(天津大學 材料科學與工程學院, 天津300072)
摘 要: 在Bi-Sn、 Bi-In、 Sn-In二元相圖的基礎上, 設計出系列Bi-Sn-In控溫易熔合金, 并對合金的熔點、 相組成和釬焊接頭的力學性能進行了研究。結果表明： 低銦含量的Bi-Sn-In合金由Bi、 β-Sn和InBi相組成; 隨Sn、 In含量的增加, 易熔合金的相組成向BiIn、 BiIn2和γ(InSn4)轉(zhuǎn)化; 合金的固相線、 液相線隨Bi含量或Bi/In的增大而提高, 且當Sn含量（質(zhì)量分數(shù)）為17%時合金的液相線最低; 易熔合金的硬度隨Bi含量或Bi/In的增加而線性增大, 但隨Sn含量、 In含量的增加而降低; 提高合金的Sn含量和Bi/In, 可使合金釬焊接頭的剪切和抗拉強度得到明顯的改善; 42.6Bi-17.0Sn-40.4In合金的熔點、熔程和釬焊接頭的力學性能與50.0Bi-25.0Pb-2.5Sn-12.5Cd伍德合金相當, 符合72 ℃自動滅火灑水噴頭感溫元件的要求。
關鍵字: 無鉛焊料; 易熔合金; 熔點; 力學性能; 感溫元件
LI Shun-cheng, LIU Zhen-hua
（School of Materials Science and Engineering,
Tianjin University, Tianjin 300072, China）
Abstract: Series of Bi-Sn-In ternary fusible alloys were designed based on Bi-Sn, Bi-In and Sn-In phase diagrams, and the melting temperature, phase composition and mechanical properties of these alloys were measured and determined. The results show that Bi-Sn-In ternary fusible alloy with low content of indium consists of Bi, β-Sn and InBi phases. With increasing content of indium and tin in fusible alloy, the phase components turn to BiIn, BiIn2 and γ (InSn4) phases. The solidus and liquidus of alloys increase linearly with increasing content of bismuth or the ratio of Bi to In, and there is a minimum solidus at 17% Sn(mass fraction). Fusible alloys with higher content of bismuth or higher ratio of Bi to In have a higher hardness, whereas the contents of indium and tin have opposite effect. Meanwhile the shear and tensile strengths of soldering joints can be improved by the promotion of tin content and the Bi/In ratio in Bi-Sn-In alloy. The melting temperature and mechanical properties of 42.6Bi-17.0Sn-40.4In alloy are comparable to those of 50.0Bi-25.0Pb-12.5Sn-12.5Cd Wood alloy, and can be used as the material for 72 ℃ thermal actuator in automatic sprinkler instead of Wood alloy.
Key words: lead-free solder; fusible alloy; melting temperature; mechanical property; thermal actuator
