Papers by Keyword: Sn-Bi Alloy

Abstract: The directional solidification process of Sn–10 wt% Bi alloy with low melting point was observed by synchrotron X-ray imaging technology. The mold temperature was controlled, and the dynamic images of a series of alloy solidification behavior were obtained. The results show that columnar crystal grows in dendrite morphology. It is also found that dendrite morphology changes at different mold temperature. With the decrease of the mold temperature, the dendrite morphology begins to change from irregular to regular, and finally, the primary dendrites and the secondary dendrites are perpendicular to each other.

Abstract: Lead-free solders have been gaining more and more attention recently. Sn-Bi system is one of the most promising candidates as the lead-free solder materials. In this article Polyoxyethylene lauryl ether (Brij 35) was used as the additive in the electrochemical deposition of Sn-Bi alloy. Various current densities and bath compositions have been investigated. Sn-Bi composites were successfully deposited on a copper substrate. The deposits were then characterized and studied by scanning electron microscopic (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and differential scanning calorimeter (DSC). Results indicate that the morphology and crystalline orientations are composition dependent. Intermetallic compound (IMC) was formed during the reflow process.

Abstract: To manufacture rapid metal tools, an innovative method based on rapid prototyping and high pressure spraying technologies is proposed in this study. The Sn-Bi metal alloy with low melting point and small thermal shrink was used as the spraying materials. Applying an electric heated device and high pressure boost pump, the melting Sn-Bi Alloy went through a small spray nozzle and atomized into semi-melting minute particles. The atomized particles are then deposited and integrated on the surface of intermediate silicone rubber mold, which is made from the rapid prototyping (RP) system and are successfully used to manufacture rapid wax injection mould. Using the thermal spraying system to manufacture rapid metal mold, the surface quality and the dimensional accuracy of the spray mold is excellent and the fabricated cycle time is short.

Abstract: In this paper, a new kind of Sn-Bi lead-free solder was fabricated via rapid solidification method by adding a series of microelements which can optimize the properties of Sn-Bi solder. When the solder was manufactured by Single Roller Melt Spinning Process, the faster the cooling rate is, the better the effect of restraining Bi segregation is. When the melt spinning rate was up to 1000 rpm, it had the best result. The effects of microelements on the melting characteristics, microstructure and properties of the new solder were also systemically studied. The results show that when the added content of Ag is 0.7%, Cu 0.3%, Ge 0.1%, In 0.5% and Sb 0.5%, the microstructure of the solder is fine, the extent of Bi segregation obviously decreases and the mechanical property is similar to that of Sn-37Pb solder. The melting point of the new solder is close to that of the Sn-37Pb solder. The mechanical and soldering properties are also similar to that of it.

Abstract: In this paper, the technology of semi-solid casting was to used are produced Sn-Bi alloy. The influence of agitating time at 125 °C on the microstructure and mechanical properties of of Sn-58Bi casting alloy were discussed. The eutectic Sn-Bi alloy was mechanically agitated during the casting solidification process. The results indicated that non-lamellar Sn-Bi structure with long plate shape, short strip, small size block and suborbicular block shape Sn phase was obtained for different stirring time. The elongation of Sn-Bi alloy with non-lamellar eutectic structure is improved prominently. Compared with the elongation of lamellar eutectic Sn-Bi alloy prepared by conventional die casting, the elongation of semi-solid Sn-Bi alloy with suborbicular block shape Sn phase is enhanced up to 45%.

Abstract: Preparation of semi-solid Sn–58Bi alloys by mechanical stirring casting method was investigated. The effect of temperature below the melting temperature on the microstructures and mechanical properties of semi-solid Sn–58Bi alloys was discussed. The experimental results showed that long plate shape, block shape and suborbicular Sn phases were formed by mechanical agitation during the casting solidification process. The non-lamellar Sn-Bi Microstructure improves prominently the elongation of Sn-Bi alloy. The elongation of semi-solid Sn-Bi alloy with suborbicular Sn phase is enhanced up to 37% compared with the elongation of lamellar eutectic Sn-Bi alloy prepared by conventional die casting. After the agigation above 130 °C, non-lamellar Sn-Bi eutectic structure is formed and lamellar Sn-Bi eutectic precipitates. When the agitating temperature was 135 °C, the elongation of semi-solid Sn-Bi alloy mixed with non-lamellar and lamellar Sn-Bi alloy microstructure is enhanced up to 24%.

Abstract: External fields (e.g. electromagnetic field, electric field, etc.) are often applied to modify the solidification structure of metallic alloys. The dynamic process of structure modification is invisible because of the opacity of metallic alloys. To understand the modification mechanism, it is necessary to discover the microstructure evolution during solidification. In present paper, we focus on studying the influence of pulsed electric current (PEC) on dendrite growth of Sn-Bi alloy by insitu and real time observation using the third synchrotron X-ray source at Shanghai Synchrotron Radiation Facility (SSRF) in China. The modification mechanism of PEC on solidification structure is analyzed based on a series of real time observations.

Abstract: In this work, the effect of stirring time on the solidifed microstructures and mechanical properties of semi-solid Sn-Bi slurry was investigated by the mechanical stirring method. The results indicated that a fine round granular solidifed structure of Sn-Bi semi-solid slurry was obtained at 142 and stirred for 8 min. Compared with the Sn-Bi alloy prepared conventional die casting, the mechamical properties of semi-solid Sn-Bi alloy was improved prominently. The percentage elongation of semi-solid Sn-Bi alloy was increased 67 % compared with that of the Sn-Bi alloy prepared conventional die casting.