本研究探討通電對純錫之微結構性質變化的機制。本研究對純錫薄帶施以電流密度5000~7500 A/cm²之直流電，觀察在不同的電流密度下材料機械性質及電性的改變、微結構變化，並嘗試計算純錫微結構及性質改變之活化能，以了解電流對材料影響的機制。通電之後以穿透式電子顯微鏡進行觀察，顯示晶格受到電子風力影響使得晶格結構扭曲且產生差排，試片內部差排密度上升，且利用電子背向散射衍射分析微結構，其結果顯示通電後晶粒尺寸及晶粒取向變化。通電後，細晶比例提高，且在電流密度5000~6500 A/cm²的條件下產生晶粒細化，推測是由於大量差排作為再結晶成核點，加上通電所伴隨之焦耳熱提供能量，引發再結晶現象的產生，進而生成許多細小的晶粒；在電流密度7000~7500 A/cm²的條件下產生晶粒成長，推測是由於高溫加速再結晶完成並使得晶粒開始成長。通電後，試片微硬度受到應變強化及晶界強化機制影響而上升；片電阻值則是受到晶粒取向變化影響而下降。

This study investigated the mechanism of the microstructure and properties variation of Sn under current stressing. The pure Sn strip specimens were subjected to current stressing under current density 5.5~7.5 kA/cm² for 0.5h, 2cycles. The specimens were rapidly quenched with liquid nitrogen after current stressing to freeze the microstructure for investigation. The mechanical and electrical properties of the pure Sn strips were investigated using Vickers micro-hardness tester and 4-point probe, respectively. The microstructure variation under different current stressing conditions was investigated using electron back scattered diffraction analysis(EBSD) and transmission electron microscope(TEM). The activation energy for the properties and microstructure variations induced by electric current stressing was estimated, and the mechanisms behind were further disclosed in this research. The HRTEM figures, which showed the increasing dislocation density after current stressing, indicated that electron wind force contributed to the distortion of lattice structure and the generation of dislocation. The result of EBSD showed the variations in grain size and grain orientation. The fraction of fine grain is generally raised under all current stressing conditions. Grain refinement and grain growth were respectively observed at low current density (5500 A/cm²，6500 A/cm²)and high current density(7500 A/cm²). Grain refinement was attributed to the formation of dislocation as nucleation site, along with the current-induced Joule heat which promotes recrystallization behavior. In general, all the electric current stressing conditions investigated were found to enhance the micro-hardness and lower the sheet resistance of the Sn strips. The improvement of micro-hardness could be attributed to the grain boundary strengthening and strain strengthening. The drop of sheet resistance could be attributed to the variation in grain orientation.

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