Study On Prepartion And Properties Of Sn-Bi Thermal Fuse

This paper will innovate the prepartion of Sn-Bi alloy,adopt the forming process to prepare excellent properties of Sn-Bi alloy for the first time.The studies of this paper are as follows:self-designed and developed a semi-solid mechanical mixing equipment,used semisolid forming process to prepare Sn-Bi alloy,the prepartion of the Sn-Bi thermal fuse through the extrusion technology.The microstructure and mechnical properties of Sn-52Bi alloy and Sn-58Bi alloy which produced by the semisolid process were investigated by DSC,tensile strength test,OM and wettability test.In addition,study the ambient temperature on the impact of Sn-Bi thermal fuse properties.These researches indicate: The semisolid metal device is used the theory of shear stress to produced semi-solid slurry.Test results proved that the equipment can be prepared by small solid particles and uniformity semisolid Sn-Bi alloy slurry.For Sn-52Bi hypoeutectic alloy, Analysis of test results showed that optimal microstructure of semisolid Sn-52Bi alloy had been obtained under conditions that at shear time 10min with fixed agitating rate 320r /min, for the temperature of 145℃or so, and obtained the smaller and nearly rounded solid particles. The tensile strength and elongation of the Sn-Bi alloy which produced by semisolid processing compared to general extrusion casting were increased by 23% and 28% respectively, the elasticity coefficient is also increase. The wettability of semisolid Sn-52Bi alloy was fit for thermal fuse basic requirements.For Sn-58Bi eutectic alloy, alloy microstructure had improved after semisolid stirring, dendrite has a different degree of fragmentation and grain size has decreased. Also got nearly spherical grain, but not nearly equiaxed of solid particles. The tensile strength and elongation of the Sn-58Bi alloy which produced by semisolid processing compared to general extrusion casting were increased, but not showing a certain degree of regularity. The wettability of semisolid Sn-58Bi alloy was fit for thermal fuse basic requirements.Thermal fuse placed under 10 days in the ambient temperature of -10℃, test results showed that the microstructure of samples with no apparent change, the tensile strength and elongation of thermal fuse have a certain decreased. Thermal fuse placed under 10 days in the ambient temperature of 10℃, test results showed that the microstructure and mechanical properties of samples with no apparent change . Thermal fuse placed under 10 days in the ambient temperature of -10℃and 10℃, the wettability of semisolid Sn-Bi alloy was fit for thermal fuse basic requirements.