Melting, sintering and wetting properties of ZnO–Bi_2O_3–B_2O_3 sealing glass

Glasses based on ZnO-Bi_2O_3-B_2O_3 system are expected to be a new kind of sealing glasses because of their low melting temperature and other properties.In order to reveal the effect of B_2O_3 on the rheological behavior of ZnO-Bi_2O_3-B_2O_3 system glass melt,the properties of viscosity,thermal expansion,fluxion property and wetting process between cylinder samples and stainless steel were investigated with the rotating crucible viscometer,dilato meter and high-temperature microscope.The structure of sintered glass samples was investigated with scanning electron microscope.The results show that the B_2O_3 content increasing in B_1-B_3 at the given temperature between 400 ℃ and 500 ℃ leads to the increasing of the sample viscosity.When the amount of B_2O_3 increases from 5.24%to 9.24%(mass fraction),the coefficients of thermal expansion of glass samples decrease smoothly from 10.94×10^(-6) to10.71×10^(-6) and 10.38×10^(-6) ℃^(-1) respectively.In the case of sealing temperature,its value increases from 453 ℃ to 494 ℃.ZnO-Bi_2O_3-B_2O_3 system low-melting glass powder sintering was with viscous liquid to participate,which could make the densification of glass sample more effective and more efficient.With the content of B_2O_3 increasing,the wetting angle between the glasses samples and stainless steel could also increase,and the resulting appropriate sealing temperature range is 460-490 ℃.

Advances in Investigation of Fe-based Glass-forming Alloy Melts

Continuous precision casting is an important trend in modern industrialization.Clustering effects in glassforming metallic liquids tremendously influence the properties of rapidly quenched ribbons;therefore,much attention has been paid to the study of Fe-based glass-forming melts at high temperatures.Recent investigations of these melts are categorized and reviewed.It is concluded that more efforts are still required to reveal the discipline of amorphization brought about by rapid quenching of Fe-based glass-forming melts.

Fluidity, Microstructure, and Tensile Properties of Sub-rapidly Solidified Mg-6Al-4Zn-xSn(x=0,0.6,1.2,1.8) Alloy

In this paper, the infl uence of the Sn element on the melt viscosity, grain size, shrinkage, and tensile properties of the subrapidly solidified Mg-6Al-4Zn alloy was studied. The results showed that the melt viscosity of the Mg-6Al-4Zn alloy was greatly decreased because of the addition of Sn. As the content of Sn increased from 0 to 1.8 wt.%, the grain size of the alloy was refined, and the dendrite microstructure was changed to rose-shaped ones simultaneously. The decreased melt viscosity and refined microstructure were conductive to the feeding of melt, which contributed to the reduction in volume fraction of shrinkage. The volume fraction of shrinkage of the Mg-6Al-4Zn-1.2 Sn alloy was reduced by 30.8%, compared with that of the alloy without Sn addition. Tensile properties of the Mg-6Al-4Zn-x Sn alloys were increased firstly and then decreased with the augmented Sn content. The yield strength, ultimate tensile strength, and elongation of the alloy containing 1.2 wt.% Sn were 21.4%, 39.5%, and 259.0% higher than those of the alloy without Sn addition, respectively. The addition of Sn was considered to reduce the shrinkage of the sub-rapidly solidified Mg-6Al-4Zn magnesium alloy and thus improved its tensile properties. To identify the mechanism, the effect of Sn on the volume fraction of shrinkage was discussed from three aspects of melt viscosity, grain refinement, and volume fraction of eutectic phases.