SYNTHESIS AND CHARACTERIZATION OF LOW DENSITY STEEL

Abstract

Steel is an ever green structural material; but, it has a problem of low strength to specific weight ratio. This makes the use of steel in automobile industry slightly a less competitive, due to heavy weight and hence more energy consumption, leading to environmental pollution. In order to reduce density of steels, Al-addition by and large has drawn a large interest. However, it affects the mechanical properties of steel because of formation of hard and brittle intermetallic, namely k carbide. The thermodynamics of Mn addition may be an alternative proposal in the present work, as Fe-Al-Mn-C has the potential to provide exciting mechanical behavior. Melting or Sintering can be used as synthesizing technique for low density steel. Melting causes grain growth, dendritic microstructure and finally segregation of Mn as the allying addition. Thus an alternative route is testified here i.e. non-equilibrium synthesis of low density Fe-C-Mn-Al alloy, aiming for an exotic microstructure. With the advancement of modern technique like spark plasma sintering (SPS), the synthesis of bulk material from the mechanically alloyed powder may be a reality. In to execute this, elemental Fe, C, Mn and Al in desired quantiles were ball milled up to 40 h to ensure the formation of homogeneous solid solution. Thereafter consolidation of fine particle in SPS required optimization of the process parameters through trial and error, as an extensive part of the present research work, recording a temperature of 1000°C, pressure of 60 MPa and 50°C/min heating rate good enough to provide a density of 98.7% by Archimedes principle. Characterization by X-Ray diffraction, optical and scanning electron microscopy were performed to evaluate the microstructure formation, apart from determining equilibrium phase diagram by Thermo-Calc software. The bottom line provides a hardness of 920VHN for SPS sample, as compared to 560VHN for vacuum arc melted sample. The compression test in engineering stress-strain plot provided UTS of 1709 MPa while maintaining an extraordinary high elongation.