Effect of Ni on solidification of duplex low density steels
Recently, low density Fe Mn Al C steels have attracted attention because of their low density with excellent combinations of strength and ductility. They can be divided into three categories: ferritic steels, duplex steels and austenitic steels, depending on the microstructure. The solidification of five duplex low density steels was investigated. Five steels Fe 15Mn 10Al 0.8C, Fe 15Mn 10Al 1.7Ni 0.8C, Fe 15Mn 10Al 3.9Ni 0.8C, Fe 15Mn 10Al 5.6Ni 0.8C and Fe 15Mn 10Al 8.6Ni 0.8C were produced in a vacuum induction furnace under Ar atmosphere and remelted in a simultaneous thermal analyser (NETZSCH STA 449 C Jupiter) The influence of Ni on the solidification process was analysed using thermodynamic calculations and differential scanning calorimetry. The samples were analysed by light microscopy. The thermodynamic modelling was performed with commercial software Thermo Calc using the CALPHAD method. The Thermo Calc calculations show a better agreement for the liquidus temperatures at lower Ni additions, while the higher Ni additions show a better agreement for the solidus temperatures. The Ni additions slightly increase the density, reduce the distance of the secondary dendrite arms and lower both the solidus and liquidus temperatures, but do not influence the solidification interval.
Journal of Thermal Analysis and Calorimetry