TRIP (transformation induced plasticity) steel are modern structural materials which are currently mainly used in an automotive industry. The processing of these steels utilize an effect of transformation induced plasticity resulting in good mechanical properties – high strength (up to 1200 MPa) and formability (around 35 %). TRIP effect is based on stabilisation of sufficient amount of retained austenite and its transformation into strain induced martensite in consequence of applied plastic deformation at low temperature. The properties of this steel are based on a multiphase microstructure, which consists of ferrite, bainite and retained austenite. In this work, CMnSiAl steel was heat treated using various processing parameters. Three different temperature of austenitization (850 – 900 – 950 °C) were applied and the samples were subsequently cooled by cooling rates in the range of 26 – 32 °C / s to different bainitic hold temperatures ranging 410 – 460 °C. The resulting microstructures were evaluated with use of optical and scanning electron microscopy and volume fraction of retained austenite was determined using X-ray diffraction phase analysis. Mechanical properties of this steel were established by HV10 hardness measurement, which reached the values 260 – 301 HV10.Keywords: TRIP steel, partial substitution, retained austenite
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