Abstract
The effect of in-situ precipitating particles on the grain size of Al-Ti-treated and untreated Hadfield steel cast in a pilot scale environment was studied. Hadfield steel was melted in an induction furnace and cast in Y-Block samples. Light Optical Microscopy (LOM) and the intercept method were utilized for the grain size measurements. Additionally, Thermo-Calc Software TCFE7 Steels/Fe-alloys database version 7 was used for thermodynamic equilibrium calculations of the mole fraction of particles. The planar disregistry values between the austenite and the precipitating particles were calculated. It was observed that increasing oxide content in samples with low Ti(CN) content resulted in a finer microstructure, while increasing the Ti(CN) content under similar oxide content levels led to a coarser microstructure. The potency of each type of particle to nucleate austenitic grains was determined. Spinel (MnAl2O4, MgAl2O4) particles were characterized as the most potent, followed by olivine (Mn2SiO4), corundum (Al2O3, TiO2), and finally Ti(CN), the least potent particle.
Highlights
It is well established within the scientific community that refining the microstructure of a metallic material most often results in a significant improvement of the mechanical properties of the material, such as yield strength, toughness, hardness, and wear resistance
Alongside traditional methods such as casting temperature and controlling the cooling rate of the casting, techniques such as inoculation and precise composition selection are widely accepted among researchers as effective ways of controlling grain growth in metallic materials during solidification
It has been proven that in δ-iron, amongst other materials, the choice of a potent inoculant can be based on the disregistry, a value that shows the degree of the crystallographic mismatch between an inoculant substrate and the matrix phase [2]
Summary
It is well established within the scientific community that refining the microstructure of a metallic material most often results in a significant improvement of the mechanical properties of the material, such as yield strength, toughness, hardness, and wear resistance.Alongside traditional methods such as casting temperature and controlling the cooling rate of the casting, techniques such as inoculation and precise composition selection are widely accepted among researchers as effective ways of controlling grain growth in metallic materials during solidification.Inoculation is a practice where particles or alloying elements are added into the melt with the aim of modifying a forming phase to a finer microstructure or of providing an adequate number of nucleation sites for grains to nucleate and grow [1].It has been proven that in δ-iron, amongst other materials, the choice of a potent inoculant can be based on the disregistry, a value that shows the degree of the crystallographic mismatch between an inoculant substrate and the matrix phase [2]. It is well established within the scientific community that refining the microstructure of a metallic material most often results in a significant improvement of the mechanical properties of the material, such as yield strength, toughness, hardness, and wear resistance. Alongside traditional methods such as casting temperature and controlling the cooling rate of the casting, techniques such as inoculation and precise composition selection are widely accepted among researchers as effective ways of controlling grain growth in metallic materials during solidification. Bramfitt [2] calculated the disregistry of several nitrides and carbides by formulating Equation (1) [2] and showed that particles with lower disregistry are more potent substrates for nucleating δ-iron.
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