Research on the Microstructure and Microhardness of 9Cr18 Semi-Solid Billet

Formed in the semi-solid state, materials can obtain unconventional microstructures and properties compared with traditional method. In this paper, semi-solid billet of 9Cr18 steel was obtained through a wavelike sloping plate. Microstructure analysis of the semi-solid billet was conducted through scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). X-ray diffraction (XRD) test and microhardness test were also used to analyze the properties. The results showed that the structure of 9Cr18 semi-solid billet contained globular primary austenite and secondary austenite-Cr7C3 eutectic. Globular primary austenite grains were first formed during partial solidification in the sloping plate, and then the rest liquid metal formed secondary austenite and Cr7C3 eutectic structure surrounding the primary grains. Cr atoms had a concentration in the rest liquid side, which along with C atoms contributed to the formation of the Cr7C3 carbide. Hardness in the primary solid grain area and the eutectic area was about 330 HV and 650 HV, respectively. These specific properties were important for subsequent thixoforming of the functional graded materials.

A study of microstructure and ductility of directionally solidified Ni50Al20Fe30

The microstructure and ductility of directionally solidified Ni50Al20Fe30 were studied. Calculation and experiment show that the elastic modulus of the sample with completely eutectic lamellar structure is higher than that of the sample with dendritic structure. During deformation, in the samples with dendritic structure, some load is transferred from the proeutectic area to the γ-rich eutectic area and enhances the ductility of the sample.The existence of thick interdendritic γ phase and thick lamellar γ phase in the eutectic area of the dendritic sample is very effective in suppressing the microcrack propagation and also contributes to the ductility enhancement.