Effect of alloying additions on structure and mechanical properties of high carbon Fe-16 wt.% Al alloy

Effect of quaternary alloying elements Mn, Cr, Ni and Ti on structure and p roperties of Fe3Al-based alloy containing about 1 wt.% carbon have been inv estigated. Four different alloys were prepared. The composition of the quat ernary alloying element was proposed to be approximate to 4 wt.% and was su bstituted for iron. Processing of Fe-16Al-4.1Mn-1.0C, Fe-16.5Al-3.5Cr-0.94C , Fe-16Al-4.0Ni-0.9C and Fe-15.6Al-2.8Ti-1.0C alloys through a combination of air induction melting with flux cover (AIM) and electroslag remelting (E SR) yields a sound ingot free from macro and microporosity with very low su lphur, oxygen and nitrogen. This process route also exhibited excellent rec overy of alloying elements. As-cast alloys were examined using optical micr oscopy, X-ray diffraction, electron probe microanalyses (EPMA) and scanning electron microscopy (SEM) in conjunction with energy dispersive X-ray anal ysis to understand the microstructure of these alloys. The as-cast ESR ingo ts of alloys containing Mn, Cr and Ni exhibited a two-phase structure of Fe 3AlC0.5 precipitate in the Fe3Al-based matrix. Both phases exhibited consid erable amount of solid solubility for Mn, Cr and Ni, whereas the alloy cont aining Ti exhibited a three-phase microstructure of TiC particles and Fe3Al C precipitates in the Fe3Al-based matrix. This alloy has also exhibited ver y low solubility of Ti in the Fe3Al-based matrix and no solubility in the F e3AlC precipitates. Several microcracks were observed in the as-cast ESR in gots of the high carbon Fe3Al alloy containing Ni and tensile tests could n ot be carried out for this composition. Tensile and creep tests were perfor med on the high carbon Fe3Al alloys containing Mn, Cr and Ti in the as-cast condition. No improvement in room temperature tensile strength and inferio r high temperature strength and creep properties was observed by the additi on of quaternary alloying elements. (C) 2000 Elsevier Science S.A. All righ ts reserved.