Microstructural characterisation of intercritically annealed 0·5 wt-%Ni and Mn added steels prepared by powder metallurgy method

Abstract In the present study, atomised iron powder (Ancorsteel 1000) was mixed with 0·3% graphite, 0·3% graphite + 0·5%Ni and 0·3% graphite + 0·5%Mn. After sintering at 1120°C, specimens were intercritically annealed at different temperatures (724, 735 and 760°C) and water quenched. Through this heat treatment, it was intended to produce a ferrite + martensite (dual phase structure) microstructure in powder metallurgy processed steels. It was seen that all specimens were sensitive to the intercritical annealing (ICA) temperatures. While Ni rich martensite phase in ferrite matrix was produced in Ni added specimens, Ni concentration of martensite phase decreased with increasing ICA temperatures. Martensite phase with high porosity content in ferrite matrix was produced in Mn added specimens. It was observed that in all specimens, martensite volume fraction increased with increasing ICA temperature and the most effective alloying element on martensite volume fraction was found to be Mn.

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