采用TEM, SEM, 硬度及电导率测试等手段, 研究了Cu-2.1Fe合金在不同温度长期时效后析出相形貌和合金性能的变化. 结果表明, 500 ℃为合金最佳时效温度, 峰时效硬度平台期较长. 合金峰时效时g-Fe粒子平均直径约12 nm, 且与基体完全共格. g-Fe粒子长大后会渐渐失去共格效应且方形化, 粗化规律符合Lifshitz-Slyozov-Wagner (LSW)规律, 粗化激活能为222 kJ/mol. Fe粒子的时效强化效果不显著, 最大强度增量约100 MPa. Cu-2.1Fe合金欠时效时遵循的强化机制为共格强化机制, 合金过时效后强化机制为Orowan强化机制, 理论预测与实验结果符合良好.

As one of the most widely used integrated circuit (IC) lead frame materials, Cu-2.1Fe alloy (C19400) shows excellent comprehensive properties, such as 90° bend fatigue, 90° bend formability, corrosion-proof, solder ability and resistance of solder peeling off. As a successful medium-strength and high-conductivity copper alloy, the Cu-2.1Fe alloy is strengthened by precipitation hardening and work hardening. Metastable coherent g-Fe particles will precipitate from supersaturated copper matrix during aging. The effects of long-term aging at different temperatures on the g-Fe coarsening characteristics and the mechanical properties of Cu-2.1Fe alloy were investigated, by means of conventional TEM, SEM, hardness, tensile strength and electrical conductivity testing. The results show that solution-treated Cu-2.1Fe alloys can reach its peak hardness and maintain for a longer time when aging at 500 ℃. The maximum of strength occurred at a particle size of about 12 nm in mean diameter. The coarsening kinetics of g-Fe follows Lifshitz-Slyozov-Wagner (LSW) theory and the activation energy for growth is estimated to 222 kJ/mol. Furthermore, it is found that coherent Fe particles gradually evolve into semi-coherent and cubical particles after aging for a long time and at high temperatures. The aging strengthening effect of Fe particles is not significant, and the maximum increment of stress is about 100 MPa. The strengthening mechanism of undeformed Cu-Fe alloy is coherency strengthening during the under-aged stage and changes to Orowan mechanism during the over-aged stage. Experimental results are in agreement with theoretical predictions.