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Understanding the nature of the magnetic-field-induced precipitation behaviors represents a major step forward towards unravelling the real nature of interesting phenomena in Fe-based alloys and especially towards solving the key materials problem for the development of fusion energy. Experimental results indicate that the applied high magnetic field effectively promotes the precipitation of M 23 C 6 carbides. We build an integrated method, which breaks through the limitations of zero temperature and zero external field, to concentrate on the dependence of the stability induced by the magnetic effect, excluding the thermal effect. We investigate the intimate relationship between the external field and the origins of various magnetics structural characteristics, which are derived from the interactions among the various Wyckoff sites of iron atoms, antiparallel spin of chromium and Fe-C bond distances. The high-magnetic-field-induced exchange coupling increases with the strength of the external field, which then causes an increase in the parallel magnetic moment. The stability of the alloy carbide M 23 C 6 is more dependent on external field effects than thermal effects, whereas that of M 2 C, M 3 C and M 7 C 3 is mainly determined by thermal effects.

During continuous heating of a low-carbon low-alloy steel in a dilatometer, an abnormal macroscopic expansion has been observed in the length change of the sample during the onset of austenite formation. Such abnormal expansion behavior is also detected in the literature data with similar initial microstructures and heating rates on various steels. Here, this work investigates the causes and consequences of this abnormal expansion using in situ high-energy X-ray diffraction analysis. According to the volume investigated by diffraction, a significant amount of austenite forms before the onset of the macroscopic contraction of the sample associated with the bainite-to-austenite transformation. The delay in the macroscopic contraction is due to the retained austenite lattice expansion, arising from the concentration inhomogeneities in this phase produced by carbides dissolution during austenitization. The retained austenite lattice expansion manifests as a macroscopic expansion in the length change of the sample. Such abnormal expansion results in a significant overestimation of the Ac1 temperature, and a systematic shift in the austenite formation kinetics determined by dilatometry in comparison with X-ray diffraction. [ABSTRACT FROM AUTHOR]

The effects of a high magnetic field on proeutectoid ferrite nucleation kinetics has been investigated. SEM equipped with Electron backscattering diffraction are utilized to distinguish the quantity and morphology of proeutectoid ferrite. Results indicate that proeutectoid ferrite nucleation density approximately increased about 11–17% from 1033 to 993 K. Magnetization energy induced by high magnetic field is responsible for ferrite nucleation density increasing. According to Weiss molecular field theory, relationship between magnetic flux density, temperature and nucleation rate of proeutectoid ferrite is clarified. Nucleation kinetics model of proeutectoid ferrite under high magnetic fields is proposed. [ABSTRACT FROM AUTHOR]

Powder bed 3D printing is an additive manufacturing process that combines powder particles by selectively depositing a liquid activator on a powder bed. Sand molds for high-resolution casting can be realized as a high-quality green body via powder bed 3D printing. In this study, we investigated the effect of vertical penetration of aqueous droplets on the quality of the green body formed from a cement-mixed sand powder. The cement was hydrated by aqueous droplets and acted as a binder between the sand particles. The penetration ratio of the prepared powders was calculated from the penetration depth and spread diameter. Evidently, the penetration ratio and penetration resolution determined the strength and surface resolution of the green body. The results showed that an increase in the silica sand grain size led to a desirable penetration resolution with a relatively high green body strength at the same cement content. Additionally, the green body made from the sand with a particle size of 70 μm showed a relatively high green body strength and an excellent green body surface resolution even at 5% cement content, and it was determined that the green body strength and resolution depend on the penetration pattern. [ABSTRACT FROM AUTHOR]

Two alloys containing different Mg contents have been used to study the combined effect of stirring and oxidation on microstructure and ductility. The results show that intensive stirring can sufficiently disperse the α-Al particles and enable better liquid feeding during solidification and consequently reduce the porosity. The morphology of the oxides is determined by the amount of both Mg and stirring. With lower Mg content, the oxides present as oxide films, which can be broken up during stirring. In alloy with higher Mg content, the oxides exist as particles with numerous cracks, and the particle size increases slightly after stirring. In the Magsimal 59 alloy, due to the presence of large clusters of pores in the fracture surface, the influence of the small oxide particles on the ductility is negligible. In contrast, in the 42000 alloy, large oxide films on the fracture surface are correlated with the ductility. [ABSTRACT FROM AUTHOR]