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The effect of Cd and Sb addition on the microstructural and mechanical properties of as-cast AZ31 alloys was investigated and compared. The results indicate that the difference of Sb and Cd in the microstructure and mechanical properties of as-cast AZ31 magnesium alloy is significant. Addition of 0.15%Sb (mass fraction) to AZ31 alloy can refine the matrix and β-Mg17Al12phase but not form a new phase Mg3Sb2. Oppositely, by addition of 0.3-0.7% Cd to AZ31 alloy, Cd was dissolved into the AZ31 alloy, the phase composition did not change but was refined also. Accordingly, the Cd-refined AZ31 alloy exhibits higher tensile and impact toughness and Brinell hardness properties than the Sb- refined one. The difference of Sb and Cd in the mechanical properties is possibly related to the solid solution of Cd into the matrix and formation of Mg3Sb2which has the same close-packed hexagonal structure as α-Mg.

The number of steel-frame buildings is increasing as a result of development of social economy. However, the fire-resistant property of steel-frame buildings is much weaker than that of brick-frame buildings and RC-frame buildings. In response to such demand, fire-resistant steel has been developed since the last two decades. Mo is one of the most effective strengthening elements for the high-temperature strength of steels. With the increase of the Mo content in steels, there is a dramatic increase in costs which is unacceptable for the cost-sensitive construction area. Therefore, a fire-resistant steel with a low Mo content is highly desired. Two fire-resistant steels with low Mo content (

Changes in the primary Si phase in Al-Si alloys were analyzed and compared to the Si phase in ZA27 alloys with the same Si/Al ratio. The Si phase in the Al-Si alloys was modified and applied to ZA27 alloys to refine the Si phase of the microstructure. The results showed that the change in the ZA27 alloys was the same as that in the Al-Si alloys while good modification effects were obtained with a 1.5% Cu-P inter-alloy using two different processes.

The effect of Cd on the microstructure and mechanical properties of AZ31 magnesium alloy has been investigated in this paper. The results indicate that the microstructure of the AZ31 magnesium alloy is refined obviously by adding a little Cd. When 0.7%Cd is added, the alloy is made up of Al-rich α-Mg matrix and the phase of β-Mg17Al12 which distributes and disperses in the matrix uniformly. Cd solid dissolves in the matrix and there is no new phase formed, which contributes to the increase of the impact toughness, Brinell hardness, tension strength and elongation of the experimental alloy by 68.6%,10.3%,9% and 35%,respectively.

Two sintered magnets Nd15Dy1.2Fe77Al0.8B6 and Nd22Fe71B7 were modified by intergranular additions of Si3N4. The remanence as well as sintering density of the two magnets increased slightly with appropriate amount of Si3N4 additives. Meanwhile, there was an obvious increase in coercivity of the Nd-rich Nd22Fe71B7 magnet after 0.3 wt. % Si3N4 was added to magnets. Besides the effects on magnetic properties, an improved corrosion resistance was observed. Compared with the native magnets without any additions, corrosion potential of the magnets with Si3N4 additives is more positive and the current density in the anodic branch of the polarization curve is reduced. Microstructure observation reveals that Si3N4 additives have been incorporated into the intergranular phases in the magnets. Si is found to enrich in the Nd-rich intergranular phase with low oxygen content. With the introduction of Si3N4 additives, more intergranular phase with high oxygen content is formed, which may contribute to improved corrosion resistance. In addition, addition of Si3N4 refines the grain size of Nd22Fe71B7.

Full-potential linearized augmented plane-wave (FP-LAPW) method within the local density approximation plus self-interaction correction (LDA+USIC) has been applied to study the structure stability and electronic structure of ReSi1.75 and its doped systems with Al and Mo. Structural relaxation results show that the vacancy prefers to occupy the Si3 and Si4 site in the lattice with little ordering. For doping systems, Al prefers to substitute for Si at the Si3 site and Mo prefers to substitute for Re at the Re1 site. ReSi1.75 shows narrow gap semiconductor behavior with an indirect gap of 0.12 eV and a direct gap of 0.36 eV. Al doping compound remains semiconductor while Mo doping compound has a tendency to change into semimetals or metals. The Fermi level of doped systems moves into the valence band resulting in an increase of density of state at the Fermi level. It will enhance the thermoelectric properties and agrees well with the experiment results.