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Solidification parameters, microstructures, and mechanical properties of rapidly solidified iron‐based alloys
Author(s) -
Frommeyer Georg,
Vogt Erhard
Publication year - 1987
Publication title -
steel research
Language(s) - English
Resource type - Journals
eISSN - 1869-344X
pISSN - 0177-4832
DOI - 10.1002/srin.198700254
Subject(s) - materials science , microstructure , cementite , eutectic system , metallurgy , alloy , ultimate tensile strength , equiaxed crystals , ribbon , composite material , austenite
Cooling rate measurements were carried out using a computer controlled melt spinning unit for the production of rapidly solidified Fe 6.3 wt.% Si and Fe 3.2 wt.% C melt spun ribbons employing a wide range of process parameters. The cooling rates are mainly a function of the ribbon thickness, and are independent of the alloy composition and wheel material. The resulting microstructures have been characterized by light optical and electron microscopy (SEM and TEM) investigations and were found to be influenced by the cooling conditions during and after solidification. Grain sizes and secondary dendrite arm spacings are related to the cooling rates by means of exponential relationships. In addition to this, rapidly solidified eutectic Fe 4.2 wt. %C alloy powder was produced by argon melt‐atomization. Powder particles of 20 μm to 80 μm size solidified microcrystalline and exhibit cementite, metastable γ‐phase, and martensite. The cementite matrix is of dendritic structure. After consolidating the powder by hot pressing below A, the microstructure changes to the fine equiaxed grains containing about 66 Vol.% Fe 3 C and a dispersoid of ferrite ≤1 μm within the cementite matrix. This material exhibits high tensile strength and wear resistance at room temperature. At elevated temperatures in the region between 650°C and 750°C, and at strain rates of ε ⋍ 10 −4 s −1 the fine grained ceramic‐like material reveals superplastic behaviour.