooling. The heat-treated samples were subjected to the impact bending test. A comparative study was performed from the point of view of the intensity of the TRIP effect, the development of the retained austenite-to-martensite transformation under shock (studied by SEM), X-ray analysis and hardness measurements. It was found that appropriate and similar behaviors in terms of mechanical shock were shown by two steels belonging to different groups, with similar amounts of the retained austenite being turned into martensite fractions. The steel with the highest Mn percentage was distinguished by having the highest hardness (362 HV) and the highest retained austenite (obtained after heat treatment) and martensite fractions (caused by the TRIP effect) (10.63% and 2.17%, respectively).

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“…Transformation-induced plasticity steels are first-generation steels with a fine-grained structure, which are characterised by high strength and high plasticity [91]. TRIP steels are defined as steels with increased ductility due to the phase transformation of retained austenite into martensite during the forming process [92,93]. The properties of TRIP steel are constituted by many strengthening mechanisms: solution, dispersion, work hardening, and phase transformation.…”

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“…Manganese additions will influence the hardness and strength of the steel and lower the temperature where austenite starts to decompose. The literature also shows Mn to reduce the critical cooling rate during hardening, increasing hardenability [129], [130]. When silicon additions increase for 3827 and 3832 from 0.1-0.5 Wt.%, the Ar 3 temperature increases by approximately 15°C.…”