材料期刊网

在150℃下对半固态亚共晶 Sn-52Bi 浆料分别进行5,10和15 min 的机械搅拌,采用真空吸铸水冷制备出半固态Sn-Bi合金,测试了半固态Sn-Bi合金的组织、力学与热性能,研究剪切力对半固态浆料组织演变的影响,探索半固态合金延伸率与熔化潜热的关系.结果表明：对 Sn-52 Bi 半固态浆料进行机械搅拌,剪切力可抑制树枝状初生 Sn 相的形成,真空吸铸水冷得到的合金组织由非树枝状的初生 Sn 相和共晶体构成；随着搅拌时间的延长,短锤状初生 Sn 相转变为直径约20μm的近球状,搅拌时间延长至15 min时球状初生Sn相直径变小但出现团聚.当搅拌速度为320 r/min,机械搅拌时间为10 min 工艺得到半固态Sn-Bi合金延伸率为46．75％,与180℃下的合金熔液直接水冷凝固相比提高了160％；差式扫描量热分析(DSC)得出：不同机械搅拌时间半固态 Sn-52 Bi 合金的峰值温度为140℃,随着合金延伸率升高,合金的熔化潜热减小.

The hypo eutectic semi-solid Sn-52Bi slurry at 150 ℃ was mechanically agitated for 5,10 and 15 min, respectively,and cooled by water after vacuum suction casting.The microstructure,mechanical property and latent heat of semi-solid Sn-52Bi were tested.The effect of the shear force on the microstructure evolution of low solid fraction of Sn-52Bi semi-solid slurry and the correlation between elongation and latent heat of semi-solid alloys were investigated.The results show that during mechanical agitation of the semi-solid Sn-52Bi slur-ry,the shear force can inhibit the formation of dendritic primary Sn phase.The microstructure of semi-solid Sn-52Bi alloy consists of non-dendrite primary Sn and the eutectic.With the stirring time increase,primary Sn phase changes from short mallet particles to nearly spherical particles with the diameter of about 20μm.When the time of mechanical stir increase to 1 5 minutes,the diameter of spherical primary Sn phase becomes smaller, but the particles appear aggregation to some extent.The elongation of semi-solid Sn-52Bi alloy obtained by me-chanical stirring speed of 320 r/min for 10 min is 46.75%,which is improved distinctly by 129.10%,compared to conventional liquid casting Sn-52Bi alloy.The analysis of DSC curve shows the endothermic peak temperature of the semi-solid Sn-52Bi alloys prepared by different time of mechanical stir is 140 ℃.The higher the elonga-tion is,the smaller the latent heat is.